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  1. #601
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by Yody View Post
    Well the current wide rims with normal tires do not make for tons of traction if you actually lean the bike over hard, as you roll right past those side knobs.....

    I'm not completely discounting them. Im just saying that this new trend of people who think these wide rims and the best thing since suspension forks are not looking at this from all angles.
    Quote Originally Posted by Lelandjt View Post
    ^This. In skiing there is gear that helps intermediates do the best they ever have but holds back experts. There is gear that experts love but intermediates struggle with (I'm talking straight, stiff skis and stiff boots). Soft suspension and overly wide rims fit in the former category in the MTB world. Pros use firm suspension and rims that create a rounder tire shape. Pick the gear that works best for you and enjoy the ride. The "hype" would be believing that one thing is best for everyone and every condition.
    There's definitely a sweet spot with rim width and appropriate tire selection and I feel that the sweet spot currently for most AM and DH tires is the 23-30mm rim width range. Most Important is tire selection based on rim width and intended use. I also like my 45mm wide rims with the 29+ tires on my rigid 29r! There is no one rim tire combo that works for everything and that's the bottom line!

    It's no different with skis, bindings and boots. Big area days with big lines and big snow is best enjoyed with big skis and boots. If I'm logging big vert and long BC days I'm not going to ski my biggest skis or boots! Ski mountaineering objectives are even more select with the lightest setup to ski technical lines. There is no one is best for everything and don't kid yourself thinking that wide rims and big tires are good for do it all that won't happen.
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  2. #602
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    Quote Originally Posted by cycloxer13 View Post
    We need some new tires designed specifically for wide rims. Fortunately that is doable. It's a huge opportunity for the tire manufacturers. Everyone loves throwing on a fresh set of rubbers and even the most expensive tire don't break the bank.
    Tires wider than 2.4 don't clear many mid travel forks and frames. So even if we are headed back towards 3", it can't happen overnight. And of course with fat bikes, there is an established limit. A 27.5 DH tire probably will not get near fat bike size.

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    Quote Originally Posted by Alias530 View Post
    My dilemma is--is going from 24->30mm internal going to be worth the ~9% weight penalty or should I stick with 24mm for trail riding?
    Very tough question. I personally went with 25 internal until we get some wide-specific tires on the market. I was also worried about frame/fork clearances.
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    Quote Originally Posted by cycloxer13 View Post
    Very tough question. I personally went with 25 internal until we get some wide-specific tires on the market. I was also worried about frame/fork clearances.
    I have a Pike on a Stumpjumper Evo, tons of clearance here. Typically run a DHF 29x2.5 up front and DHR2 29x2.3 or Ardent 29x2.25 in the back depending on the time of year.

    I have no issues with traction as-is but if wide rims are as much of an improvement as tubeless or dropper posts were for me, I don't want to miss out on wide rims. But if they're just nonsense hype, I'd rather save the weight.

  5. #605
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    You only need to take a few rides on a fat bike to understand what wide tires and rims can do - particularly if you are not racing and just trail/mtn riding for fun. Do you want ultimate grip or ultimate speed? It is a balance, of course. We are nowhere near optimal shape right now for traditional mtb's being ridden for fun, imho. Seriously, I laugh when I see 'normal' mtb rim/tire setups. They look so stupid and wrong.
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  6. #606
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    Quote Originally Posted by cycloxer13 View Post
    You only need to take a few rides on a fat bike to understand what wide tires and rims can do - particularly if you are not racing and just trail/mtn riding for fun. Do you want ultimate grip or ultimate speed? It is a balance, of course. We are nowhere near optimal shape right now for traditional mtb's being ridden for fun, imho. Seriously, I laugh when I see 'normal' mtb rim/tire setups. They look so stupid and wrong.
    I say with wide rims you can have both. The lower pressures allow you to roll over rough terrain easier, allowing to to roll faster in a straight line. Maybe if you get into fat bikes that changes, I don't know. But, with a 40mm external width rim, with the proper tire, I don't see any negatives at all. I take that back, if your going from a narrow carbon to wide carbon, it'll be heavier. But, most people are going from a narrow aluminum rim to a wide carbon rim and saving some weight at the same time.

  7. #607
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by Mountain Cycle Shawn View Post
    I say with wide rims you can have both. The lower pressures allow you to roll over rough terrain easier, allowing to to roll faster in a straight line. Maybe if you get into fat bikes that changes, I don't know. But, with a 40mm external width rim, with the proper tire, I don't see any negatives at all. I take that back, if your going from a narrow carbon to wide carbon, it'll be heavier. But, most people are going from a narrow aluminum rim to a wide carbon rim and saving some weight at the same time.
    Like I've stated before I like my 30mm wide IW rims and I feel the current selection of tires for this rim width works pretty well. If you think that dropping tire pressure and increasing the area of contact patch is going to make you faster in a straight line then you're smoking crack because that's not anywhere near the truth. I do believe that lower tire pressures as a result of wider rim and tire combos can yield better handling, more control and make you faster overall but it's not by making your bike roll faster.
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  8. #608
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    Quote Originally Posted by manitou2200 View Post
    Like I've stated before I like my 30mm wide IW rims and I feel the current selection of tires for this rim width works pretty well. If you think that dropping tire pressure and increasing the area of contact patch is going to make you faster in a straight line then you're smoking crack because that's not anywhere near the truth. I do believe that lower tire pressures as a result of wider rim and tire combos can yield better handling, more control and make you faster overall but it's not by making your bike roll faster.
    Wide rim/lower pressure means more traction from tires that roll faster then what you used before but don't provide enough traction for your terrain when used with skinnier rims. Kind of roundabout but still the same faster rolling outcome. Like the rolling difference between a Racing Ralph you can use now when you had to use a slower rolling Nobby Nic on a skinny.

    You could maybe pedal more too.

  9. #609
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by eb1888 View Post
    Wide rim/lower pressure means more traction from tires that roll faster then what you used before but don't provide enough traction for your terrain when used with skinnier rims. Kind of roundabout but still the same faster rolling outcome. Like the rolling difference between a Racing Ralph you can use now when you had to use a slower rolling Nobby Nic on a skinny.
    What??? That combo won't allow you to roll faster but you maybe able to carry more speed through twisty and rough terrain thus making you faster overall but it not because of lack of rolling resistance as you state. Your tire comparison is also a moot point larger contact patch through lower pressure yields higher rolling resistance. That's why you'll have more traction!
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  10. #610
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    Sounds like you need to do a little more testing.

  11. #611
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    Quote Originally Posted by Mountain Cycle Shawn View Post
    I say with wide rims you can have both. The lower pressures allow you to roll over rough terrain easier, allowing to to roll faster in a straight line. Maybe if you get into fat bikes that changes, I don't know. But, with a 40mm external width rim, with the proper tire, I don't see any negatives at all. I take that back, if your going from a narrow carbon to wide carbon, it'll be heavier. But, most people are going from a narrow aluminum rim to a wide carbon rim and saving some weight at the same time.
    Quote Originally Posted by manitou2200 View Post
    What??? That combo won't allow you to roll faster but you maybe able to carry more speed through twisty and rough terrain thus making you faster overall but it not because of lack of rolling resistance as you state. Your tire comparison is also a moot point larger contact patch through lower pressure yields higher rolling resistance. That's why you'll have more traction!
    Rough terrain is what I said. They sure don't make you roll or carry less speed.

  12. #612
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by eb1888 View Post
    Sounds like you need to do a little more testing.
    I don't think so buddy! Have you any experience with any of what we're talking about here or are you just theorizing this stuff you post?

    I'll wager I have and had more wheel and tire combos than you'll ever ride in your lifetime.

    I'm saying for most of the type of riding I do I think I'm faster on the wider rim tire combos with slightly lower pressure but it's not because of lower rolling resistance and it also not because of using a less aggressive tire like a Racing Ralph. LOL
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  13. #613
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    I'm faster on my 35/30 rim/tire combo because of better traction for sure. And I haven't noticed more rolling resistance from lower pressure and larger contact patch.. That's where our testing results seem to differ.
    But I haven't yet tried to go even faster on a tire I couldn't get enough traction from on a 21mm ArchEx but which was a slightly faster rolling tire than I am using now. I will try that combo, or actually a Thunder Burt instead of a Racing Ralph when the snow is gone this season. And on the pedaling, I can probably go faster with my present combo because of the increased traction by just pedaling more and taking more speed into the corners.

  14. #614
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    Wide Rims? Don't believe the hype...

    9%? Just how many ounces are you talking? Go with a light carbon build and you won't be gaining any weight.


    EBenke

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    Quote Originally Posted by ebenke View Post
    9%? Just how many ounces are you talking? Go with a light carbon build and you won't be gaining any weight.


    EBenke
    I did the percentage in my head, but it turns out it's actually 7.7%

    420g for the 30mm internal width rim or 390g for the 24mm internal width rim. Both Light Bicycle carbon rims. Compared to the whole bike and the rider and everything, 2 ounces is nothing, but it is on the rim, which arguably matters most.

    I knew a guy who used to drag race and he would take out his CD player, empty his coin tray, etc to get a faster time and that's WAY less in proportion to a car so it's not THAT crazy to at least discuss the difference of 60g of rim weight.

  16. #616
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    The Nextie NXT29H06 (25mm ID) weigh 380 grams. That is pretty light for a moderately wide rim.
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  17. #617
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    A lot of LB breakages out there.

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    I'm considering the LB 38mm rims, 31.6mm internal... But wondering if that's too wide for a 2.25 ardent.

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    Quote Originally Posted by rfxc View Post
    I'm considering the LB 38mm rims, 31.6mm internal... But wondering if that's too wide for a 2.25 ardent.
    I hope not... I'm about to order 30mm internal width rims and I run an Ardent 2.25 in the back in the summer.

  20. #620
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    Quote Originally Posted by manitou2200 View Post
    larger contact patch through lower pressure yields higher rolling resistance.
    This is incorrect.
    In general overall rolling efficiency goes up (resistance goes down) as pressure goes down on rough surfaces.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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    Quote Originally Posted by meltingfeather View Post
    This is incorrect.
    In general overall rolling efficiency goes up (resistance goes down) as pressure goes down on rough surfaces.
    There has to be a point where the curve changes directions though... if pressure gets too low, you're fighting the sidewall constantly crumpling.

    I ran my cross bike at the max recommended pressure for the tire on the stock rims... when I went wide (17mm stock - > 22mm... wide for a CX bike anyway ), I ran 5psi less but the tire didn't look nearly-flat under my heavy self lol

  22. #622
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    Quote Originally Posted by Alias530 View Post
    I hope not... I'm about to order 30mm internal width rims and I run an Ardent 2.25 in the back in the summer.
    I run an Ardent 2.25 on my LB 35-O/30-I rim no problem. I do think the 2.25" ardent is too narrow for my Derby 40-O rim however although I know some guys who run 2.25 on their Derbys.

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    Quote Originally Posted by Mountain Cycle Shawn View Post
    A lot of LB breakages out there.
    I can attest to 2 broken LB rims.. The first one of their hooked older versions they replaced no questions asked (I paid ~$50 for shipping). The 2nd they offered me a $15 credit on my next order. To be fair I dinged a rock pretty hard, but I don't think it should have cracked through the way it did. On principle I may not be able to order from LB again. Won't go back to AL rims tho.

  24. #624
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by Brian Damage View Post
    I can attest to 2 broken LB rims.. The first one of their hooked older versions they replaced no questions asked (I paid ~$50 for shipping). The 2nd they offered me a $15 credit on my next order. To be fair I dinged a rock pretty hard, but I don't think it should have cracked through the way it did. On principle I may not be able to order from LB again. Won't go back to AL rims tho.
    Similar story. I've had 6 LB rims in my household, broke two racing enduro/ dh at keystone in 2013 (prior to their hookless offerings). Learned my lesson.
    I'll always have an alum set around for my roughest days, but the carbon stiffness and weight is so addictive...

  25. #625
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    And the air pressure you were running when you all broke your LB rims was...?

  26. #626
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    Quote Originally Posted by ColinL View Post
    And the air pressure you were running when you all broke your LB rims was...?
    Lower than it should have been
    Both were rear wheels. I usually run 30 psi but figure I was down around 25 when it happened

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    This thread is folding back on itself. About 75 posts ago I said I was used to seeing carbon rims-- especially LB rims-- blow up at races more often than alloy, and that I'd had quite a few gravity riders (DH/enduro) who had tried very-wide rims mention to me that they closed down the shoulder lug spacing on their tires. Then some of the typical MTBR math police swarmed me because I couldn't "prove" anything I was saying, and because "racers don't know anything about the bikes they ride" compared to engineers (presumably, these were engineers).

    Now we've got a tire designer and a wheel manufacturer confirming the importance of "rim size to tire" relationship, as well as the shoulder lug orientation issue if your rim is too wide, and a bike racer mentioning their LB carbon rims blew up easier than they should have.

    I guess we'll wait for the all-knowing ones to chime in and let us all know how wrong we are, again.

  28. #628
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    Quote Originally Posted by JLF1200 View Post
    This thread is folding back on itself. About 75 posts ago I said I was used to seeing carbon rims-- especially LB rims-- blow up at races more often than alloy, and that I'd had quite a few gravity riders (DH/enduro) who had tried very-wide rims mention to me that they closed down the shoulder lug spacing on their tires. Then some of the typical MTBR math police swarmed me because I couldn't "prove" anything I was saying, and because "racers don't know anything about the bikes they ride" compared to engineers (presumably, these were engineers).

    Now we've got a tire designer and a wheel manufacturer confirming the importance of "rim size to tire" relationship, as well as the shoulder lug orientation issue if your rim is too wide, and a bike racer mentioning their LB carbon rims blew up easier than they should have.

    I guess we'll wait for the all-knowing ones to chime in and let us all know how wrong we are, again.
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  29. #629
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    I think wide carbon rims are here to stay and I think they will only get better. I'm just waiting for wide-design tires to hit the market. We're just going through some growing pains. There is still so much potential and room for improvement

    Fwiw, I am running carbon rims on my road bike, my mtn bike, my fat bike, and I used to have them on my cyclocross race bike. Other than a broken Spinergy circa 2005, I have yet to break any of the newer carbon offerings. I do weigh 142#, but I don't see myself ever riding an aluminum rim again. The carbon offerings simply superior, imho.
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  30. #630
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    Quote Originally Posted by cycloxer13 View Post
    I think wide carbon rims are here to stay and I think they will only get better. I'm just waiting for wide-design tires to hit the market. We're just going through some growing pains. There is still so much potential and room for improvement

    Fwiw, I am running carbon rims on my road bike, my mtn bike, my fat bike, and I used to have them on my cyclocross race bike. Other than a broken Spinergy circa 2005, I have yet to break any of the newer carbon offerings. I do weigh 142#, but I don't see myself ever riding an aluminum rim again. The carbon offerings simply superior, imho.
    I'd say you're right. But the thread was originally started to discuss the viability of extra-wide rims in DH racing-- curious that we don't see them anywhere, from the World Cup on down. This suggests that there are limits to the "awesomeness" that virtually all of the average joe consumers report about switching to Derby or LB rims. I, among others on the thread, offered some reasons why the rims just don't work for riders who, on average, go faster and demand more from their tires. Those ideas were countered with shouts of "BLASPHEMY!" and other such sore-ego outrage, along with "bike racers don't know much about their own bikes" as an alternative explanation of wide rim absence in DH. So the opposing school of thought basically held that the world's fastest downhillers, and their mechanics, and the engineers who support them, and the corporate component firms invested in their riders winning at all costs, were all clueless. I'm just reiterating this in case the trolls return, and so newcomers to the thread understand why the thread seems to have a suspicious tone even while the wide rim trend has been improving the stoke for the vast majority of consumers who buy in.

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    ... Oh, and my personal favorite was the explanation that DH racers are slow to adopt new technologies.

  32. #632
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    Wide Rims? Don't believe the hype...

    I wouldn't touch LB with a 10' pole, way too many failures. I went with Derby's and saved weight going with Sapim CX Ray Spokes.


    EBenke
    Last edited by ebenke; 03-03-2015 at 10:55 PM.

  33. #633
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by meltingfeather View Post
    This is incorrect.
    In general overall rolling efficiency goes up (resistance goes down) as pressure goes down on rough surfaces.
    Sorry but this is so far off its funny! All things being equal in a straight line as you lower air pressure in a tire and increase the contact patch, rolling resistance will increase. There isn't any way that you can explain the contrary!

    I stated earlier that given terrain changes with twists, turns and berms and direction changes you will most likely be faster because of the increase in traction but it will not be because of lower rolling resistance. I do know this from personal experience with repeats over the same terrain.
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by Alias530 View Post
    I hope not... I'm about to order 30mm internal width rims and I run an Ardent 2.25 in the back in the summer.
    Quote Originally Posted by Brian Damage View Post
    I run an Ardent 2.25 on my LB 35-O/30-I rim no problem. I do think the 2.25" ardent is too narrow for my Derby 40-O rim however although I know some guys who run 2.25 on their Derbys.
    The Ardents are a high volume tire but given a 30+mm IW the 2.25 size is less ideal as a front tire. It's ok as a rear tire but you should really run the 2.4 Ardent or another HV 2.35 tire like the Hans Damf, Trail King or Nobby Nic on the front.
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  35. #635
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    Quote Originally Posted by Mountain Cycle Shawn View Post
    A lot of LB breakages out there.
    2 obvious things

    1. You need to know how they many they sell - there have been 6 LBS, 2 nextie , and 2 enves bought in my riding group in 2014, one broken LB rim by the most aggressive rider in the group. Never even seen a derby or ibis rim anywhere , not even in big event races.

    2. The guy who cracked a rim, was also running 5psi than he used to with alu rims.

    So the big freaking pink elephant in the room - is stop telling people they can run super low pressures on their carbon rims. Dog knows how many rims have been busted because of the rubbish advice that comes out of forums such as these.

    Widish rims are awesome, but they don't suspend physics, even for derby

  36. #636
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    Quote Originally Posted by JLF1200 View Post
    I'd say you're right. But the thread was originally started to discuss the viability of extra-wide rims in DH racing-- curious that we don't see them anywhere, from the World Cup on down. This suggests that there are limits to the "awesomeness" that virtually all of the average joe consumers report about switching to Derby or LB rims. I, among others on the thread, offered some reasons why the rims just don't work for riders who, on average, go faster and demand more from their tires. Those ideas were countered with shouts of "BLASPHEMY!" and other such sore-ego outrage, along with "bike racers don't know much about their own bikes" as an alternative explanation of wide rim absence in DH. So the opposing school of thought basically held that the world's fastest downhillers, and their mechanics, and the engineers who support them, and the corporate component firms invested in their riders winning at all costs, were all clueless. I'm just reiterating this in case the trolls return, and so newcomers to the thread understand why the thread seems to have a suspicious tone even while the wide rim trend has been improving the stoke for the vast majority of consumers who buy in.
    I think one reason is that DH tires are much heavier and stronger then the light tires that all of us trail and AM riders use. Maybe that type of tire just doesn't need a wide rim, and maybe they just don't work any better with wide rims.

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    I think the DH'ers are worried about impact strength. DH'ers also benefit the least from a light rim, though I think they could benefit the most from a wie rim with a matching tire. It takes time to perfect new technologies. Consider what you could buy for mtb carbon rims only 3 years ago - not much. The pace of change is actually quite rapid in this space.
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  38. #638
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by manitou2200 View Post
    Sorry but this is so far off its funny! All things being equal in a straight line as you lower air pressure in a tire and increase the contact patch, rolling resistance will increase. There isn't any way that you can explain the contrary!

    I stated earlier that given terrain changes with twists, turns and berms and direction changes you will most likely be faster because of the increase in traction but it will not be because of lower rolling resistance. I do know this from personal experience with repeats over the same terrain.
    You need to educate yourself.
    This topic has been discussed exhaustively on this forum. The main mechanism is that lower pressure allows the bike and rider to roll "through" irregularities in the trail rather than firmer tires causing bumps in the trail to actually lift the rider and bike (using momentum). Lifting a 150-lb. bike+rider and not recovering that momentum robs quite a bit more energy than the hysteresis of the tire deflection, which is obvious once you look at the work that has been done on this topic.
    Then again, if you're a disciple of your own opinion and think your experience establishes the laws of the universe, you will be impermeable to facts.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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    Quote Originally Posted by manitou2200 View Post
    Sorry but this is so far off its funny! All things being equal in a straight line as you lower air pressure in a tire and increase the contact patch, rolling resistance will increase. There isn't any way that you can explain the contrary!

    I stated earlier that given terrain changes with twists, turns and berms and direction changes you will most likely be faster because of the increase in traction but it will not be because of lower rolling resistance. I do know this from personal experience with repeats over the same terrain.
    It may be counter intuitive, but it is well established that on rough terrain, rolling resistence is REDUCED with lower pressures. You can Google it, but that is not arguable as it has been exhaustively tested.

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    Quote Originally Posted by Haymarket View Post
    It may be counter intuitive, but it is well established that on rough terrain, rolling resistence is REDUCED with lower pressures. You can Google it, but that is not arguable as it has been exhaustively tested.
    First. I run lower pressures 20F/24R and I believe that they give me both more traction and less rolling resistance. But, I can only find the one study by Schwalbe, which is indicative, but hardly conclusive. Are there other studies? Everything else is anecdotal, and while I agree with it I would hardly call it exhaustively tested if Schwalbe's is the only one.
    Last edited by IPunchCholla; 03-03-2015 at 08:14 AM. Reason: forgot a critical word
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  41. #641
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    Quote Originally Posted by meltingfeather View Post
    You need to educate yourself.
    This topic has been discussed exhaustively on this forum. The main mechanism is that lower pressure allows the bike and rider to roll "through" irregularities in the trail rather than firmer tires causing bumps in the trail to actually lift the rider and bike (using momentum). Lifting a 150-lb. bike+rider and not recovering that momentum robs quite a bit more energy than the hysteresis of the tire deflection, which is obvious once you look at the work that has been done on this topic.
    Then again, if you're a disciple of your own opinion and think your experience establishes the laws of the universe, you will be impermeable to facts.
    I could see this being true for a rigid bike.

    Is it actually true for a full suspension bike? It seems evident that the suspension or lack thereof in the tire is several orders of magnitude less than the (usually air) springs and dampers on the bike.

  42. #642
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    Have you tried raising the psi????

    Quote Originally Posted by JLF1200 View Post
    This thread is folding back on itself...
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by JLF1200 View Post
    I'd say you're right. But the thread was originally started to discuss the viability of extra-wide rims in DH racing-- curious that we don't see them anywhere, from the World Cup on down. This suggests that there are limits to the "awesomeness"
    There are half-witted "arguments" on both sides of this issue.
    The contention that the fact that wide rims are not prevalent right now on the World Cup circuit means there is some fundamental performance reason being one.
    I don't have an opinion on what works for somebody else on their bike, but I do respect the opinions of people who know what they're talking about, and not those of trolls like the OP who have an axe to grind and pick some topic on MTBR a as their outlet.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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    Quote Originally Posted by JLF1200 View Post
    This thread is folding back on itself. About 75 posts ago I said I was used to seeing carbon rims-- especially LB rims-- blow up at races more often than alloy, and that I'd had quite a few gravity riders (DH/enduro) who had tried very-wide rims mention to me that they closed down the shoulder lug spacing on their tires. Then some of the typical MTBR math police swarmed me because I couldn't "prove" anything I was saying, and because "racers don't know anything about the bikes they ride" compared to engineers (presumably, these were engineers).

    Now we've got a tire designer and a wheel manufacturer confirming the importance of "rim size to tire" relationship, as well as the shoulder lug orientation issue if your rim is too wide, and a bike racer mentioning their LB carbon rims blew up easier than they should have.

    I guess we'll wait for the all-knowing ones to chime in and let us all know how wrong we are, again.
    I'm with you on this. Very wide rims came and went 15 years ago. Interesting to see the trend being recycled.

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    Quote Originally Posted by meltingfeather View Post
    There are half-witted "arguments" on both sides of this issue.
    The contention that the fact that wide rims are not prevalent right now on the World Cup circuit means there is some fundamental performance reason being one.
    I don't have an opinion on what works for somebody else on their bike, but I do respect the opinions of people who know what they're talking about, and not those of trolls like the OP who have an axe to grind and pick some topic on MTBR a as their outlet.
    Geesh. Nice personal attack.

    OK, then tell us why YOU think there are no rims wider than 27mm internal width on the World Cup DH circuit, or on any of the premium DH bike specs.

    I don't have an axe to grind. I don't even hide behind my member name. I just don't see the reason to experiment with my $$ on expensive wide rims and wanted to read some opinions.

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    Melting Feather, you've been attacking me and taking this thread off topic for a year. Please take your opinions elsewhere. I don't see any information in your profile that suggests you have credibility on this topic. You haven't indicated that you have a DH bike or any DH riding experience. Experience riding your single speed around Austin or puttering around your local trails on your hei-hei 29er does not apply here.

    I didn't start this off with a half-witted argument. Here is how I clarified myself on day one of this thread, over a year ago:

    Quote Originally Posted by oldranger View Post

    That said, after a day of interesting comments, I’d like to restate my hypothesis because I think some of you missed it: the ideal rim width for DH tires on the market today is 23mm - 25mm of internal width. I started this thread in hopes there would be attempts to prove or disprove it…which in turn, help me make a good decision on a pair of wheels for my DH bike. I recognize it’s not a well justified hypothesis, and the word “ideal” oversimplifies things…but the point I’m making has not been disproven in this thread. On the contrary, a tire designer seems to (indirectly) support it and that is the only professional opinion so far on the thread. Maybe I should try to elaborate a bit on what I mean by ideal: I mean compatible with, and works optimally in conjunction with a conventional DH tire (2.3-2.5 DH casing) to provide the best possible traction for the rider without adversely impacting speed or durability. “Ideal” for DH is not: wide enough to enable dramatically low psi so the rider doesn’t perceive slip on rocks and roots and such. Or worse…so the rider can sit down comfortably.

    Let’s not dumb this down. I threw this topic out in a forum dedicated to Wheels & Tires. This discussion isn’t about preference, or Recreation vs. Racing, or how something feels. I consider myself a recreational rider. But frankly folks – if you are a “recreational rider” sitting on a $4-8K DH bike…you’re sitting on a sophisticated, carefully spec’d piece of equipment. And most of you try to go fast (I hope). Me personally: I don’t want to ignorantly do the equivalent of throwing a big ass set of Dubs on a BMW M3 just because of some hype around ‘WIDE is BETTER’ and manufacturers like I9, Atomlab, Spank, etc. wanting to sell us those things. It is a common play to penetrate a market with gimmicky products that owners can’t find as OE on some car or truck or gun or bike – under the premise it is better.

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    Quote Originally Posted by oldranger View Post
    Geesh. Nice personal attack.


    Quote Originally Posted by oldranger View Post
    OK, then tell us why YOU think there are no rims wider than 27mm internal width on the World Cup DH circuit, or on any of the premium DH bike specs.
    I'm not sure... it could be a number of things.
    Spesh team riders are rolling 30mm Traverse SL Fatties on enduro bikes (bikes they have ridden in World Cup DH events), which is new this year, so it could be a matter of time, among the other things.
    Unfortunately there's so much butt hurt around this that I'm skeptical that any productive discussion can be salvaged.

    Quote Originally Posted by oldranger View Post
    I don't have an axe to grind. I don't even hide behind my member name.
    huh?
    Quote Originally Posted by oldranger View Post
    I just don't see the reason to experiment with my $$ on expensive wide rims and wanted to read some opinions.
    You are the one who started a thread with a belligerent title and already established opinion. It looks like it has stayed true to the way it started.
    To now say all you wanted was to solicit opinions so you can make an informed decision with your hard earned chee$e is a joke.
    Who the hell is telling you what to do with your money?
    I must have missed that thread.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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    Quote Originally Posted by ColinL View Post
    I could see this being true for a rigid bike.

    Is it actually true for a full suspension bike? It seems evident that the suspension or lack thereof in the tire is several orders of magnitude less than the (usually air) springs and dampers on the bike.
    There was an article a while back, maybe on Pinkbike, in which Schwalbe and other tire manufacturers did some high-def, high-rate video of their DH tires and the suspension linkage in action.

    There is a significant delay between when your tire goes from its full radius to complete compression, and when the suspension starts to react, mostly due to stiction. Meaning, they determined that tires are hitting rocks, the rock is fully compressing the tire, and starting to rebound, before the suspension even begins to move.
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  49. #649
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    Quote Originally Posted by manitou2200 View Post
    Sorry but this is so far off its funny! All things being equal in a straight line as you lower air pressure in a tire and increase the contact patch, rolling resistance will increase. There isn't any way that you can explain the contrary!

    I stated earlier that given terrain changes with twists, turns and berms and direction changes you will most likely be faster because of the increase in traction but it will not be because of lower rolling resistance. I do know this from personal experience with repeats over the same terrain.
    Sorry, but scientific experiments would contradict your statement.

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  50. #650
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    Quote Originally Posted by pharmaboy View Post
    2 obvious things
    So the big freaking pink elephant in the room - is stop telling people they can run super low pressures on their carbon rims. Dog knows how many rims have been busted because of the rubbish advice that comes out of forums such as these.

    Widish rims are awesome, but they don't suspend physics, even for derby
    I completely agree. Others can disagree, but when/if they break a rim, they probably should try more air pressure in the tire afterwards. The air you need is different.

    Quote Originally Posted by Le Duke View Post
    Sorry, but scientific experiments would contradict your statement.

    Wider is faster! | Schwalbe North America
    I had not seen that, thank you. The summary is quite vague; we don't know what consists of 'road' as you would think that it's not just asphalt or concrete, most gravel roads probably behave the same as well. What about a groomed BMX track?

    But on singletrack, we use the least air pressure that keeps the rim from making contact with roots and rocks, and if tubeless, not burping air when cornered hard. That's going to give the most traction and the least rolling resistance.

    People get into trouble when they guess wrong on what's the least pressure they can run, and they damage or destroy rims.

  51. #651
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    Quote Originally Posted by ColinL View Post
    I completely agree. Others can disagree, but when/if they break a rim, they probably should try more air pressure in the tire afterwards. The air you need is different.
    This is far too rational.

    Quote Originally Posted by ColinL View Post
    I had not seen that, thank you. The summary is quite vague; we don't know what consists of 'road' as you would think that it's not just asphalt or concrete, most gravel roads probably behave the same as well. What about a groomed BMX track?
    Here is a more complete paper.
    In general the smoother the surface the less the effect until some roughness tipping point where the relationship flips (resistance decreases with increasing pressure).

    Quote Originally Posted by ColinL View Post
    But on singletrack, we use the least air pressure that keeps the rim from making contact with roots and rocks, and if tubeless, not burping air when cornered hard. That's going to give the most traction and the least rolling resistance.
    Another limiting factor for a lot of riders is squirm in corners.

    Quote Originally Posted by ColinL View Post
    People get into trouble when they guess wrong on what's the least pressure they can run, and they damage or destroy rims.
    Or worse, get injured. When the penalty for failure is high, approach with caution (IMO).
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  52. #652
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    More:

    http://www.mtbonline.co.za/downloads...llustrated.pdf

    Edit: That M-Fer MF beat me to it.
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  53. #653
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    There is a reason that many World Cup XC racers are running tubulars: They can run lower pressure with very little to no chance of a pinch flat, and little chance of rim damage.

    If the most competitive mountain bike racers in the world are running 1.5bar for speed and grip purposes, perhaps there's something to it.
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  54. #654
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    Quote Originally Posted by Le Duke View Post
    There is a reason that many World Cup XC racers are running tubulars: They can run lower pressure with very little to no chance of a pinch flat, and little chance of rim damage.

    If the most competitive mountain bike racers in the world are running 1.5bar for speed and grip purposes, perhaps there's something to it.
    And theyre also running their seats up their arse, should I do that as well?
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    Proper seat height.

    They don't use droppers because they feel they don't need them. You may run your seat low because you think it looks cool; they run what is proven to allow them the most comfort while producing the most power.

    It should be noted that many/most of them run droppers on their trail/AM bikes.
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  56. #656
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    Quote Originally Posted by meltingfeather View Post
    I don't have an opinion on what works for somebody else on their bike, but I do respect the opinions of people who know what they're talking about, and not those of trolls like the OP who have an axe to grind and pick some topic on MTBR a as their outlet.
    This behavior like that of the OP usually stems from the fact that they can't or don't want to keep spending the money to constantly upgrade their bike with better technology. Along with the fact that they have never tried or even seen what they are all against. These threads pop up everytime some big change comes along. 99% of the time 99% of us end up embracing the change in the long run. The other 1% are still riding rigid bikes with long stems, rim brakes and steep geometries.

  57. #657
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    Quote Originally Posted by Le Duke View Post
    Proper seat height.

    They don't use droppers because they feel they don't need them. You may run your seat low because you think it looks cool; they run what is proven to allow them the most comfort while producing the most power.

    It should be noted that many/most of them run droppers on their trail/AM bikes.
    Yeah, who needs a high seat height on a DH run?

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    Quote Originally Posted by Le Duke View Post
    There is a reason that many World Cup XC racers are running tubulars: They can run lower pressure with very little to no chance of a pinch flat, and little chance of rim damage.

    If the most competitive mountain bike racers in the world are running 1.5bar for speed and grip purposes, perhaps there's something to it.
    XC bikes these days might as well be hybrids.....oh wait.

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    Quote Originally Posted by turbodog View Post
    XC bikes these days might as well be hybrids.....oh wait.

    XC Bike Checks: 4 World Cup Race Machines - Pinkbike
    How does it feel to know that you'd get stomped into the ground by guys on "hybrids"?
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    Quote Originally Posted by turbodog View Post
    XC bikes these days might as well be hybrids.....oh wait.

    Wait until they start showing up with wide carbon rims and even lighter tires...it's coming...hybwide
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    Quote Originally Posted by manitou2200 View Post
    The Ardents are a high volume tire but given a 30+mm IW the 2.25 size is less ideal as a front tire. It's ok as a rear tire but you should really run the 2.4 Ardent or another HV 2.35 tire like the Hans Damf, Trail King or Nobby Nic on the front.
    I'm considering a minion dhf 2.3 as a front tire-- hoping it will work on the 31.6 internal rim from LB.

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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by meltingfeather View Post
    You need to educate yourself.
    This topic has been discussed exhaustively on this forum. The main mechanism is that lower pressure allows the bike and rider to roll "through" irregularities in the trail rather than firmer tires causing bumps in the trail to actually lift the rider and bike (using momentum). Lifting a 150-lb. bike+rider and not recovering that momentum robs quite a bit more energy than the hysteresis of the tire deflection, which is obvious once you look at the work that has been done on this topic.
    Then again, if you're a disciple of your own opinion and think your experience establishes the laws of the universe, you will be impermeable to facts.
    It's the other way around dude! Either that or your reading comprehension is very poor. You seem to be referring to the dynamic qualities of what lower air pressure can do for the handling and speed carried on a mountain bike.

    What I stated very clearly is that lower pressure as opposed to higher pressure in the same tire will create a larger contact patch. That larger contact patch will also create higher rolling resistance not lower rolling resistance!

    I do agree that the dynamic handling of most mountain bikes will be enhanced with appropriately matched rim width and tire combos inflated to an optimal psi be that lower than an over-inflated tire on the same rim. I've never stated otherwise in this thread. Optimal being the key word here whether it relates to the matching of rim width and tire size or proper inflation.
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by Haymarket View Post
    It may be counter intuitive, but it is well established that on rough terrain, rolling resistence is REDUCED with lower pressures. You can Google it, but that is not arguable as it has been exhaustively tested.
    Like I stated in my reply to MF, you also need to work on the reading comprehension!
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    Quote Originally Posted by manitou2200 View Post
    It's the other way around dude!
    Stop digging yourself into a hole and spend 5 minutes reading the links provided.
    you're wrong.
    it's been beat to death here on mtbr.
    simple.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  65. #665
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    Quote Originally Posted by manitou2200 View Post
    Like I stated in my reply to MF, you also need to work on the reading comprehension!
    It doesn't matter how good your reading comprehension is if you're reading the wrong information.

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    Quote Originally Posted by meltingfeather View Post
    Stop digging yourself into a hole and spend 5 minutes reading the links provided.
    you're wrong.
    it's been beat to death here on mtbr.
    simple.
    +100%

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    Quote Originally Posted by manitou2200 View Post
    It's the other way around dude! Either that or your reading comprehension is very poor. You seem to be referring to the dynamic qualities of what lower air pressure can do for the handling and speed carried on a mountain bike.

    What I stated very clearly is that lower pressure as opposed to higher pressure in the same tire will create a larger contact patch. That larger contact patch will also create higher rolling resistance not lower rolling resistance!

    I do agree that the dynamic handling of most mountain bikes will be enhanced with appropriately matched rim width and tire combos inflated to an optimal psi be that lower than an over-inflated tire on the same rim. I've never stated otherwise in this thread. Optimal being the key word here whether it relates to the matching of rim width and tire size or proper inflation.
    You really should read up on it...counter intuitive and different than resistance on smooth surfaces, but to argue something that has been widely disproven makes yourself look a little silly. Do a search or read the links. Effective rolling resistance is lower at lower pressures on rough terrain. Period.

  68. #668
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    Quote Originally Posted by Haymarket View Post
    You really should read up on it...counter intuitive and different than resistance on smooth surfaces, but to argue something that has been widely disproven makes yourself look a little silly. Do a search or read the links. Effective rolling resistance is lower at lower pressures on rough terrain. Period.
    Im not sure the "period" is really necessary . While it seems to be the case, there hasn't been a re run of the study to reproduce the results, and it wasn't the best quality study ever. Given there is so little info , we go with what we have, but it's a long way from a fact.

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    Quote Originally Posted by Le Duke View Post
    Sorry, but scientific experiments would contradict your statement.

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    Fat bikes, clearly, are the future of all racing disciplines!

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    Quote Originally Posted by pharmaboy View Post
    Im not sure the "period" is really necessary . While it seems to be the case, there hasn't been a re run of the study to reproduce the results, and it wasn't the best quality study ever. Given there is so little info , we go with what we have, but it's a long way from a fact.
    The "period" was really necessary!!

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    Quote Originally Posted by aerius View Post
    Fat bikes, clearly, are the future of all racing disciplines!
    No, but if you spend some time riding one, you may be enlightened by what you can do with wide tires and wide rims.

    What a lot of people are missing is that most of us are not racing. We are out there trying to have fun and enjoy mountain biking whenever we have a chance to play. Wide tires and wide rims can enhance that experience, imho, especially for the average joey who maybe doesn't have Absalon lungs nor Peat skills.

    Look, I used to race XC at a very high level. It was awesome. I loved it. However, I wouldn't want to roll around on one of those rigs to go rip some trails with my buds and my dog. XC race rigs may be fast, but they also kinda suck, are uncomfortable, and have their trail capability limits. This fall I purposely rode my Fatboy on all group rides because I wanted to understand how the bike performed. It was an enlightening experience. I just kept thinking, damn, if we could just scale down this tire/rim combo and throw it on a FS trail bike, it would be one hell of fun ride - a true winner.
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    manitou, Regardless of the Schwalbe study that (you haven't read) insists lower pressure / bigger volume are faster in rough terrain.
    Watch any XC race to see who flats. Usually it's not the big guy with the 2.3 / 2.4 tire, more often it's the light weight pushing a 2.0 /2.1 tire.
    Simple fact is very, very few people who flat ever win a race. And if just riding rough terrain who the heck wants to repair a flat?
    Once you try a big volume tubeless tire, you'll (stop arguing) and not go back.

  73. #673
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    Quote Originally Posted by Flyin_W View Post
    Once you try a big volume tubeless tire, you'll (stop arguing) and not go back.
    Haha exactly. I easily envision trail bike tires creeping up more towards 3" on wide rims. I think once the wheel-tire system is optimized the weight will either equal or even go below what most of us are riding today.
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  74. #674
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    Quote Originally Posted by cycloxer13 View Post
    Haha exactly. I easily envision trail bike tires creeping up more towards 3" on wide rims. I think once the wheel-tire system is optimized the weight will either equal or even go below what most of us are riding today.
    I don't think they'll get any fatter for trail use. The whole idea is not to have the tire so out of proportion with the rim. It's not that wide rims are better. The size proportions between the tire and the wide rim is what makes it better. If they make the tires bigger, then you'll have to chase the bigger tires with wider rims. Also, tire technology has not allowed the tire makers to make wider tires any lighter, and it doesn't make any sense to make the wheel and tire combo any heavier than it is. If you need any bigger than a 40mm wide external rim and a 2.5" tire, then you might as well get a fat bike.

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    A 2.5 on a wide rim with a more vertical sidewall, I buy it. Okay maybe I exaggerated a bit with 3, but maybe not so much for DH use.
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    Quote Originally Posted by cycloxer13 View Post
    A 2.5 on a wide rim with a more vertical sidewall, I buy it. Okay maybe I exaggerated a bit with 3, but maybe not so much for DH use.
    Yes, less is best here. Even 2.1" tires work very well with wide rims.

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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by meltingfeather View Post
    Stop digging yourself into a hole and spend 5 minutes reading the links provided.
    you're wrong.
    it's been beat to death here on mtbr.
    simple.
    I've read the Schwalbe article, I am a pretty big fan of their products and I have more of their tires than I probably should. Our difference of opinion was in the terms rough terrain vs. more smooth terrain. I was making the rolling resistance comment based on smooth terrain and never refered to rough terrain. This higher pressure bias applies to all tires on smoooth(er) terrain, mtb, road etc. Looking back at your comment I replied to, you did state rough terrain so maybe my reading comprehension was sub par here. I partially blame it on my phones small screen and the fact that I was traveling for work. LOL!

    Quote Originally Posted by Haymarket View Post
    You really should read up on it...counter intuitive and different than resistance on smooth surfaces, but to argue something that has been widely disproven makes yourself look a little silly. Do a search or read the links. Effective rolling resistance is lower at lower pressures on rough terrain. Period.
    Agreed and I am a disciple of this belief. I have been running tubeless mtb tires for over 8 years and also the lowest pressures that I can run without rim strikes.

    Quote Originally Posted by pharmaboy View Post
    Im not sure the "period" is really necessary . While it seems to be the case, there hasn't been a re run of the study to reproduce the results, and it wasn't the best quality study ever. Given there is so little info , we go with what we have, but it's a long way from a fact.
    I agree with you here! The period was and is not necessary. You have to evaluate your tire and inflation level based on the majority of the terrain you're riding. There is no one does it all!

    Quote Originally Posted by Mountain Cycle Shawn View Post
    The "period" was really necessary!!
    No it's not! Period!
    Quote Originally Posted by J.B. Weld View Post
    It doesn't matter how good your reading comprehension is if you're reading the wrong information.
    I've not read the wrong info at all. I did miss the rough terrain comment so yep my reading comprehension was well....

    Quote Originally Posted by Flyin_W View Post
    manitou, Regardless of the Schwalbe study that (you haven't read) insists lower pressure / bigger volume are faster in rough terrain.
    Watch any XC race to see who flats. Usually it's not the big guy with the 2.3 / 2.4 tire, more often it's the light weight pushing a 2.0 /2.1 tire.
    Simple fact is very, very few people who flat ever win a race. And if just riding rough terrain who the heck wants to repair a flat?
    Once you try a big volume tubeless tire, you'll (stop arguing) and not go back.
    So I own wheels with internal rim widths from 21mm through 39mm and have for more that 7 years. I have tires up to 3" wide and I don't currently run any mtb tires narrower that 2.25. I think I was a bit ahead of the wide rim big high volume tires. The only flat I've had in the last 4 years was on my 30 mm IW rim when I let my air pressure drop to around 15 psi when the temps dropped last November and I did not check the pressure before a ride. Opps!
    Function in disaster, finish in style.

  78. #678
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    Quote Originally Posted by manitou2200 View Post
    I think I was a bit ahead of the wide rim big high volume tires.
    OMG, so now you want us to believe you're some kind of visionary or renaissance man. Boy, where ever you're from, the rivers run deep, wide and fast with BS!

  79. #679
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by Mountain Cycle Shawn View Post
    OMG, so now you want us to believe you're some kind of visionary or renaissance man. Boy, where ever you're from, the rivers run deep, wide and fast with BS!
    Give it a ****ing rest dude! You have a grating personality that adds nothing to any thread on this forum.

    I never claimed to be a visionary so don't be butt hurt by my comments! Fricking internet troll boy! Do you ride or just live on this forum?
    Function in disaster, finish in style.

  80. #680
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    Quote Originally Posted by manitou2200 View Post
    I think I was a bit ahead of the wide rim big high volume tires.
    Quote Originally Posted by manitou2200 View Post
    Give it a ****ing rest dude! You have a grating personality that adds nothing to any thread on this forum.

    I never claimed to be a visionary so don't be butt hurt by my comments! Fricking internet troll boy! Do you ride or just live on this forum?
    Haha, I'm ROFLMFAO! Sure looks like you did. It sounds like you're the one who is "butt hurt".

  81. #681
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    Would you (Shawn) and you MF(er) stop talking about "butt hurt" on my thread. Start your own on that topic since you seem to know a bit about it. I am seriously disappointed this Forum allows you guys to behave like you do.

    By the way - Mr. Moderator, can you have the 'Ignore List' feature enhanced so it also blocks those Users content from my email updates. I really wish it worked that way.

    Going off-topic since it seems to be the thing to do here

  82. #682
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    ^ Are you butt chapped?

  83. #683
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    Quote Originally Posted by Mountain Cycle Shawn View Post
    ^ Are you butt chapped?
    Well, now that you mention it...I think so. Based on recommendations in this thread I've been riding with my seat height jacked up for proper pedaling position. That has caused some chafing among other problems. I suppose you will recommend a WIDER chamois in my Lycra shorts. A wider chamois must be way better for DH riding with a jacked up seat-post

  84. #684
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    nerd fight
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  85. #685
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    Quote Originally Posted by oldranger View Post
    Well, now that you mention it...I think so. Based on recommendations in this thread I've been riding with my seat height jacked up for proper pedaling position. That has caused some chafing among other problems. I suppose you will recommend a WIDER chamois in my Lycra shorts. A wider chamois must be way better for DH riding with a jacked up seat-post
    Haha, naw just quit wearing panties, lower your seat a little and you'll be fine.

  86. #686
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    Quote Originally Posted by aerius View Post
    Fat bikes, clearly, are the future of all racing disciplines!
    Quote Originally Posted by cycloxer13 View Post
    No, but if you spend some time riding one, you may be enlightened by what you can do with wide tires and wide rims.
    That was sarcasm actually, but there is a point to it. The claim of the Schwalbe study is that wider tires and low pressure is faster, but they only took it to a moderately sized tire so we don't know if/when that relationship breaks down. Anyone who's ridden a fat bike at 5psi on normal terrain (ie. not snow or sand) can tell you that it's slower than a bike with regular tires, which means that somewhere between 2.2" and 4" the wider=faster correlation breaks down and goes backwards.

    I suspect the same is true of wide rims at the current time, a 21mm rim is no doubt better than the 17mm ones I once rode, and 25mm is better than 21mm. But this does not necessarily mean that 35mm or 40mm is better than 25mm, it's entirely possible that wider=better for rims also has a point where it falls apart and is no longer true. We just don't know where that point is or if it exists because no one to my knowledge has systematically tested for it yet.

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    Couldn't agree more with Aerius' post. After hundreds of posts, there' still no non-subjective info to be had on rim width. It's been over a year since I posted the following and we're seemingly still no closer to an answer:

    Quote Originally Posted by TigWorld View Post
    ...So why isn't everyone running fatbike rims at 50mm, 70mm or 90mm wide if wider is always better? There must be some point at which "wide" becomes too-wide...

  88. #688
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    ^ Some peoples logic just amazes me. As with anything in life, there is a point of diminishing returns. Just because a couple aspirin takes away a minor headache, doesn't mean that you would take a hole bottle for a migraine. Same with wide rims. There's a point at which going wider, isn't going to be better. I haven't heard anyone who has spent a lot of time on 40mm wide rims say anything bad about them. My guess is there is no need to go any wider, unless the terrain you're riding on requires a fat bike.

  89. #689
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    After reading 28 pages I figured I'd post my impression of the wide rims discussion.

    On the good side:
    * Wide rims increase the air volume with the same size tire.
    * Wide rims support the tire better, allowing better tire support at lower air pressures and less burps.
    * Some find the lower tire pressure traction/handling quite compelling.
    * Other similar uses like offroad motorcycles have much lower tire to rim ratios, supporting the idea that low tire to rim ratios are a good thing.
    * the tire footprint gets wider and shorter (area unchanged and is directly related to load and air pressure).
    * Exactly what is wide seems unclear, but the Derby (external 40mm), Ibis 721 (external 41mm), and Nox Farlow 275 (external 35mm) seem commonly mentioned.

    However on the downside:
    * Wide rims are heavier (for the same design)
    * Lower air pressure and same ride height results in being more vulnerable to pinch flats and rim damage from small rocks and hard edges.
    * tire design is sensitive to rim size, pretty much all today popular tires are designed for non-wide rims.
    * Increased air volume means a more linear compression rate, easier to bottom out than a lower volume wheel setup.

    Seem like a reasonable summary of the thread?
    Last edited by spikebike; 03-07-2015 at 07:18 AM. Reason: minor tweak

  90. #690
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    Ibis 741 though, not 721

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    Many riders will be coming to a carbon Chinese rim as light as 390g-450g from a heavier oem wheelset or skinnier aluminum rim that weighs about the same or more.

    From my experience, a 30mm inside rim can allow you to use a lighter faster rolling tire in some terrains and still get a good performance improvement in grip and washout resistance.

    For a hardtail the bigger volume adds comfort in the rear and some small bump compliance at the front.

  92. #692
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    Quote Originally Posted by spikebike View Post
    After reading 28 pages I figured I'd post my impression of the wide rims discussion.

    On the good side:
    * Wide rims increase the air volume with the same size tire.
    * Wide rims support the tire better, allowing better tire support at lower air pressures and less burps.
    * Some find the lower tire pressure traction/handling quite compelling.
    * Other similar uses like offroad motorcycles have much lower tire to rim ratios, supporting the idea that low tire to rim ratios are a good thing.
    * the tire footprint gets wider and shorter (area unchanged and is directly related to load and air pressure).
    * Exactly what is wide seems unclear, but the Derby (external 40mm), Ibis 721 (external 41mm), and Nox Farlow 275 (external 35mm) seem commonly mentioned.

    However on the downside:
    * Wide rims are heavier (for the same design)
    * Lower air pressure and same ride height results in being more vulnerable to pinch flats and rim damage from small rocks and hard edges.
    * tire design is sensitive to rim size, pretty much all today popular tires are designed for non-wide rims.
    * Increased air volume means a more linear compression rate, easier to bottom out than a lower volume wheel setup.

    Seem like a reasonable summary of the thread?
    Yep, seems about right. Great summary.

  93. #693
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    Quote Originally Posted by spikebike View Post
    After reading 28 pages I figured I'd post my impression of the wide rims discussion...Seem like a reasonable summary of the thread?
    Excellent recap.
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    I'd say that's a pretty reasonable summary of wide rims to me.

    What I've come to the conclusion from my little bit of experimenting with WTB i25s and Velocity Dually45s with tyres from 2.25"-3", is that matching the right width rim to the right width & shape tyre is very important. For me, I think rim width should fall within a percentage of the tyres width to be used on them, but need to also take tyre profile (squarer or rounder) into consideration, but somewhere around 50-60% external measurement should give you a nice shape and lots of sidewall support to help eliminate tyre roll, allowing for lower pressures, which will give you better tyre conformation to the obstacles and hence better grip etc, etc.

    Quote Originally Posted by spikebike View Post
    After reading 28 pages I figured I'd post my impression of the wide rims discussion.

    On the good side:
    * Wide rims increase the air volume with the same size tire.
    * Wide rims support the tire better, allowing better tire support at lower air pressures and less burps.
    * Some find the lower tire pressure traction/handling quite compelling.
    * Other similar uses like offroad motorcycles have much lower tire to rim ratios, supporting the idea that low tire to rim ratios are a good thing.
    * the tire footprint gets wider and shorter (area unchanged and is directly related to load and air pressure).
    * Exactly what is wide seems unclear, but the Derby (external 40mm), Ibis 721 (external 41mm), and Nox Farlow 275 (external 35mm) seem commonly mentioned.

    However on the downside:
    * Wide rims are heavier (for the same design)
    * Lower air pressure and same ride height results in being more vulnerable to pinch flats and rim damage from small rocks and hard edges.
    * tire design is sensitive to rim size, pretty much all today popular tires are designed for non-wide rims.
    * Increased air volume means a more linear compression rate, easier to bottom out than a lower volume wheel setup.

    Seem like a reasonable summary of the thread?
    Quote Originally Posted by Harold
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  95. #695
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    This tread needs some pictures. 26" x 40mm Derby rims with Hadley hubs, DT Swiss Revolution spokes and Sapim Polyax 14mm nips, so they stick out nice and far when the weather gets cold. I'm waiting for a pair of American Classic valves. Build weight is 1690 grams.




  96. #696
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    Quote Originally Posted by LyNx View Post
    I'd say that's a pretty reasonable summary of wide rims to me.

    What I've come to the conclusion from my little bit of experimenting with WTB i25s and Velocity Dually45s with tyres from 2.25"-3", is that matching the right width rim to the right width & shape tyre is very important. For me, I think rim width should fall within a percentage of the tyres width to be used on them, but need to also take tyre profile (squarer or rounder) into consideration, but somewhere around 50-60% external measurement should give you a nice shape and lots of sidewall support to help eliminate tyre roll, allowing for lower pressures, which will give you better tyre conformation to the obstacles and hence better grip etc, etc.
    Sounds reasonable, just like the ibis page says.

    > If you look at nearly all other vehicles, the ratio of outer tire width to inner rim width is anywhere from 1.2:1 to 1.5:1.

    > Here are a few examples:
    > Road bike 1.2: 1
    > Motorcycle 1.3-1.5:1
    > Car 1.3:1
    > Mountain bike 3:1

    It's pretty clear what the outlier is.

  97. #697
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    Quote Originally Posted by spikebike View Post
    After reading 28 pages I figured I'd post my impression of the wide rims discussion...
    Nice distilling spikebike, a great post.

    It looks like the only real questions left are how much more grip and survivability we attain from a wider rim and if it is worth the thousand+ dollars to get it.

    Quote Originally Posted by spikebike View Post

    * Increased air volume means a more linear compression rate, easier to bottom out than a lower volume wheel setup.
    I'll just call this one out as unlikely for 2 reasons.

    A large ramp up or progression of the spring curve happens when the air gets compressed into a very small volume relative to it's starting volume. A tire does not reduce that much volume when it hits a rock or lands hard.

    In addition, when hitting a large square edged rock, for example, the rock's entry into the tire casing takes volume away from the tire, and increases air pressure within the tire. When the air pressure increases, the tire casing will expand a very small amount in reaction - across the entire casing - actually adding some volume.

    P

  98. #698
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    Quote Originally Posted by spikebike View Post
    * the tire footprint gets wider and shorter (area unchanged and is directly related to load and air pressure).
    this should be changed to
    * at the same pressure the tire footprint gets wider and shorter (area unchanged and is directly related to load and air pressure).
    it makes clear to understand that is the air pressure and load that change the area of the contact patch, and not the wide of the tire.

  99. #699
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    Quote Originally Posted by Mr.P View Post
    Nice distilling spikebike, a great post.


    A large ramp up or progression of the spring curve happens when the air gets compressed into a very small volume relative to it's starting volume. A tire does not reduce that much volume when it hits a rock or lands hard.

    In addition, when hitting a large square edged rock, for example, the rock's entry into the tire casing takes volume away from the tire, and increases air pressure within the tire. When the air pressure increases, the tire casing will expand a very small amount in reaction - across the entire casing - actually adding some volume.

    P
    I too appreciated spikebikes informative post!

    Wouldn't the give of the tire contribute to a worse than linear spring rate? We've got pv=nrt. We're changing v, so p should change to compensate, pushing back, but when you reduce the volume by 10% due to a big strike, the pressure would ramp up by 10% except the volume doesn't really go down 10%, since the rest of the tire is expanding, so tire pressure spikes by a smaller percentage, as if there was less air in the tire. I suspect we could put together a stochastic model, gather a bunch of data and estimate coefficients A and B, i.e., P=Bnrtv^A+random error, and we'd find that A is something like -.9 on a wider rim and maybe -.95 on a narrower rim.

    The experiment would ask how much force does it take to reduce the volume of a tire such that the rim just bottoms out. This could be conducted over a wide range of starting tire pressures. My version of the math has a lot of simplifications relative to deriving the actual expression for estimating this relationship (e.g., non-linear relationship between force and pressure due to changing contact patch), but a black box/reduced form model like this could suss it out if someone would just gather the data. That chain friction facts guy seems to be game to funding these sorts of experiments

    I'm not a physicist, just a babbling staticstician/economicst, but based on ideal gas laws, I think somethign along these lines is what we would look at to determine a non-linear/progressive/regressive spring rate. The expansion of the rim (as long as volume is rising due to the expansion) contributes (perhaps) to a regressive spring rate, and the bigger the change in volume due to a given strike causing initial tire deformation, the more the rate is regressive.

    I'm keen in particular about advice on the following:
    EDIT: this question pertains to 29+, specifically knard on rabbit hole is what I just destroyed (after 2 years (25 months), ~50 mile per week including 10 days of loaded bikepacking and a broken krampus frame)
    since we're in a thread where people are considering this sort of question carefully:
    I just destroyed my rabbit hole rim and am always constrained by the need to avoid bottoming out my tire and damaging the tire bead/sidewall junction and the rim too. Everyone I read about in my weight range (225lbs fully loaded) runs no more than 15 psi. I have to run 20 psi rear to reduce rim strikes to ~once per 50-100 miles. Tires still fail to hold tubeless at the bead from damage within 6 months of installation (all this is for rear tires only, but front tires require higher pressure for me than many other folks(~18 psi)). At the 12 psi that many 29+ riders report for rear tires, I can nearly bottom out the front rim preloading for a bunnyhop, which is scary when at speed.

    light bike has a 50mm carbon rim for $200 that is vaguely tempting, but I'd probably end up running 22psi out of fear of cracking it on a rim strike. Perhaps I should go with a 35-40mm wide rim to save money at no cost in handling since I run high pressures anyways?
    Last edited by PretendGentleman; 03-09-2015 at 02:57 PM.

  100. #700
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    Hi, interesting read. I don't know where you are getting your pressures from, but at 20lbs less than you, 22psi in the rear nearly always results in a rim strike for me. I know because I get a rim strike, then check pressure and note it's way down. I run 20psi in the front and 30psi in the rear.

    I am xc only dual suspension so often are seated for a 1" high root. Most people in xc in my riding group and around my weight are running low twenties in the front and high twenties in the rear except for one guy who is pretty aggressive who is running 30 front and high thirties rear.

    Note - my pressures are off a track pump that agrees with a schwalbe digital pressure guage

  101. #701
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    Quote Originally Posted by PretendGentleman View Post
    I just destroyed my rabbit hole rim and am always constrained by the need to avoid bottoming out my tire and damaging the tire bead/sidewall junction and the rim too. Everyone I read about in my weight range (225lbs fully loaded) runs no more than 15 psi. I have to run 20 psi rear to reduce rim strikes to ~once per 50-100 miles. Tires still fail to hold tubeless at the bead from damage within 6 months of installation (all this is for rear tires only, but front tires require higher pressure for me than many other folks(~18 psi)). At the 12 psi that many 29+ riders report for rear tires, I can nearly bottom out the front rim preloading for a bunnyhop, which is scary when at speed.

    light bike has a 50mm carbon rim for $200 that is vaguely tempting, but I'd probably end up running 22psi out of fear of cracking it on a rim strike. Perhaps I should go with a 35-40mm wide rim to save money at no cost in handling since I run high pressures anyways?
    "everyone" is either full of crap, rides nothing but sand & snow, or has defective tire pressure gauges.

    "everyone" doesn't pay for new wheels: you do. 15 psi is nowhere near enough for anything less than a fatbike.

    pharmaboy is correct, and since you just wrecked a rim, you have empirical evidence that you were not running enough air in your tires. I don't understand why you think that 22psi is a lot in a rear tire, at 225 pounds. It isn't a lot, at all.

    you're not really giving up anything. just inflate the tires more. you'll get enough traction, and more importantly, you'll destroy fewer wheels.

  102. #702
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    I just added a note to clarify this on my previous post.

    This is for my krampus running 3" knards on 50mm external width rabbit hole rims. I've had the rim through many miles and 2 rebuilds (3 different hubs as I destroyed 2 shimanos (Xt and slx) before upgrading to dt 350. For this setup, 15 psi is typical. I do have several dents in my rim from low pressures, but often due to failing tires.

    so in summary, I run higher than normal pressures for my format (29+) and am wondering if I would notice any adverse affect if I replace my 50mm wide rim with a 35-40mm rim that will cost a good bit less. I'm leaning towards replacing with the same width, but would downsize if my high pressures are likely to be erasing the benefits of a full 2" rim for 3" tires.

  103. #703
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    Quote Originally Posted by Mountain Cycle Shawn View Post
    This tread needs some pictures. 26" x 40mm Derby rims with Hadley hubs
    This is too much to handle. MC Shawn...you are building a 26" wheelset.

    These pictures are the best ever. Are you kidding me!?! You bashed others (me, the OP) for not embracing the new technology of wide rims...you wrote: "they can't or don't want to keep spending the money to constantly upgrade their bike with better technology"...and you put yourself in the "99% of us that embrace the change".

    Yet you are building up a set of 26" wheels for a trail bike. If anyone is still listening to you for advice on how to find the future of wheel design - they are hopelessly lost.

    P.S. Folks: If you are new to DH (Downhill) and trying to get something out of this thread about PSI - please go elsewhere for advice. This thread has been contributed to by folks discussing PSI for light to moderate trail riding demands where pedaling uphill and negotiating trails slowly are in consideration. There may be some good advice in there for that.

    P.P.S Folks: I'm sorry for stooping to Mr. Shawn's level of personal attacks, but it appears that is fair game on MTBR. I just want to make sure no one misses the obvious hipocrisy. Visionaries are not out building 26" wheel sets.

  104. #704
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by oldranger View Post
    This is too much to handle. MC Shawn...you are building a 26" wheelset.

    These pictures are the best ever. Are you kidding me!?! You bashed others (me, the OP) for not embracing the new technology of wide rims...you wrote: "they can't or don't want to keep spending the money to constantly upgrade their bike with better technology"...and you put yourself in the "99% of us that embrace the change".

    Yet you are building up a set of 26" wheels for a trail bike. If anyone is still listening to you for advice on how to find the future of wheel design - they are hopelessly lost.

    P.S. Folks: If you are new to DH (Downhill) and trying to get something out of this thread about PSI - please go elsewhere for advice. This thread has been contributed to by folks discussing PSI for light to moderate trail riding demands where pedaling uphill and negotiating trails slowly are in consideration. There may be some good advice in there for that.

    P.P.S Folks: I'm sorry for stooping to Mr. Shawn's level of personal attacks, but it appears that is fair game on MTBR. I just want to make sure no one misses the obvious hipocrisy. Visionaries are not out building 26" wheel sets.
    This post demonstrates what we suspected all along: you're not an honest seeker looking for dialogue. You're a petty poon tang looking to prove something. GTFO.
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    Time to stop believing the hype and start doing some science.
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  105. #705
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    Quote Originally Posted by oldranger View Post
    This is too much to handle. MC Shawn...you are building a 26" wheelset.

    These pictures are the best ever. Are you kidding me!?! You bashed others (me, the OP) for not embracing the new technology of wide rims...you wrote: "they can't or don't want to keep spending the money to constantly upgrade their bike with better technology"...and you put yourself in the "99% of us that embrace the change".

    Yet you are building up a set of 26" wheels for a trail bike. If anyone is still listening to you for advice on how to find the future of wheel design - they are hopelessly lost.

    P.S. Folks: If you are new to DH (Downhill) and trying to get something out of this thread about PSI - please go elsewhere for advice. This thread has been contributed to by folks discussing PSI for light to moderate trail riding demands where pedaling uphill and negotiating trails slowly are in consideration. There may be some good advice in there for that.

    P.P.S Folks: I'm sorry for stooping to Mr. Shawn's level of personal attacks, but it appears that is fair game on MTBR. I just want to make sure no one misses the obvious hipocrisy. Visionaries are not out building 26" wheel sets.
    Quote Originally Posted by meltingfeather View Post
    This post demonstrates what we suspected all along: you're not an honest seeker looking for dialogue. You're a petty poon tang looking to prove something. GTFO.
    Actually I liked his post. Spot on oldranger
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  106. #706
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    Quote Originally Posted by PretendGentleman View Post
    I just added a note to clarify this on my previous post.

    This is for my krampus running 3" knards on 50mm external width rabbit hole rims. I've had the rim through many miles and 2 rebuilds (3 different hubs as I destroyed 2 shimanos (Xt and slx) before upgrading to dt 350. For this setup, 15 psi is typical. I do have several dents in my rim from low pressures, but often due to failing tires.

    so in summary, I run higher than normal pressures for my format (29+) and am wondering if I would notice any adverse affect if I replace my 50mm wide rim with a 35-40mm rim that will cost a good bit less. I'm leaning towards replacing with the same width, but would downsize if my high pressures are likely to be erasing the benefits of a full 2" rim for 3" tires.
    Oh, that'd change things some. I'd go fatbikes forum for that question - nextie s are the business for fatties, not sure about the half fatty though

  107. #707
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    Quote Originally Posted by oldranger View Post
    This is too much to handle. MC Shawn...you are building a 26" wheelset.

    These pictures are the best ever. Are you kidding me!?! You bashed others (me, the OP) for not embracing the new technology of wide rims...you wrote: "they can't or don't want to keep spending the money to constantly upgrade their bike with better technology"...and you put yourself in the "99% of us that embrace the change".

    Yet you are building up a set of 26" wheels for a trail bike. If anyone is still listening to you for advice on how to find the future of wheel design - they are hopelessly lost.

    P.S. Folks: If you are new to DH (Downhill) and trying to get something out of this thread about PSI - please go elsewhere for advice. This thread has been contributed to by folks discussing PSI for light to moderate trail riding demands where pedaling uphill and negotiating trails slowly are in consideration. There may be some good advice in there for that.

    P.P.S Folks: I'm sorry for stooping to Mr. Shawn's level of personal attacks, but it appears that is fair game on MTBR. I just want to make sure no one misses the obvious hipocrisy. Visionaries are not out building 26" wheel sets.
    I have no problem with upgrading and there are no lack of funds for me to upgrade. I like the SC Nickel LT that I have and I'll upgrade to a 27.5 when this bike is thrashed. I don't upgrade just for the sake of it.

  108. #708
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by Yody View Post
    Actually I liked his post. Spot on oldranger
    Good for you. Funny that you'd feel motivated to post support for such a douchey personal attack post. Birds of a feather I guess... I guess you ride the same wheel size oldranger does, so your opinion counts or something? Hard to follow the "logic."
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  109. #709
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    The difference here is, I'm not saying that other wheel sizes are bad or they don't work well. Each has its place. I'm just not ready for a change in wheel size yet. I also haven't switched to a one ring up front. For where I ride it doesn't make sense yet.

  110. #710
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    Quote Originally Posted by meltingfeather View Post
    This post demonstrates what we suspected all along: you're not an honest seeker looking for dialogue. You're a petty poon tang looking to prove something. GTFO.
    Quote Originally Posted by meltingfeather View Post
    Good for you. Funny that you'd feel motivated to post support for such a douchey personal attack post. Birds of a feather I guess... I guess you ride the same wheel size oldranger does, so you opinion counts or something? Hard to follow the "logic."
    Thanks man for the support!

  111. #711
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    Melting Feather: im gonna call you out too. I started this thread and have had to tolerate your lack of discipline and straying off topic for a year now. It has really eroded the quality of this discussion.

    Show us a pic of you riding a proper DH bike on a race trail, or you GTFO. You have been contributing to this thread as though you are an expert and are knowledgeable on the subject, yet all indications are that you should have started your own thread on wide rims for the kind of riding you do...not DH.

    On the 'wider is better' side of the argument - I have seen some interesting pics from the Fontana Series. DT Swiss is making a 27.5 rim with a 'Gravity' label that is wider than the Ex471 that we saw the Specialized guys running last year. What are you guys seeing out there?

  112. #712
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    Don't believe the hype: Melting Feather and MC Shawn do not appear to own downhill race bikes. They also have not spoken in detail of their personal downhill-specific experience. They just don't like the way I started this thread.

  113. #713
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    Quote Originally Posted by oldranger View Post
    Don't believe the hype: Melting Feather and MC Shawn do not appear to own downhill race bikes. They also have not spoken in detail of their personal downhill-specific experience. They just don't like the way I started this thread.
    Says the one who has no experience on truly WIDE rims. At least I have experience with them at DH speeds.

  114. #714
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    Only in the truly unscientific world does experience trump understanding.

    It's this line of argument that goes, I don't understand how the eye came to being, no one has been able to explain it to me so I understand, therefore God did it, and evolution is a steaming pile.....

    Seriously, personal experience is not a level of evaluation that should hold any currency at all - it's more likely to delude than inform. That goes for both sides of the argument here. Physics and engineering can and does explain what's going on, and can predict the upsides and the downsides. Those engineers employed by multinational bike part companies hopefully get to run the show, though mtbr seems to indicate that whatever the marketing dept dreams up can also get a run for a few years untill the next big thing


  115. #715
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    Been keeping an eye on this one since the Ibis Enduro team announced that they're going to be using the 741 wide carbon wheels.
    Ibis Cycles 2015 Enduro Race Team | News | Info

    Seems like ACC isn't in on it yet since according to the March 1st post on her page she's already racing, and those are Crossmax wheels on her bike.
    https://www.facebook.com/acchausson?fref=ts

    Sponsorship related? Possibly. Or maybe wide rims aren't necessarily faster.

  116. #716
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    I believe ACC's primary sponsor is Mavic (wheels, shoes, jerseys, and (sometimes) tires). It's the first brand listed on her site and has been a long time supporter. Ibis is next followed by Formula (maybe she'll run a Formula fork in addition to brakes?).

    I remember reading on a forum after the Mojo HD3 launch that ACC was loving the traction that the wide rim provided on the front but felt that wide rear lacked the poppy playfulness that suits her riding style and what she wants from her equipment. I believe somebody mentioned she'd run a wide front and narrow rear if she could but that wouldn't pay the bills as well as rollin' on Mavic. She also seems to be doing extremely well on what she does ride.

    Sounds like another person with different views based on their skillset, how they ride, and what they ride.

  117. #717
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    Quote Originally Posted by Yody View Post
    Actually I liked his post.
    I think I did too - pretty funny
    Last edited by highdelll; 03-09-2015 at 10:50 PM.
    Honestly... ahh I give up

  118. #718
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    Quote Originally Posted by oldranger View Post
    Don't believe the hype: Melting Feather and MC Shawn do not appear to own downhill race bikes. They also have not spoken in detail of their personal downhill-specific experience. They just don't like the way I started this thread.
    You didn't post this in the DH section. This section is about wheels and tires and this thread evolved to different types of bikes and riding styles. And at times you went with it. Shit, you even took the discussion to BMX bikes. And, now you're all pissed off because the discussion has moved away from DH.

  119. #719
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    Quote Originally Posted by oldranger View Post
    P.S. Folks: If you are new to DH (Downhill) and trying to get something out of this thread about PSI - please go elsewhere for advice. This thread has been contributed to by folks discussing PSI for light to moderate trail riding demands where pedaling uphill and negotiating trails slowly are in consideration. There may be some good advice in there for that.
    Keep in mind, your original post asked about pro rider psi, and how they are going so fast on narrower rims. But all of us ride at "light to moderate trail riding" speeds compared to the pros, including yourself. So none of us can relate. We also don't have our income riding on not-flatting like the pros do. It's most likely we never come close to pushing a tire as hard as a top level pro on the world cup during a race run. None of us have anything relevant to say there.

    What you do have from this thread is a sliding scale with similar theories applying. Can a rider run less psi on a wider rim than a narrower rim with the same tire/trail/riding technique? XC = yes. DH = yes.

    No matter what, it is your duty as a mountain biker who wants the most out of their ride, is to run the lowest tire pressure possible for your own gear/terrain/riding style.

    Do I wish I could run lower than 28 psi on the rear of my SS hardtail? Bone jaringly, hell yes. But the sound and feeling is too ball shrivelling when I land a whipped huck sideways and fold the tire over when I run below 28 psi. That is on a Flow rim. So on a 30+ ID rim with a 2.2 tire, can I run a cushy 24 psi and not fold the tire over when I am getting irie? Now we are talking!

    Be thankful the thread has gone on as long as it has looking for answers. I found some here, and am thankful.

    Oh, and I'll make a crystal ball prediction for this year's WC DH races: There will be some teams running wide rims.

    P
    Last edited by Mr.P; 03-10-2015 at 08:41 AM.

  120. #720
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by oldranger View Post
    Melting Feather: im gonna call you out too.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  121. #721
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    Please resist the temptation to contribute to the trolling by defending yourself/counter-attacking. It's just not worth it, for the health of your own soul. We've all done it and probably will again, so I'm here to support your efforts to stop handing out food to unwanted trolls...

    Anybody care to update/summarize? I've been reading through multiple many-page threads as I try to talk myself out of buying carbon rims for my rim busting riding style, so I'm a little unsure what I've read in which thread.

    Is the take away from this thread as follows?: wide rims don't do much for you if you are an aggressive rider that must run high pressures to avoid serious rim strikes/damage. When you replace your wheels, go ahead and get wide rims, but don't bother upgrading just for improved performance from wide rims since you won't notice the stability benefits at higher than average psi.

    I'd like to hear the results of analysis done by physicists and engineers, but nobody is likely to pay for that and then post the results for free. We also don't know if companies are riding trends that their engineers don't like, but marketing does like. Maybe wide rims haven't showed up on pro's bikes because companies think there is more profit in delaying their use. We simply do not know. I would say the best way to understand the industry is to assume that Bike companies are profit maximizers. A bike company's goal in general is not to further mountain biking as a whole except to the extent that doing so maximizes their profits. This is why we have to guess about these complex issues and we lack a debate between trained engineers with data to backup their theories. This stuff is complex, and smart engineers would likely have disagreements.

    I run high psi's on my krampus and on all bikes have always run high pressures (45psi for 2.25" tires, 20 psi for 3"tires) because when I ride cross country I come down hard on my back wheel. I also run high front pressures because bunny hop preloading and bump-jumping big logs on a rigid bike is roughly equivalent to a 2' drop in terms of tire compression. In the fatbike forum, nobody knows about 3" tires, but everyone who isn't fat says to post my question there. ultimately I'll post in both spots until there's a plus-sized forum for us 29+, 27.5+ and 26+ converts. I am tempted by the jungle fox 50mm rim, but am mostly ok that I might kill it in 6 months, but am not ok that I might kill it on a huge ride in the mountains that will end my day of riding and require a long hike to get to a road.

  122. #722
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    I agree with just about everything you wrote right there PretendGentleman. I am in a similar place to you as a 29+ convert and also would love running carbon rims aside from the desire for durability during the long days in the saddle out in the backcountry. My philosophy is to run slightly narrower rims (35mm to 45mm) for 3 in tires and higher pressures on rides where larger impacts at higher rates of speed are probable, lowering the pressure when desired for a particular segment of trail warrants it or if a slower pace and/or compliance is desired. My preference, after running wider rims and tires is to adjust air pressure on the trail because it changes the ride significantly when you have plenty of volume to work with. Some of my DH friends have done this for years on their 26x2.5 bikes when pedaling up a long road to get to the trail, starting with a higher pressure for the long climb, then letting out a significant amount of air once they reach the trailhead. Being an xc rider primarily, I always kept my tires at pressures that would be good for all around riding, the same pressure for the entire ride since I enjoy covering as much ground as possible on each ride and dislike stopping for adjustments. I will stick to the pressure I initially start the ride with for most rides under 2 hours, but it's nice to have the option to really dial in the pressure for the intended application.
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  123. #723
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    This thread is trying to be salvaged by a few good peeps....well done!

    We should eliminate DH from this conversation, as it might be safe to say the tire technology isn't in line with a wide rim yet.

    It would be safe to assume that there are a lot of people who do enjoy/benifit from wider rims/tires. Take a look at all the happy Krampus owners out there. Yes, I understand the tires are larger in diameter, but they are also much larger in volume. I don't know of too many people in the mutiple Krampus threads that are having chronic issues with rim strikes and pinch flats.

    So if you can base your opinion on a select few users who might not be the the best at finding solutions to rim strikes or pinch flats, then you are basing your opinions on poor examples. Also take a look at all the happy P35/Blunt owners out there. Yes, some of them are getting rim strikes, but could you not conclude that at pressure required to eliminate rims strikes, the feel and performance of the tire was better?

    I am going to have to conclude that the right wheel/tire setup correctly (psi) is really going to be a lot of fun to ride. Honestly, how could you not want 35-40mm rims with tires like Maxxis Ikons (2.35) or Ardents (2.4)? Should we ever expect a 225lb rider to be able to sit on the saddle through a rock garden at 15psi on anything other than a 4" tire, and not expect rim strikes?

    I am not trying to be rude, but the first time I would experience a rim strike on a common trail feature, I would up the psi until it no longer happened....that is just common sense. Once I reached that pressure, and determined I gain no additional performance from the setup, I would then conclude that there was no benifit.

    You need to weed out the bs and remember to not base opinions on a select few. If Henry Ford did that, people would still be riding horses.

  124. #724
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    Quote Originally Posted by Mr.P View Post
    No matter what, it is your duty as a mountain biker who wants the most out of their ride, is to run the lowest tire pressure possible for your own gear/terrain/riding style...
    ...Be thankful the thread has gone on as long as it has looking for answers. I found some here, and am thankful.
    Good advice; I am in search of the lowest possible pressure myself. I am also thankful for much of the contribution to this thread.

    On PSI: I have learned through trial and error that finding the right PSI is challenging. Sometimes, I've had a different ride at top of a DH run because it is 5,000 feet higher than the base where I set my psi. Sometimes on trail rides I take the descents a bit more carefully because I'm on the low range of what can support me to get up some of the climbs. I've had my fair share of flats, but have found pressures that get me home or to the finish line 90% of the time without stopping for a flat.

    DH is part of this thread, even if just by those that read only. Note for DHers: I think it is really tough to take specific psi recommendations from internet sources. There are too many variables. Also consider:

    1) Choosing the optimal PSI for a 2 hour trail ride has got to be different than choosing PSI for a 4 minute DH race. The tires are different, and the requirements during a 2 hr trail ride with 'technical' climbing (and some very low speeds) place a far different set of demands than a typical DH race run does.

    2) On some DH tracks the lowest pressure might be dictated by a significant rock garden while on other tracks it might be dictated by pressure you need to keep the tires from folding over in high speed turns.

    3) On some DH tracks the highest pressure might be dictated by off camber, wet rooty sections that have to be done right or a crash will result. This might slow you down in the rocks and dry berms at the bottom of the track.

    In general: be careful about applying lessons learned from your trail riding to your DH bike for anything other than a starting point. For DH - you will be making decisions based on a more narrow set of requirements and might even run a different psi throughout the day if rain is in the equation. Having a good pressure gauge is one of the best tools in your toolbox.

  125. #725
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    Quote Originally Posted by oldranger View Post
    On PSI: I have learned through trial and error that finding the right PSI is challenging. ...In general: be careful about applying lessons learned from your trail riding to your DH bike for anything other than a starting point. ...
    Quoted for truth!!!

    PSI is totally subjective to the individual rider - even within a segment of riding, like DH.

    You can tell the PSI nerds - they are the ones at the trail head pumping and checking PSI right before the ride. And they will all have to bring their own pump that they are calibrated to. And they will hit a specific PSI number or it will mess with their head for the rest of the ride. Ha! (How do I know all that, ha ha)

    I have found that I feel squirmy tires in turns 2-5 psi before I am at pinchflat danger on 21-23mm ID rims. I run big tough tires and like to smash turns. My local rides also include sharp embedded shale rock in high speed downhill sections.

    P

  126. #726
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by Mr.P View Post
    PSI is totally subjective to the individual rider - even within a segment of riding, like DH.
    Wait, so we're not supposed to set PSI to what Minnaar uses?

    I'll go back to the beginning of this thread and point out that, like PSI, rim width is an individual choice best determined by riding bikes. What works or doesn't for anyone else is hardly relevant.
    Revolutionary, I know.
    If you like wide rims and they work (or even if they don't), why the need to broadcast your opinion as some sort of rule others should heed?
    Last edited by meltingfeather; 03-10-2015 at 06:05 PM.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  127. #727
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    Quote Originally Posted by meltingfeather View Post
    Wait, so we're not supposed to set PSI to what Minaar uses?
    I use Peaty's PSI, cuz I'm old school.

    P

  128. #728
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    It looks like the first wide rim tires are on the truck. Disclaimer: This link takes you to another bike site. Please return to MTBR.com ASAP for all your biking needs.
    Introduction to Project 27Plus - WTB Scraper rims and Panaracer Fat B Nimble tires

  129. #729
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    Quote Originally Posted by Mr.P View Post
    Nice distilling spikebike, a great post.

    It looks like the only real questions left are how much more grip and survivability we attain from a wider rim and if it is worth the thousand+ dollars to get it.
    Did you mean to replace a current wheelset? Or comparing a high quality normal wheelset to a high quality wide wheelset? If you are shopping for a new wheel set the premium for a ibis 741 or nox farlow doesn't seem bad when compared to similar quality wheelsets with 20-30mm wide rim wheelsets.


    Quote Originally Posted by Mr.P View Post
    I'll just call this one out as unlikely for 2 reasons.

    A large ramp up or progression of the spring curve happens when the air gets compressed into a very small volume relative to it's starting volume. A tire does not reduce that much volume when it hits a rock or lands hard.
    My main point is unlike much of the hype, the wide rims are MORE vulnerable to snake bikes than thinner rims. Even if the effect is VERY small, it's worse not better. This is made much worse if you run lower pressure which is frequently mentioned in the advantages of wide rims. So sure you get better control of the tire at lower pressures, but you are risking snake bikes and/or rim damage in the process.

  130. #730
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    Quote Originally Posted by spikebike View Post
    My main point is unlike much of the hype, the wide rims are MORE vulnerable to snake bikes than thinner rims. Even if the effect is VERY small, it's worse not better. This is made much worse if you run lower pressure which is frequently mentioned in the advantages of wide rims. So sure you get better control of the tire at lower pressures, but you are risking snake bikes and/or rim damage in the process.
    I agree with you that the smaller starting volume leads to a more progressive spring rate (but I might be using physics terms incorrectly), but I'm curious if your explanation is the same as mine. I'm not sure if folks are referencing a breakdown in ideal gas laws or just an artifact of the behavior of variables that respond to each other in percentages (in a perfect system, based on P=(nRT)V^-1, if V goes down 2%, P goes up approximately 2%~1-1/(1-.02)). This approximation breaks down for big changes, so a 20% reduction in volume causes about a 25% increase in pressure, .25%=1-1/(1-.2). So one argument, that I would have to think too hard about as someone who does not do much 3d geometry or integrals is the question of whether a wider rim vs a narrow rim experiences a larger percentage reduction in volume when experiencing a load that is just enough to cause a rim strike. I think i know how to prove the answer, but intuitively, i suspect the narrower rimmed wheel experiences a larger percentage reduction in air volume due to a rim strike, thus the spring rate is relatively more progressive than for the wide rim system.

    I am now leaning towards a 40mm rim for my krampus rear wheel. I like that I would buy a bit more flexibility on chainline and running a granny gear for huge climbs. Every mm really does count with this setup.

  131. #731
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    Quote Originally Posted by spikebike View Post
    My main point is unlike much of the hype, the wide rims are MORE vulnerable to snake bikes than thinner rims. Even if the effect is VERY small, it's worse not better. This is made much worse if you run lower pressure which is frequently mentioned in the advantages of wide rims. So sure you get better control of the tire at lower pressures, but you are risking snake bikes and/or rim damage in the process.
    I posted this a few posts above:
    I have found that I feel squirmy tires in turns 2-5 psi before I am at pinchflat danger on 21-23mm ID rims. I run big tough tires and like to smash turns. My local rides also include sharp embedded shale rock in high speed downhill sections.
    So if I can drop a few PSI, gain more grip, and not have a squirming tire all while still not striking there rim - that is a huge win. I'm not talking stupid low pressures, just 2-5 less PSI than I run now.

    Regardless, this is tubeless we are talking about, bottoming out on the rim is not that big of deal. I used to bottom out once per race without issue when I was racing XC - that was with a 400g, 2.1, semi-slicks on Flows at 22psi (I'm 180#).

    That 2.1 on 23mm inside width Flows set-up were like 2.35 on 30mm inside width rims in regards to tire size to rim inside width ratio. So I already have some experience with this. (That is 2.3:1 and 2:1 tire/rim size respectively, so not exactly, but close enough to realize some benefits.)

    P

  132. #732
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    There's more.
    The added volume gives you more ride compliance front and rear. This makes a hard tail more distance capable. And one with some vertical compliance a short travel fs substitute.
    The sidewall support reduces greatly abrupt washouts, like when you try to recover from a mistake.

  133. #733
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    Quote Originally Posted by PretendGentleman View Post
    I agree with you that the smaller starting volume leads to a more progressive spring rate (but I might be using physics terms incorrectly), but I'm curious if your explanation is the same as mine. I'm not sure if folks are referencing a breakdown in ideal gas laws or just an artifact of the behavior of variables that respond to each other in percentages (in a perfect system, based on P=(nRT)V^-1, if V goes down 2%, P goes up approximately 2%~1-1/(1-.02)). This approximation breaks down for big changes, so a 20% reduction in volume causes about a 25% increase in pressure, .25%=1-1/(1-.2). So one argument, that I would have to think too hard about as someone who does not do much 3d geometry or integrals is the question of whether a wider rim vs a narrow rim experiences a larger percentage reduction in volume when experiencing a load that is just enough to cause a rim strike. I think i know how to prove the answer, but intuitively, i suspect the narrower rimmed wheel experiences a larger percentage reduction in air volume due to a rim strike, thus the spring rate is relatively more progressive than for the wide rim system.
    Yes, PV=nRT applies. Less volume means the pressure goes up more quickly for a given compression. So running over a softball with a 30 PSI tire is going to cause more of a pressure spike with a small volume tire than a large.

    Well keep in mind:
    * the part of a tire that compresses during a hit is a very small percentage of the entire tire. Unlike say a rear shock where 100% of the piston area compresses.
    * So sure the larger volume tire+rim is more linear, but who cares. Likely way smaller than the error in your average bike pump.

    Quote Originally Posted by PretendGentleman View Post
    I am now leaning towards a 40mm rim for my krampus rear wheel. I like that I would buy a bit more flexibility on chainline and running a granny gear for huge climbs. Every mm really does count with this setup.
    I don't see what a wide rim has to do with chainline or granny gears. Wide rims have minimal effect on wheel radius, chain line, or tire width.

  134. #734
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    rim width definitely has an affect on chain line compatibility with wide tires. I ride a krampus and I deal with this regularly as I switch between 1x, 2x, and 3x chainrings for dramatically different terrains/goals.... Mountains vs. plains/party pace vs race pace.

    1mm makes a meaningful difference; you are not wrong to say the effect is minimal, but in this case minimal is significant. now you know what rim width has to do with chainline and granny gears . have you seen the posts all over mtbr of people measuring their tires on different rims with calipers and observing differences and then talking about those differences as if they cared about them....

    And regarding the pv=nrt stuff, I do not understand the comparison with a bike pump, but can imagine you might be saying the error in a bike pump's gauge is bigger than the error you get if you assume changing rim width has no affect on handling/pinching. I would say that spring rates are regressive (exponential coefficient on P or V is less than 1 in absolute value) for wide or narrow rims due to the expansion of the tire.

    I'm not sure how "spring rate" is defined, but pv=nrt is a log linear system, so it might be useful to recognize that P does not respond linearly to V but rather the log of P responds linearly (or nearly so) to changes in the log of V. A physicist could clear this up, I suspect that spring rates are defined such that pv=nrt being log linear means the spring rate is linear (approximately, which of course is the approximation we're implying in this thread should not be made).

    Regarding your other points, small differences are exactly why this thread exists. They do matter, otherwise we wouldn't have dozens and dozens of replies. If the percentage change in volume is small, then we can approximate the response of pressure to volume in constant elasticity terms (1% drop in V causes ~<1% rise in P). The different starting points in the 2 systems and the different changes in volumes for a rim strike means different changes in V. This doesn't mean that a small percentage change in volume makes the discussion of the merits of wide rims in this thread moot. A big percentage change would lead to a larger divergence between the handling characteristics of wide and narrow rims. But we don't need anything to be big to have a useful convesation about it.

    Alltogether rim width has a small effect on pinch flats and handling, and we are internet nerds who spend hours talking about small effects, so when we have a chance to leave our offices to ride our bikes, we are more likely to have a successful experience.

  135. #735
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    Ibis released 41mm rims last year

    Great thread and I went through some of this thread but did anyone notice IBIS's new stance on wider rims?

    "There are exceptions. Downhillers generally use wider rims as they see the benefits of increased control and far superior traction. Wide aluminum rims are heavy though, unacceptably heavy if you ever need to pedal up a hill or accelerate.

    We’re not the first people to discover the wide rim advantages. The early mountain bikers as mentioned above had it right. Back in 2011, Richard Cunningham, the Pinkbike.com tech guru wrote an article called “Wider Rims Are Better” in his Pinkbike Tech Tuesday Series. RC had it right, and we encourage you to read the article. In 2012 Richard wrote about the Syntace W35 MX 35mm wide aluminum rims, once again beating the wide rim drum.

    In 2013 the first wide carbon fiber rims came out, called Derby Rims. Derby is our good friend and in fact Ibis liked his idea so much we funded half the original tooling expense of these rims. Having access to the Derby Rims proved invaluable in testing for our own concepts and designs. Derby’s rims are made in a different factory than ours, as we will be needing a much larger quantity than his source can provide.

    For now, we will only be selling complete wheels, so if you’re looking for rims only, we heartily endorse the product that Derby is selling. If you can get them that is, Derby Rims have been regularly selling out each production run."

    IBIS is now primarily selling wheelsets that have 41mm wide rims. These new rims are coming stock on many of the bikes they sell including the new Mojo HD3. You can check it out on their website.
    I just purchased a set of these rims and will be trying them out probably today if everything goes as planned. Every review I have read so far on the wide rims has been positive many saying it is a game changer using carbon rims has increased the possibility of widening the rims without vastly increasing the weight.

    Also wanted to mention I ride Downhill and Enduro singletrack. I haven't tested the new wheels out but I will report back once I have and take some pictures of my set up. I have been doing a lot of research on this and would not have purchased the new wheels if the evidence wasn't there to suggest this may be a worthwhile upgrade.

  136. #736
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    So...In an attempt to get to the bottom of this, I asked someone who's advice I usually trust, my wife.

    I explained to her that the big discussion always used to be about size, how many inches was best (as in 26" 27.5" 29"). She stopped me cold with a laugh and said it is all personal preference, and that it really doesn't matter at all. Her exact words, " ride what you got and ride it hard".

    She made perfect sense of a long heated discussion, but I had to delve deeper. It was posited to her that possibly width makes a difference. My exact words, "Is wider better".

    Her answer is as follows: " Ohhh definitely!"

    I asked her " is there times when wider is not better?"

    "Well" she says " Not really...but.." she got a little bit sheepish, (why I don't know, but I cant think about that and wheels at the same time) "sometimes, not always, well most times, a little less width is good in the rear, than in the front. So in a perfect world, nice and wide up front, a bit less in the back. But like I said, ride what ya got and ride it hard."

    This all seems too simple, so I asked "what would be considered too wide?"

    She let out a little giggle, and a smile " well if it doesn't fit, then it's a pretty safe bet you bit off more than you can chew."

    I hope some of you have the same closure I now have, thanks to my wonderful wife.

  137. #737
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    So the wife says go wide? That's as good as anything else we've heard here.

  138. #738
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    Quote Originally Posted by sherwin24 View Post
    She stopped me cold with a laugh and said it is all personal preference, and that it really doesn't matter at all. Her exact words, " ride what you got and ride it hard".
    I have the transcript, and that's not really how it went down. This is what she said: She looked down at your waist area, put her hand on your shoulder and said, "honey, the size really doesn't matter. I'll ride what you got and I'll ride it hard". Dude, she's a keeper!

  139. #739
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    Quote Originally Posted by Mountain Cycle Shawn View Post
    I have the transcript, and that's not really how it went down. This is what she said: She looked down at your waist area, put her hand on your shoulder and said, "honey, the size really doesn't matter. I'll ride what you got and I'll ride it hard". Dude, she's a keeper!
    Well I have no clue what you are talking about haha.

    On a side note, my wife just asked me why is wide just now becoming a topic of discussion? I told her it is fairly new and trendy so of course it is getting a lot of airtime.

    "Wow, never new I was such a trendsetter, I went wide 14 years ago, can't believe others are just catching on now" was her reply.

    I knew she rode bikes when I met her 14 years ago, but I never once thought to see what size rims she was riding.

  140. #740
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    Everyone who wants to run 30+mm carbon rims with low pressure on rocky trails needs to buy the WTB Breakout 2.5".
    Keep the Country country.

  141. #741
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    Quote Originally Posted by Mountain Cycle Shawn View Post
    I have the transcript, and that's not really how it went down. This is what she said: She looked down at your waist area, put her hand on your shoulder and said, "honey, the size really doesn't matter. I'll ride what you got and I'll ride it hard". Dude, she's a keeper!
    Quote Originally Posted by sherwin24 View Post
    Well I have no clue what you are talking about haha.

    On a side note, my wife just asked me why is wide just now becoming a topic of discussion? I told her it is fairly new and trendy so of course it is getting a lot of airtime.

    "Wow, never new I was such a trendsetter, I went wide 14 years ago, can't believe others are just catching on now" was her reply.

    I knew she rode bikes when I met her 14 years ago, but I never once thought to see what size rims she was riding.
    Show her the above, she'll explaine it to you.

    On a side note: These new wide rims are like suspension, disc brakes and pretty much every other major improvement in the mountain bike industry. All the trolls come out if the wood work, declaring how they are horrible and it's just a passing fad. Two years from now everyone will be using them, even the trolls and this BS will all be forgotten.

  142. #742
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    Quote Originally Posted by sherwin24 View Post
    Well I have no clue what you are talking about haha.

    On a side note, my wife just asked me why is wide just now becoming a topic of discussion? I told her it is fairly new and trendy so of course it is getting a lot of airtime.

    "Wow, never new I was such a trendsetter, I went wide 14 years ago, can't believe others are just catching on now" was her reply.

    I knew she rode bikes when I met her 14 years ago, but I never once thought to see what size rims she was riding.
    That's because you were only looking at the rims you gave her! Plus, clearly she has not yet met the limit of her width, but is still looking. i'm sure it will all work out in the end. Just not sure which end.....

  143. #743
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    I just ordered the front tire

    Quote Originally Posted by Lelandjt View Post
    Everyone who wants to run 30+mm carbon rims with low pressure on rocky trails needs to buy the WTB Breakout 2.5".
    Have you tried the Breakout 2.5 tires yet? There are two different versions, one for the rear and one for the front. I saw your post and purchased the front tire for my new wheel lol. Going to try it out as I am running 2.4 Ardent/Mking tires right now.

    I just gave my wheels their first test ride and they definitely made a difference. I upgraded though from WTB i23 aluminum rims, so I lost weight and have wider rims also, but the overall ride felt faster. I felt I had more traction and more confidence in general when taking hard lines down the trail. I also had more power going up hill or downhill when pedaling. For some reason going off the little jumps on my trail was easier probably because I lost some weight on the rims but the landing felt better as well. It feels like I have just increased the size of my tires but lost weight off my bike at the same time.

    Kona Process DL 134 w/ Ibis 741 rims 41mm wide
    Attached Thumbnails Attached Thumbnails Wide Rims?  Don't believe the hype...-20150314_124953.jpg  

    Wide Rims?  Don't believe the hype...-20150314_125051.jpg  


  144. #744
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    Gotta say libertybike, thats a sweet looking setup you've got there. I've always liked the new Kona Process and yours looks especially sharp. Custom decals on the rims? The color match is perfect.

    FWIW, I'll be ordering a set of Derby's for my SB66 soon. I get the feeling that in a few years finding a narrow, or non-wide, rim on a new bike is going to be as uncommon as a newly released 26er.
    IBIS Mojo 3
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  145. #745
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    Wow...Great post (lots of interaction which is great!)
    A lot has been said and argued here, some science and some circumstantial, but the bottom line is this: In the early '90's we rode the Red compound RITCHEY v-max 2.35 on our rigid bikes to get more volume (more cushion) and a better contact patch. We dropped the pressure as much as we dared and carried extra tubes for the snake bites that this set-up caused. I switched to IBIS 741 rims on my 2014 Turner Burner (41mm wide) and can't believe how much faster my riding is. What a difference in how much more FUN the rides are with these wide rims at the lower tire pressures though! Amazing! I will never regret the $ I spent and will never go back!
    See you out there y'all!

  146. #746
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    For all those DHers out there: my first DH ride/race of the 2015 season was last weekend in Sequatchie, TN.

    There were no wide carbon rims to be seen. There was a set of previous generation Enves on a carbon V10. The rest of the riders were on aluminum as far as I could see, though I admit I didn't get a peek at the SRAM team bike. The Scott WC DH Team goes for DT Swiss 471 when it is time to go fast. They pick it over the 570 and the Gravity because weight trumps width and they can handle the replacement situation.

    So, from World Cup professional athletes to 40+ weekend warriors to 11 year old shredders...to the bada## dude on the trail bike...we were all riding down some of the steepest, gnarliest tracks we have in the east...without WIDENESS.

  147. #747
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    Quote Originally Posted by sklein View Post
    Wow...Great post (lots of interaction which is great!)
    A lot has been said and argued here, some science and some circumstantial, but the bottom line is this: In the early '90's we rode the Red compound RITCHEY v-max 2.35 on our rigid bikes to get more volume (more cushion) and a better contact patch. We dropped the pressure as much as we dared and carried extra tubes for the snake bites that this set-up caused. I switched to IBIS 741 rims on my 2014 Turner Burner (41mm wide) and can't believe how much faster my riding is. What a difference in how much more FUN the rides are with these wide rims at the lower tire pressures though! Amazing! I will never regret the $ I spent and will never go back!
    See you out there y'all!
    100% true words!!

  148. #748
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    ...and for those grasping for an explanation of the above post: you can't exactly claim DH racing is "conservative" when the entire pro field went to bigger wheels last season, (with questionable results, I might add, since the times overall didn't seem to come down drastically). I'm specifically thinking of Bryceland, who switched from 26" to 27.5"... while leading the WC standings. Graves making the Worlds podium on his retrofitted trail bike the season prior. The Specialized team racing enduro rigs when the course asked for it. Large portions of the field switching to flat pedals for sloppy off-camber courses. These guys aren't luddites. They make changes to their bikes to win races.

    The truth is, gravity racing is a completely different world than what most mountain bikers know. So you slap fatty rims on your bike and suddenly your cornering ability improves by a huge margin-- great. That speaks more about your ability than the rims, because the same effect would not happen for guys who are really fast.
    MUST WATCH: George Brannigan - Loose Laps - Pinkbike
    Last edited by JLF1200; 03-23-2015 at 07:47 PM.

  149. #749
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    Quote Originally Posted by libertybike View Post
    Have you tried the Breakout 2.5 tires yet?
    Nope. I was trying to get my hands on them all last season but a production problem meant there were only a few pairs and Marco got them. He loved them and they worked for him on trails that demanded grip and where rolling speed was critical. He used those tires in every race last year from flow trails to the ProGRT he won. Now that they're finally available I'll be getting a set each of the softs and hards.
    The reason I recommend them for low pressure on wide rims is their nearly DH feeling sidewalls and their width.
    Keep the Country country.

  150. #750
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    Quote Originally Posted by oldranger View Post
    For all those DHers out there: my first DH ride/race of the 2015 season was last weekend in Sequatchie, TN.

    There were no wide carbon rims to be seen. There was a set of previous generation Enves on a carbon V10. The rest of the riders were on aluminum as far as I could see, though I admit I didn't get a peek at the SRAM team bike. The Scott WC DH Team goes for DT Swiss 471 when it is time to go fast. They pick it over the 570 and the Gravity because weight trumps width and they can handle the replacement situation.

    So, from World Cup professional athletes to 40+ weekend warriors to 11 year old shredders...to the bada## dude on the trail bike...we were all riding down some of the steepest, gnarliest tracks we have in the east...without WIDENESS.
    Does your BS ever stop?

  151. #751
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    (in a perfect system, based on P=(nRT)V^-1, if V goes down 2%, P goes up approximately 2%~1-1/(1-.02)). This approximation breaks down for big changes, so a 20% reduction in volume causes about a 25% increase in pressure, .25%=1-1/(1-.2).
    So your math is a bit off. As long as the nRT function stays constant (specifically temp), then the P & V move at a 1to1 ratio in opposite directions. May be easier to think of it as P*V=C so what ever you add to pressure has to be subtracted from Volume or vice versa.

  152. #752
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    Quote Originally Posted by JLF1200 View Post
    ...and for those grasping for an explanation of the above post: you can't exactly claim DH racing is "conservative" when the entire pro field went to bigger wheels last season, (with questionable results, I might add, since the times overall didn't seem to come down drastically). I'm specifically thinking of Bryceland, who switched from 26" to 27.5"... while leading the WC standings. Graves making the Worlds podium on his retrofitted trail bike the season prior. The Specialized team racing enduro rigs when the course asked for it. Large portions of the field switching to flat pedals for sloppy off-camber courses. These guys aren't luddites. They make changes to their bikes to win races.

    The truth is, gravity racing is a completely different world than what most mountain bikers know. So you slap fatty rims on your bike and suddenly your cornering ability improves by a huge margin-- great. That speaks more about your ability than the rims, because the same effect would not happen for guys who are really fast.
    MUST WATCH: George Brannigan - Loose Laps - Pinkbike
    The Motorhead soundtrack in that vid sealed the deal.

  153. #753
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    Quote Originally Posted by oldranger View Post
    For all those DHers out there: my first DH ride/race of the 2015 season was last weekend in Sequatchie, TN.

    There were no wide carbon rims to be seen. There was a set of previous generation Enves on a carbon V10. The rest of the riders were on aluminum as far as I could see, though I admit I didn't get a peek at the SRAM team bike. The Scott WC DH Team goes for DT Swiss 471 when it is time to go fast. They pick it over the 570 and the Gravity because weight trumps width and they can handle the replacement situation.

    So, from World Cup professional athletes to 40+ weekend warriors to 11 year old shredders...to the bada## dude on the trail bike...we were all riding down some of the steepest, gnarliest tracks we have in the east...without WIDENESS.
    If wideness isn't a priority and weight is then why aren't they on 15-17 wide rims? You keep talking about how DH don't want or need wide rims when they were the first to go back to 23-27 wide rims in the first place.

  154. #754
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    Quote Originally Posted by oldranger View Post
    For all those DHers out there: my first DH ride/race of the 2015 season was last weekend in Sequatchie, TN.

    There were no wide carbon rims to be seen. .... So, from World Cup professional athletes to 40+ weekend warriors to 11 year old shredders...to the bada## dude on the trail bike...we were all riding down some of the steepest, gnarliest tracks we have in the east...without WIDENESS.
    Sigh... DH rims have always been the widest rims available - for decades, until the last year or two. Why is that? According to you, just to look pretty (no benefit).

    And here come the wide/tubeless/carbon DH rims you and others can't wrap your head around:

    PIT BITS - Crankworx Rotorua - Prototype Carbon Rim - PIT BITS - Crankworx Rotorua - Mountain Biking Pictures - Vital MTB

    P

  155. #755
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    Quote Originally Posted by Mr.P View Post
    Sigh... DH rims have always been the widest rims available - for decades, until the last year or two. Why is that? According to you, just to look pretty (no benefit).

    And here come the wide/tubeless/carbon DH rims you and others can't wrap your head around:

    PIT BITS - Crankworx Rotorua - Prototype Carbon Rim - PIT BITS - Crankworx Rotorua - Mountain Biking Pictures - Vital MTB

    P
    It's just a matter of time. In a year or two the trolls on this thread will be saving their money for wide rims.

  156. #756
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    Quote Originally Posted by Mountain Cycle Shawn View Post
    It's just a matter of time. In a year or two the trolls on this thread will be saving their money for wide rims.
    Don't be a douche. We get that you love your wide rims, ok?

  157. #757
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    Quote Originally Posted by smilinsteve View Post
    Don't be a douche.
    Next time you're in So. Cal., PM me. I guarantee you wouldn't have the balls to say that to my face!

  158. #758
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    I must be ahead of the times...I switched to skinnier wheels on my trail bike. Velocity P35 to WTB KOM i23.

  159. #759
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    Here is an older, related thread with a little more substantive discussion:

    http://forums.mtbr.com/wheels-tires/...th-756818.html

    Here's some data that agrees with above thread that tire height (therefore circumference) changes very little with rim width:

    29er Tires on Different Rim Width Comparison

    Quote from Craigsj (who has a pretty damn good record of being correct in this forum) in above thread, that pretty much summarizes things about rim width and tire height:

    The irony is that the original purpose of the thread was to show that height is relatively insensitive to rim width which ran contrary to common lore. The claim has been that wider rims support lower pressures and that is, at its most generous, an oversimplification. Tire pressures can't be lowered when rim strikes are a threat. For some people rim strikes are never a threat and those people are, no doubt, connoisseurs of tire performance here.

  160. #760
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    Ladies and Gentleman of the jury, I'm just a Caveman. I fell in some ice and later got thawed out by your scientists. Your world frightens and confuses me. Sometimes the honking horns of your traffic make me want to get out of my BMW and run off into the hills or whatever. Sometimes when I get a message on my fax machine, did little demons get inside and type it? I don't know. My primitive mind can't grasp these concepts.

    So, maybe I'm just simple caveman, but I don't see how wide rims allow lower pressures? Volume is greater, but that would just make the spring rate more linear. It's probably a very small effect, but in any case, I don't see the advantage to this extra volume.

    So if tire height is about the same (less than 1mm difference), then lower pressures will just increase the chance of rim strikes. The rim does nothing to make this less likely.

    So wouldn't it be funny, if people love the extra traction and cornering of their wide rims, only because they are running lower pressures, when those same pressures could also be used on those old fashioned narrow rims? In other words, the rims have nothing to do with it?

    I'm just thinking out loud. Your ways frighten and confuse me. I'm just a simple caveman.
    Last edited by smilinsteve; 03-24-2015 at 01:07 PM.

  161. #761
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    Quote Originally Posted by Mountain Cycle Shawn View Post
    On a side note: These new wide rims are like suspension, disc brakes and pretty much every other major improvement in the mountain bike industry. All the trolls come out if the wood work, declaring how they are horrible and it's just a passing fad. Two years from now everyone will be using them, even the trolls and this BS will all be forgotten.
    I'm glad I have suspension and disc brakes. I don't think 35 mm bar diameters or tapered head tubes, or 11 gears instead of 10, 9 or 8 did a damn thing for me.

    Nothing wrong with questioning the latest fad, especially since there have been some bad ideas in the past. Marketing something new, and making the status quo obsolete or outdated, works. It just works. So that's how we get these improvements. Some good, some not so much.

    The main thing to remember is your bike will ride as good tomorrow as it does today. A new fad doesn't matter to your bike. Bikes and dogs are good that way.

  162. #762
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    Quote Originally Posted by Mountain Cycle Shawn View Post
    Next time you're in So. Cal., PM me. I guarantee you wouldn't have the balls to say that to my face!
    Whether I say it to your face or not has no bearing on whether or not you are a douche, Mr. Internet tough guy.

    Since you call everyone who disagrees with you a troll, don't be so sensitive. If you can dish it out, you can take it.

  163. #763
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    Quote Originally Posted by slowride454 View Post
    I must be ahead of the times...I switched to skinnier wheels on my trail bike. Velocity P35 to WTB KOM i23.
    Kinky. What are your thoughts?

    P

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    Quote Originally Posted by Tenuous View Post
    So your math is a bit off. As long as the nRT function stays constant (specifically temp), then the P & V move at a 1to1 ratio in opposite directions. May be easier to think of it as P*V=C so what ever you add to pressure has to be subtracted from Volume or vice versa.
    That's a negatory there, feller. Try your math: a 20% reduction in P would cause a 20% rise in V to compensate. That's (1-0.2)*P and (1+0.2)*V in mathspeak. What happens to that so-called constant of yours, C?
    C=PV=[(1-0.2)*P] * [(1+0.2)*V]=0.8*1.2*P*V=.96*P*V=.96*C!=C

    A good way to think about the question of the effect of varying rim width for a particular tire is to consider that there is one particular rim width that will maximize the volume of the tire: the max-volume rim width. A narrower rim will shrink the volume until the beads are touching and the tire can be assumed to be a circle with diameter equal to the length of a stretched-flat cross-section of the tire. As the rim gets wider than the max-volume width, the tire is being sretched to the point of losing volume, causing a reduction in the outer diameter of the tire. When the rim width is equal to the cross-sectional length mentioned above, then the volume will drop to zero. This would explain why people have conflicting ideas about whether wider rims lead to taller, shorter, or same height tires. They are considering variations in rim width that span the max-volume rim width and thus find different effects on tire diameter of a change in rim width.
    The max-volume width would have the closest to linear (log-log linear to be precise, due to the nature of PV=nRT) spring rate and all other rim widths would have more progressive spring rates.

    This effect as others have pointed out may be small. The tire physically supporting the rider's load is an important consideration aside from air pressure.

  165. #765
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    Wider tires allow lower pressures.

    Imagine a 1" wide tire @ 30 psi vs a 2.4" wide tire @ 30 psi. The 1" wider tire is going to ride much lower and have a very noticeable flat spot. If you tried to ride a 1" tire @ 30 psi on the trail you'd likely snakebike or damage a rim.

    So clearly 2.4" at 30 psi is much better than 1".

    Similar rules apply when you use a wider rim instead of a wider tire. The same 2.4" tire will have a wider footprint and a higher ride height when used with a wider rim. Sure the footprint will be the same. Lets assume a 200 pound weight (bike + rider) / 30 psi = 6.66" square footprint.

    So with a narrow rim + 2.4 " tire @ 30 psi will have exactly the same size footprint as a wide rim + 2.4" tire @ 30 psi. But the wide rim will result in a wider but shorter footprint.

    The advantages of wider foorprints:
    * higher ride heights
    * higher peak footprint before rim damage.

    Some of course will want to run a lower pressure, which has other advantages:
    * generally better traction
    * better float on soft surfaces like snow or sand

    So yes, you can lower air pressure too much, but generally wider tires (or tire+rim systems) allow for the same protection at lower pressures.

  166. #766
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    Quote Originally Posted by spikebike View Post
    Wider tires allow lower pressures.

    Imagine a 1" wide tire @ 30 psi vs a 2.4" wide tire @ 30 psi. The 1" wider tire is going to ride much lower and have a very noticeable flat spot. If you tried to ride a 1" tire @ 30 psi on the trail you'd likely snakebike or damage a rim.

    So clearly 2.4" at 30 psi is much better than 1".
    Your basic assumption you've made is incorrect . The aspect of the tyre that means you use higher pressure in the small tyre and lower in the larger, is tyre height - ie outside circumference. The 1" tyre is only 1" from dinging the rim (or less). We all know tyres with less size require more pressure, but don't make the assumption at is all a function of width, most is a function of height

  167. #767
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    Quote Originally Posted by spikebike View Post
    Wider tires allow lower pressures.

    Imagine a 1" wide tire @ 30 psi vs a 2.4" wide tire @ 30 psi. The 1" wider tire is going to ride much lower and have a very noticeable flat spot. If you tried to ride a 1" tire @ 30 psi on the trail you'd likely snakebike or damage a rim.

    So clearly 2.4" at 30 psi is much better than 1".

    Similar rules apply when you use a wider rim instead of a wider tire. The same 2.4" tire will have a wider footprint and a higher ride height when used with a wider rim. Sure the footprint will be the same. Lets assume a 200 pound weight (bike + rider) / 30 psi = 6.66" square footprint.

    So with a narrow rim + 2.4 " tire @ 30 psi will have exactly the same size footprint as a wide rim + 2.4" tire @ 30 psi. But the wide rim will result in a wider but shorter footprint.

    The advantages of wider foorprints:
    * higher ride heights
    * higher peak footprint before rim damage.

    Some of course will want to run a lower pressure, which has other advantages:
    * generally better traction
    * better float on soft surfaces like snow or sand

    So yes, you can lower air pressure too much, but generally wider tires (or tire+rim systems) allow for the same protection at lower pressures.
    I think you are generally right, but you are mostly answering an obvious question that is not what this thread is addressing. Yes wider tires have more volume (up to a point), but we are not talking about wider tires, rather we are talking about whether a wider rim has advantages over a narrower rim with the exact same tire.

    Also, your assumptions about PSI assume a perfectly rigid casing. We know that tires balloon as you fill them, so if you start with a certain air pressure and then get on the bike, the change in psi will not be the same for 2 different wheel systems, so the contact patch will have a different area. This affect may be small, but it certainly exists.

    Your summary points are also incorrect. if a 2.4" tire has approximately a 2.4"*pi=7.5" cross sectional length. A 7.5" rim will result in a very wide contact patch, but pinch flats will be a problem and rider height will be lowered.

    This is not a linear system
    Last edited by PretendGentleman; 03-26-2015 at 08:25 AM.

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    Quote Originally Posted by PretendGentleman View Post

    A good way to think about the question of the effect of varying rim width for a particular tire is to consider that there is one particular rim width that will maximize the volume of the tire: the max-volume rim width.
    This.
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    Quote Originally Posted by PretendGentleman View Post
    That's a negatory there, feller. Try your math: a 20% reduction in P would cause a 20% rise in V to compensate. That's (1-0.2)*P and (1+0.2)*V in mathspeak. What happens to that so-called constant of yours, C?
    C=PV=[(1-0.2)*P] * [(1+0.2)*V]=0.8*1.2*P*V=.96*P*V=.96*C!=C
    aching nutsack, sadly you're right. Just sat down and worked out the math.

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    This thread needs a bong hit, too much math!

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    Quote Originally Posted by pharmaboy View Post
    Your basic assumption you've made is incorrect . The aspect of the tyre that means you use higher pressure in the small tyre and lower in the larger, is tyre height - ie outside circumference. The 1" tyre is only 1" from dinging the rim (or less). We all know tyres with less size require more pressure, but don't make the assumption at is all a function of width, most is a function of height
    Ugh.

    Ok, lets assume identical height. Now compare a 2.4" tire to TWO 2.4" tires. For a given load which will ride higher? It's obvious that the dually setup will handle more weight, right? Just like higher end bike cargo trailers or dually pickup trucks.

    Now compare to a 2.4" tire to a 4.8" tire that has identical height (short and fat) and PSI. So they have identical height at zero load. But under say 100 pounds of pressure which will ride higher? The 4.8". Which will handle a higher peak load? The 4.8".

    So which will pinch flat first if you take a big drop onto a flat? 2.4".

    So if using the same tire rom a 23mm rim (like is standard on the nomad) to a 40mm results in:
    * a wider tire
    * a higher volume
    * riding higher
    * higher peak load before a pinch flat (assuming a flat surface)

    Make sense?

  172. #772
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    Quote Originally Posted by PretendGentleman View Post
    Also, your assumptions about PSI assume a perfectly rigid casing. We know that tires balloon as you fill them, so if you start with a certain air pressure and then get on the bike, the change in psi will not be the same for 2 different wheel systems, so the contact patch will have a different area. This affect may be small, but it certainly exists.
    This is not a linear system
    Actually in my experience tires balloon very quickly up to say 15-20 PSI, but very little after. Sure it might not be zero, but I don't see it making nearly the difference that another 20mm of rim adds.

    Agreed that it's not a linear system.

    Quote Originally Posted by PretendGentleman View Post
    Your summary points are also incorrect. if a 2.4" tire has approximately a 2.4"*pi=7.5" cross sectional length. A 7.5" rim will result in a very wide contact patch, but pinch flats will be a problem and rider height will be lowered.

    This is not a linear system
    I don't quite follow your math or reasoning.

    Your tire footprint is a linear system, until the extremes where the rim hits. Weight / pounds_per_square_inch = square_inches of footprint.

    So a 7.5" rim will indeed have a very wide contact patch. Assuming 100 pounds per wheel and 30 psi that would be 3.3 square inches. So something like a 7.5" wide x 0.44 inch contact patch.

    A 2.4" tire would have something like a 2.4" wide x 1.375" contact patch.

    So the longer the contact patch the lower the rim rides... right up till the rim hits.

    Imagine you sitting beside the wheel. The 7.5" rim wheel would look like it's barely touching the ground, less than 0.5" would be in contact with the ground.

    The 2.4" inch would be visibly flattened at the bottom, with almost an inch and a half.

    Now imagine it was 500 pounds per wheel, you need 4x the footprint, the width can't change much, so the length needs to be 4x. The 7.5" rim would be around 2.2", still not very flat. The 2.4" wheel would need be be 7", the rim would be getting noticeably closer to ground.

    So basically the wider tires have a much easier time increasing their footprint because of large hits, thus protecting the rim from hitting the ground. Skinnier tires have to elongate their contact patch, which places the rim closer to the ground.

  173. #773
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    Quote Originally Posted by spikebike View Post
    Ugh.

    Ok, lets assume identical height. Now compare a 2.4" tire to TWO 2.4" tires. For a given load which will ride higher? It's obvious that the dually setup will handle more weight, right? Just like higher end bike cargo trailers or dually pickup trucks.

    Now compare to a 2.4" tire to a 4.8" tire that has identical height (short and fat) and PSI. So they have identical height at zero load. But under say 100 pounds of pressure which will ride higher? The 4.8". Which will handle a higher peak load? The 4.8".

    So which will pinch flat first if you take a big drop onto a flat? 2.4".

    So if using the same tire rom a 23mm rim (like is standard on the nomad) to a 40mm results in:
    * a wider tire
    * a higher volume
    * riding higher
    * higher peak load before a pinch flat (assuming a flat surface)

    Make sense?
    The fact is that rim width does not increase ride height the way you assume.
    I posted examples earlier. How much pressure decrease can you take if the height of the tire is less than 1mm taller?
    Ugh?

  174. #774
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    Quote Originally Posted by smilinsteve View Post
    The fact is that rim width does not increase ride height the way you assume. I posted examples earlier.
    I've read the thread, but I'll have to look for which post you mean. Tire height it set by the manufacturer. The threads in the casing do not stretch significantly, so the TIRE
    height changes minimally with a wider rim.

    But the RIDE height changes directly with width. The wider the footprint the shorter it is. The shorter the footprint the higher the ride height. Did your post discuss tire height? Or ride height?

    Quote Originally Posted by smilinsteve View Post
    How much pressure decrease can you take if the height of the tire is less than 1mm taller?
    Ugh?
    It's quite simple to calculate. What two tire widths did you want to compare? Seems like the common comparisons I see are in the range of 5-10mm wider when going from a 20-25mm wide rim to a 40mm or so wide rim.

  175. #775
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    Quote Originally Posted by spikebike View Post
    Actually in my experience tires balloon very quickly up to say 15-20 PSI, but very little after. Sure it might not be zero, but I don't see it making nearly the difference that another 20mm of rim adds.

    Agreed that it's not a linear system.



    I don't quite follow your math or reasoning.

    Your tire footprint is a linear system, until the extremes where the rim hits. Weight / pounds_per_square_inch = square_inches of footprint.

    So a 7.5" rim will indeed have a very wide contact patch. Assuming 100 pounds per wheel and 30 psi that would be 3.3 square inches. So something like a 7.5" wide x 0.44 inch contact patch.

    A 2.4" tire would have something like a 2.4" wide x 1.375" contact patch.

    So the longer the contact patch the lower the rim rides... right up till the rim hits.

    Imagine you sitting beside the wheel. The 7.5" rim wheel would look like it's barely touching the ground, less than 0.5" would be in contact with the ground.

    The 2.4" inch would be visibly flattened at the bottom, with almost an inch and a half.

    Now imagine it was 500 pounds per wheel, you need 4x the footprint, the width can't change much, so the length needs to be 4x. The 7.5" rim would be around 2.2", still not very flat. The 2.4" wheel would need be be 7", the rim would be getting noticeably closer to ground.

    So basically the wider tires have a much easier time increasing their footprint because of large hits, thus protecting the rim from hitting the ground. Skinnier tires have to elongate their contact patch, which places the rim closer to the ground.
    You missed the point. The 7.5 inch rim means the tire is flat against the ground.

  176. #776
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    Quote Originally Posted by spikebike View Post
    I've read the thread, but I'll have to look for which post you mean. Tire height it set by the manufacturer. The threads in the casing do not stretch significantly, so the TIRE
    height changes minimally with a wider rim.

    But the RIDE height changes directly with width. The wider the footprint the shorter it is. The shorter the footprint the higher the ride height. Did your post discuss tire height? Or ride height?



    It's quite simple to calculate. What two tire widths did you want to compare? Seems like the common comparisons I see are in the range of 5-10mm wider when going from a 20-25mm wide rim to a 40mm or so wide rim.

    Your assumption is that a wider rim results in a wider contact patch. I'm not buying it. A wider rim doesn't make the tire wider.

  177. #777
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    Wide Rims? Don't believe the hype...

    Quote Originally Posted by smilinsteve View Post
    Your assumption is that a wider rim results in a wider contact patch. I'm not buying it. A wider rim doesn't make the tire wider.
    I have a new set of the 'wider' wheels, and yes the tire's contact patch is in fact wider than it was on the narrow hoop. Problem solved, your welcome.


    EBenke

  178. #778
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    Quote Originally Posted by spikebike View Post
    Ugh.

    Ok, lets assume identical height. Now compare a 2.4" tire to TWO 2.4" tires. For a given load which will ride higher? It's obvious that the dually setup will handle more weight, right? Just like higher end bike cargo trailers or dually pickup trucks.

    because you have more area to rest the load on

    Now compare to a 2.4" tire to a 4.8" tire that has identical height (short and fat) and PSI. So they have identical height at zero load. But under say 100 pounds of pressure which will ride higher? The 4.8". Which will handle a higher peak load? The 4.8".

    the contact patch on the 2.4 tyre will be longer and on the 4.8 shorter and wider, but the exact same amount of rubber will be on the road at all identical loads - I'm not convinced there is any difference in height - one is squashed longitudinally and the other laterally

    So which will pinch flat first if you take a big drop onto a flat? 2.4".

    So if using the same tire rom a 23mm rim (like is standard on the nomad) to a 40mm results in:
    * a wider tire
    * a higher volume
    * riding higher
    * higher peak load before a pinch flat (assuming a flat surface)

    Make sense?
    Answers in bold.

    The point is moot anyway, as the tyres we are talking about are not of the same circumference because they are balloons not low profile belted car tyres - so a wider tyre is indeed taller than a narrower tyre

    A rounder fatter contact patch is just a different contact patch but it could be argued that if the strike is say the edge of a gutter perpendicular to the wheel, then there might be more pressure available at that shape of hit versus a point load (sharp rock).

    Fat bike riders seem to use just a little more than 1/2 of what a normal rider uses and their tyres seem to be nearly twice as wide - I've raced 1.9s which need at least 30psi and 2.25s I set to 25 or 26. That seems ballpark to agree with the predicted outcome from the physics and engineers perspective, ie .3/2 is about a 15% height difference - corresponds remarkably close to that psi difference required.

    I'm sure width can play some role, so I shouldn't be absolute, but is suspect you are yay overestimating it in the real Mtb world with round tyres

  179. #779
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    Quote Originally Posted by ebenke View Post
    I have a new set of the 'wider' wheels, and yes the tire's contact patch is in fact wider than it was on the narrow hoop. Problem solved, your welcome.


    EBenke
    Really? How did you measure that?

    I figure that a loaded tire is going to flatten so that the outermost knobs are on the ground. That's the widest it can get, unless you want to start rolling on your side walls.

    The rim width won't effect that. A wide rim can't make the tire wider. It increases the volume and changes the inflated shape, but the contact patch width is fixed by the tread width of the tire.

  180. #780
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    Tire volumn and contact patch is increased with a wider rim. But, the change is so small, it's insignificant and its not what makes wider rims better.

  181. #781
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    Quote Originally Posted by Mountain Cycle Shawn View Post
    Tire volumn and contact patch is increased with a wider rim. But, the change is so small, it's insignificant and its not what makes wider rims better.
    NO you have not read the last 2 pages, clearly. A 7.5" wide rim with a 2.3" tires isn't going to have as much volume as a 2" rim with a 2.3" tire. Unless you are contesting that observation...

  182. #782
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    Quote Originally Posted by PretendGentleman View Post
    NO you have not read the last 2 pages, clearly. A 7.5" wide rim with a 2.3" tires isn't going to have as much volume as a 2" rim with a 2.3" tire. Unless you are contesting that observation...
    Get back to me when you can get a 2.3" tire in a 7.5" rim. Obviously, as with other things in life there is a point where an idea that is blown out of proportion, just doesn't work anymore. What most people are talking about is taking a tire off a narrow rim and putting that same tire on a wider rim. No different tire sizes, or rims that don't exist bull shit. Stop living in a, "Pretend" world.

  183. #783
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    Quote Originally Posted by Mountain Cycle Shawn View Post
    Tire volumn and contact patch is increased with a wider rim. But, the change is so small, it's insignificant and its not what makes wider rims better.
    Heh, have you been convinced Shawn to change your position slightly?

    I might be nitpicking a bit though - size of the contact patch is entirely a question of differing pressure, it's the shape of the contact patch that changes, specifically slightly wider and shorter, but your overall point stands, it's a tiny change and likely not what makes the rim perform differently. (This is without taking into account knobs which will make the question differ depending on the model tyre and pressure that you are measuring at)

    Interesting there is so much discussion on this topic when hardly anyone does anything much more than squeeze their tyres with their thumbs then goes out and rides (1 or 2 psi would make bigger differences than those discussed here - either good or bad)

  184. #784
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    Quote Originally Posted by pharmaboy View Post
    Heh, have you been convinced Shawn to change your position slightly?

    I might be nitpicking a bit though - size of the contact patch is entirely a question of differing pressure, it's the shape of the contact patch that changes, specifically slightly wider and shorter, but your overall point stands, it's a tiny change and likely not what makes the rim perform differently. (This is without taking into account knobs which will make the question differ depending on the model tyre and pressure that you are measuring at)

    Interesting there is so much discussion on this topic when hardly anyone does anything much more than squeeze their tyres with their thumbs then goes out and rides (1 or 2 psi would make bigger differences than those discussed here - either good or bad)
    It depends how you look at it. For me, with the same tire, I'm running a lot lower pressure on the wider rim. So, my volumn has not increased. If you're running the same psi you might get a slight increase. But, not enought to make a difference.

  185. #785
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    Quote Originally Posted by smilinsteve View Post
    You missed the point. The 7.5 inch rim means the tire is flat against the ground.
    Ha, sorry, totally misunderstood you. I thought the non-linear comment was about tire size not increasing linearly with air pressure.

    So yes you can have a rim that's too wide for a tire. But the problems you mention don't happen in normal ranges. The rest of the world (road bikes, motorcycles, cars) uses tires 20-50% wider than the rim. I'd expect the "wider = better" trend to continue from todays common 2-3x (mtb tire vs rim) as wide as a rim down to the 20-50% range.

  186. #786
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    Quote Originally Posted by smilinsteve View Post
    Your assumption is that a wider rim results in a wider contact patch. I'm not buying it. A wider rim doesn't make the tire wider.
    Actually that's exactly what it does. It does not however make the tire taller.

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    Quote Originally Posted by smilinsteve View Post
    Really? How did you measure that?

    I figure that a loaded tire is going to flatten so that the outermost knobs are on the ground. That's the widest it can get, unless you want to start rolling on your side walls.
    I agree that the optimal knobby pattern will change for say a 20mm rim vs a 40mm rim. But the accounts I've heard claim 5-10mm wider tire when upgrading to a wider rim. Say you buy a 2.4" tire that's approximately 2.4" wide when mounted on a 20-25mm rim. If it's more like 2.6" when mounted on a 40mm rim that's not that big a difference.

    Quote Originally Posted by smilinsteve View Post
    The rim width won't effect that. A wide rim can't make the tire wider. It increases the volume and changes the inflated shape, but the contact patch width is fixed by the tread width of the tire.
    Pictures I've seen with people measuring with calibers show that in fact the tire is wider.

    Tire width does have a maximum, but if you are trying to exceed that you are under inflated. I'd expect wider rims to have a squarer footprint that's shorter and wider than a skinny rim. Even if it's the same at maximum widgth I'd expect the skinnier rim to taper more quickly.

  188. #788
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    The wider contact patch comes from the fact that most people with wider rims run lower pressure. Most tires don't get measurableably wider. But the edge knobs stand up higher and the top of the tire wants to flatten out. The tire does not get any taller.

  189. #789
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    Quote Originally Posted by spikebike View Post
    I agree that the optimal knobby pattern will change for say a 20mm rim vs a 40mm rim. But the accounts I've heard claim 5-10mm wider tire when upgrading to a wider rim. Say you buy a 2.4" tire that's approximately 2.4" wide when mounted on a 20-25mm rim. If it's more like 2.6" when mounted on a 40mm rim that's not that big a difference.



    Pictures I've seen with people measuring with calibers show that in fact the tire is wider.

    Tire width does have a maximum, but if you are trying to exceed that you are under inflated. I'd expect wider rims to have a squarer footprint that's shorter and wider than a skinny rim. Even if it's the same at maximum widgth I'd expect the skinnier rim to taper more quickly.
    1st para - read this

    29er Tires on Different Rim Width Comparison

    25 to 35mm increases width by approximately 1mm , so a 2.4 tyre changes to around a 2.42 tyre or something (can't be arsed to do the maths right now, but it's buggar all)

    The main thread on this subject that has heaps of properly technical answers, and also makes sure people understand that belted car and motorbike tyres are totally different animals is referenced every couple of pages here, and really needs to be read by all

  190. #790
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    Quote Originally Posted by smilinsteve View Post
    Really? How did you measure that?

    I figure that a loaded tire is going to flatten so that the outermost knobs are on the ground. That's the widest it can get, unless you want to start rolling on your side walls.

    The rim width won't effect that. A wide rim can't make the tire wider. It increases the volume and changes the inflated shape, but the contact patch width is fixed by the tread width of the tire.
    I didn't say the tire got wider. I said the contact patch got wider. The wider wheel actually widens the contact patch. The contact patch is not fixed by the width of the tire.


    EBenke

  191. #791
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    Is there really anyone out there breaking out calipers and dyes to measure and compare different contact patches between various tire/rim width combinations?

  192. #792
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    Quote Originally Posted by ebenke View Post
    I didn't say the tire got wider. I said the contact patch got wider. The wider wheel actually widens the contact patch. The contact patch is not fixed by the width of the tire.


    EBenke
    Finally someone with some common sense!

  193. #793
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    Inflation pressure helps determine contact patch at any point of a tire's interaction with the trail surface-- climbing at slow speed, or hitting a rock, or landing a jump.
    You set the pressure to avoid rim hits at the most tire challenging point for a ride so you can make it through without damage.
    Wide rims increase volume. You need less pressure to avoid the rim hit point.
    The tire can deform more before it reaches that point. From that added deformation relative to the same tire on a skinny rim at the same point along the trail comes a larger contact patch and more performance.
    Tire rollover is more dramatic. A wide rim gives the sidewall support it just doesn't get at all with a skinny rim. Instead you can get abrupt tire rollover with a sudden loss of traction that can put you on the ground. When you don't have to deal with that it's possible to recover within the time you get as traction is lost more gradually from a higher rollover threshold.

  194. #794
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    Quote Originally Posted by Mountain Cycle Shawn View Post
    It depends how you look at it. For me, with the same tire, I'm running a lot lower pressure on the wider rim. So, my volumn has not increased. If you're running the same psi you might get a slight increase. But, not enought to make a difference.
    In other words, its lower pressure you like, not wide rims.

  195. #795
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    Quote Originally Posted by J.B. Weld View Post
    Is there really anyone out there breaking out calipers and dyes to measure and compare different contact patches between various tire/rim width combinations?
    No, but there are people out there pretending they know the length and width of their contact patches.

  196. #796
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    Quote Originally Posted by ebenke View Post
    I didn't say the tire got wider. I said the contact patch got wider. The wider wheel actually widens the contact patch. The contact patch is not fixed by the width of the tire.


    EBenke
    Explain how the contact patch can be wider than the measurement of the total tread rubber width from outside lug to outside lug. Thanks.

  197. #797
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    Quote Originally Posted by eb1888 View Post
    Inflation pressure helps determine contact patch at any point of a tire's interaction with the trail surface-- climbing at slow speed, or hitting a rock, or landing a jump.
    You set the pressure to avoid rim hits at the most tire challenging point for a ride so you can make it through without damage.
    Right so far, but..

    Wide rims increase volume. You need less pressure to avoid the rim hit point.
    The tire can deform more before it reaches that point. From that added deformation relative to the same tire on a skinny rim at the same point along the trail comes a larger contact patch and more performance.
    Wide rims do increase volume, but they do not significantly increase tire height, and more volume does nothing to improve resistance to pinch flats assuming equal pressure. And I do not know what you are getting at with your "added deformation" concept.

    Tire rollover is more dramatic. A wide rim gives the sidewall support it just doesn't get at all with a skinny rim. Instead you can get abrupt tire rollover with a sudden loss of traction that can put you on the ground. When you don't have to deal with that it's possible to recover within the time you get as traction is lost more gradually from a higher rollover threshold.
    I'm still thinking about this idea, but most models I have seen on the subject give little or no credit to the tire structure for the support the tire gives. It all comes from the air pressure, and therefore moving out the sidewall does not matter.

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    Quote Originally Posted by Mountain Cycle Shawn View Post
    The wider contact patch comes from the fact that most people with wider rims run lower pressure. Most tires don't get measurableably wider. But the edge knobs stand up higher and the top of the tire wants to flatten out. The tire does not get any taller.
    Regardless of rim size, the "top of the tire wants to flatten out".
    Any mountain bike tire on any width rim is flattening across its total tread width unless it is pumped up so much that it can't, which more of a road tire scenario.

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    Quote Originally Posted by smilinsteve View Post
    most models I have seen on the subject give little or no credit to the tire structure for the support the tire gives. It all comes from the air pressure, and therefore moving out the sidewall does not matter.
    Maybe by visualizing the shape of the tire on two different width rims it can be easier to think about how a wider rim will allow the sidewall to help make the tire more difficult to wiggle side to side. More force would be needed the wider the tire beads were separated until you wouldn't be able to push the tire at the tread side to side at all. Whereas when the two beads are brought together and touch you can easily move it back and forth. That difference in washout threshold is significant when I'm riding.

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    Quote Originally Posted by spikebike View Post
    I agree that the optimal knobby pattern will change for say a 20mm rim vs a 40mm rim. But the accounts I've heard claim 5-10mm wider tire when upgrading to a wider rim. Say you buy a 2.4" tire that's approximately 2.4" wide when mounted on a 20-25mm rim. If it's more like 2.6" when mounted on a 40mm rim that's not that big a difference.



    Pictures I've seen with people measuring with calibers show that in fact the tire is wider.

    Tire width does have a maximum, but if you are trying to exceed that you are under inflated. I'd expect wider rims to have a squarer footprint that's shorter and wider than a skinny rim. Even if it's the same at maximum widgth I'd expect the skinnier rim to taper more quickly.
    I think the wider caliper measurements you have seen are are max width of the sidewall bulge, not tread width, and definitely not contact patch width.

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