Wide rims: The best thing to ever happen to a slacked out bike.- Mtbr.com
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  1. #1
    bpuodt
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    Wide rims: The best thing to ever happen to a slacked out bike.

    I see a lot of people using excellent tires with poor results. One of the best cornering tires I have ever been on is the Kenda Nevegal 2.5 DH. A freind of mine uses the same tire but on skinny rims and curses the thing to all hell because it washes out in corners. I keep telling him to get a much wider rim and the tire would hook up.

    Unless you also increase rim width, you will only hurt your turning ability with increasing just tire size. This really holds true for riders who ride choppered out long travel bikes with the center of gravity more in the rear. Unless you have good traction up front you will wash out in corners bad due to not as much weight over the front wheel and the slack head angle. To make up for this we must use stickier, larger, heavier tires up front to get back our cornering. XC guys don't need to worry about rim width as much because they tend to have more weight over the front wheel and steeper head angle.

    As a rule of thumb for bikes with a head angle of less than 69 deg you should maintain a minimun rim width for the tire size. This varies slightly front tire to tire, but for the most part holds true for DH tires.

    Tires 2.3 and under - min 30-34mm rim width
    Tires above 2.3 to 2.5 - min 36-40mm rim width
    Tires above 2.5 to 3.0 - min 43-46mm rim width

    If you experience a lack of control in corners, it may be due to a skinny rim, not the tire type.

    Hope this helps rail some freakin corners!! Get riding!

  2. #2
    bpuodt
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    Am I correct in my sizing chart? Any corrections?


    Why does a wider rim make a tire turn better?

    It squares out the tread profile so that the side knobs are more level with the center knobs. When you corner the side knobs will dig in sooner without having to lean the bike way over. The wider rim also adds support to the sides of the tire and helps prevent it from mushing around on the rim under high loads.

  3. #3
    Elitest thrill junkie
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    I hate really wide rims because the spokes run down the middle, and the edge of the rim is unsupported and easily dented. It depends on the profile, some "wide" rims over the years have had big "V" sections and were adaquate, some like double wides are terrible and crazy-weak for the reason I mentioned.

  4. #4
    bpuodt
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    Quote Originally Posted by Jayem
    I hate really wide rims because the spokes run down the middle, and the edge of the rim is unsupported and easily dented. It depends on the profile, some "wide" rims over the years have had big "V" sections and were adaquate, some like double wides are terrible and crazy-weak for the reason I mentioned.
    Depends on the rim like you said. Flat rims are crappy, period.

    Pyramid shaped ones are way stronger esp. the Mag 30 rim. Mine is the 39mm Mag 30 and I've bottomed the sucker out on countless rocks and roots at 14 psi. Still within a 1/32 of trueness with no flatspots or sidwall dents.

    Rim strength also has a lot to do with how well the wheel was built. I have all of my custom wheels built by one of Lance Armstrong's former wheel builders. A custom wheel build doesn't get any better than that. Even though I pay $70 in labor a wheel, I know I'm getting the best in the world (he does free trueing and tensioning). I went with a Zoke 20mm hub (the strongest) 2.7mm gauge spokes and the Mag 30 rim. It's nearly impossible to get a front wheel as strong and stiff as that.


    Yeah, avoid wide flat rims. Pyramid ones are the ticket.

    --------------------------------------------

    Speaking of tire variances. The Nokian Gazzalodi Core 2.3 tire I use is naturally a very square profile tire. It works great on even 29mm wide rims all the way up to 34 mm rims (for super slacked out bikes). Other 2.3 tires like the Maxxis High roller DH and Minion DH need a much wider rim of 34mm to get the same cornering effect. In fact putting the Nokian on the 34 mm rim is almost too much turning for most cases, b ut it feels perfect in off camber loose over hard conditions.

  5. #5
    not so super...
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    Tires 2.3 and under - min 30-34mm rim width
    Tires above 2.3 to 2.5 - min 36-40mm rim width
    Tires above 2.5 to 3.0 - min 43-46mm rim width
    Where did this data come from?? Does this "rule of thimb" apply only to recreational riders or should someone run out and tell all the Pros too? I'm sure they'd be interested in this new information.

    My build is completely f'd according to your data and I thought I finially got it dialed. Damn!

    68.5 degree headangle
    2.5" tires
    28mm rim
    Nothing to see here.

  6. #6
    bpuodt
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    Quote Originally Posted by SSINGA
    Where did this data come from?? Does this "rule of thimb" apply only to recreational riders or should someone run out and tell all the Pros too? I'm sure they'd be interested in this new information.

    My build is completely f'd according to your data and I thought I finially got it dialed. Damn!

    68.5 degree headangle
    2.5" tires
    28mm rim

    None of it is "new" info.

    There's a lot to consider besides tire choice and rim width. There's also the fact that we all ride different terrain. If you ride mostly hardpack then a slightly narower rim will be good. If you ride loose and loose over hard like most of us then it's better to get a wider rim.


    Downsides to wider rims?

    Sometimes not as strong (easily avoided)
    More rolling resistance (more tread touching ground = slower in straight line)


    I suggest trying a 2.3 tire on your 28mm rim for the heck of it. You might like the results. I've never ridden a single 2.5 tire on a 28mm rim that didn't lack cornering control to a degree.



    Remember this rule of thumb also becomes more true with the slacker the head angle. Being close to 69 is not going to have the same effect as a 66 deg HA.

  7. #7
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    Sorry but your info is a bit off. 45mm? Gonna race the Iditabike or something?

    I run 2.7's on 30mm rims, and really wouldn't want anything wider.

  8. #8
    bpuodt
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    Quote Originally Posted by singletrack
    Sorry but your info is a bit off. 45mm? Gonna race the Iditabike or something?

    I run 2.7's on 30mm rims, and really wouldn't want anything wider.
    Like I said, it also depends on terrain and how fast you want to go in a straight line.

    Racers might not like wider rims due to the added rolling resistance, which makes sense.

    If your goal is to maximize turning ability, then you must sacrifice some speed.



    Have you tried using a wider rim or a narrower tire? I guarantee you won't be liking 30mm x 2.7 once you try a 40-45mm x 2.7.




    Another note on rims and tires. Having a large tire on a small rim will only be halfway good. You either have to pump it way up to prevent wiggling on the rim (which destroys traction) or you have to leave it soft and mushy on the rim (which destroys cornering stability).

    A wide rim with wide tire gives the best of both worlds. You can pump it up enough for excellent stability, but at the same time have it remain soft for traction.


    It's true, people really do think they have it great until they experience "better." I was just like you running a 2.6 on a 27mm rim for a year straight before realizing how much cornering I was losing with the small rim. I can now go into any corner and rail it without any braking or worry of the front tire washing out.

  9. #9
    TNC
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    No blanket solution.

    Quote Originally Posted by Robot Chicken
    I see a lot of people using excellent tires with poor results. One of the best cornering tires I have ever been on is the Kenda Nevegal 2.5 DH. A freind of mine uses the same tire but on skinny rims and curses the thing to all hell because it washes out in corners. I keep telling him to get a much wider rim and the tire would hook up.

    Unless you also increase rim width, you will only hurt your turning ability with increasing just tire size. This really holds true for riders who ride choppered out long travel bikes with the center of gravity more in the rear. Unless you have good traction up front you will wash out in corners bad due to not as much weight over the front wheel and the slack head angle. To make up for this we must use stickier, larger, heavier tires up front to get back our cornering. XC guys don't need to worry about rim width as much because they tend to have more weight over the front wheel and steeper head angle.

    As a rule of thumb for bikes with a head angle of less than 69 deg you should maintain a minimun rim width for the tire size. This varies slightly front tire to tire, but for the most part holds true for DH tires.

    Tires 2.3 and under - min 30-34mm rim width
    Tires above 2.3 to 2.5 - min 36-40mm rim width
    Tires above 2.5 to 3.0 - min 43-46mm rim width

    If you experience a lack of control in corners, it may be due to a skinny rim, not the tire type.

    Hope this helps rail some freakin corners!! Get riding!
    Really you make some good points here about tire/rim issues, though I don't think I go along with the 40+ rim size recommendation as any kind of a rule. A lot will also depend on the specific tire design and its profile. As long travel, big hit, trail bikes have become more common, there are more relatively large tires that are available that seem to work quite well with more conventionally sized rims. Though some of this can't be determined without actually seeing the tire mounted and aired up, there might be a rule of thumb that most tires with a 55mm or greater width rating shouldn't be mounted on the more conventional 22-24mm width rims for optimum performance. I'd rather use the metric rating system, like 58X559 for example, than using the 2.3, 2.5, etc. system. There seems to be a little more credibility in the accuracy of the metric system IMO as compared to the actual size of the tire. I don't quite know why this seems to be the case.

    You make a good general observation about the benefit of wider rims, even just for DH, but like most things, circumstances change that require tweaking of the tire type, design, shape, etc. and how these tires fit certain rim sizes. The type of course obviously may require a more rounded profile of a given tire to perform optimally, and so a slightly narrower rim may be the answer. Lots of variables to consider. The best thing you've pointed out here is the oft overlooked fact that many riders don't put much thought in rim sizes when picking their tires for their needs.

  10. #10
    10001110101
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    Quote Originally Posted by Robot Chicken
    I see a lot of people using excellent tires with poor results. One of the best cornering tires I have ever been on is the Kenda Nevegal 2.5 DH. A freind of mine uses the same tire but on skinny rims and curses the thing to all hell because it washes out in corners. I keep telling him to get a much wider rim and the tire would hook up.

    Unless you also increase rim width, you will only hurt your turning ability with increasing just tire size. This really holds true for riders who ride choppered out long travel bikes with the center of gravity more in the rear. Unless you have good traction up front you will wash out in corners bad due to not as much weight over the front wheel and the slack head angle. To make up for this we must use stickier, larger, heavier tires up front to get back our cornering. XC guys don't need to worry about rim width as much because they tend to have more weight over the front wheel and steeper head angle.

    As a rule of thumb for bikes with a head angle of less than 69 deg you should maintain a minimun rim width for the tire size. This varies slightly front tire to tire, but for the most part holds true for DH tires.

    Tires 2.3 and under - min 30-34mm rim width
    Tires above 2.3 to 2.5 - min 36-40mm rim width
    Tires above 2.5 to 3.0 - min 43-46mm rim width

    If you experience a lack of control in corners, it may be due to a skinny rim, not the tire type.

    Hope this helps rail some freakin corners!! Get riding!
    So by this logic I should only run a 2.0 max on my Mavic 321s?

  11. #11
    Glad to Be Alive
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    Quote Originally Posted by marsb
    So by this logic I should only run a 2.0 max on my Mavic 321s?
    yeah...if you want the best results.....I personally don't like the added weight of a wider rim....in fact when I race I go from the huge 2.8 Michelins down to the small 2.5 Highrollers...for less traction but better pedaling
    the trick is ENJOYING YOUR LIFE EACH DAY, don't waste them away wishing for better days

  12. #12
    Justin Vander Pol
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    Your rim width numbers are definitely off, but you make a good point about wider rims. Fatty tires on a skinny rim will fold over and wobble around while cornering.

    Mavic's new rim naming scheme includes width, but its the inside width of the rim wall (the part the bead seats against) instead of the outside of the rim. The first number is "quality" 7 is top of the line tubed, 8 is top of the line tubeless. The last 2 numbers are rim width. So a 729 is their best tubed rim in a 29 mm width.

    Mavic's biggest rim is the EX729 (formerly D321). 29mm, and this a nice wide rim. There are definitely wider rims out there, but most racers or freeriders won't need anything bigger than this, even with the huge Kenda Nevegal 2.7's.

    Mavic's "downhill" (really a nice trailbike rim, or rim for DH racers who get free parts) tubeless is the EX823. This rim is 23mm.

  13. #13
    10001110101
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    Quote Originally Posted by juice
    Your rim width numbers are definitely off, but you make a good point about wider rims. Fatty tires on a skinny rim will fold over and wobble around while cornering.

    Mavic's new rim naming scheme includes width, but its the inside width of the rim wall (the part the bead seats against) instead of the outside of the rim. The first number is "quality" 7 is top of the line tubed, 8 is top of the line tubeless. The last 2 numbers are rim width. So a 729 is their best tubed rim in a 29 mm width.

    Mavic's biggest rim is the EX729 (formerly D321). 29mm, and this a nice wide rim. There are definitely wider rims out there, but most racers or freeriders won't need anything bigger than this, even with the huge Kenda Nevegal 2.7's.

    Mavic's "downhill" (really a nice trailbike rim, or rim for DH racers who get free parts) tubeless is the EX823. This rim is 23mm.
    Thank you. I thought his numbers sounded fishy. If his statement were true, then no Mavic rims would be compatible w/ anything larger than a 2.3 ('cept maybe Deemax?)

  14. #14
    bpuodt
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    Quote Originally Posted by marsb
    Thank you. I thought his numbers sounded fishy. If his statement were true, then no Mavic rims would be compatible w/ anything larger than a 2.3 ('cept maybe Deemax?)
    He's talking about iinside width, im talking about outside width. Big difference. Of up to 6mm.

  15. #15
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    Cant be bothered to go and check the sizes but I am running maxxix high rollers 2.5 on mavic 719. Hane run them on 729 and found that the cornering not as good. I put this down to the tire profile being too square. With the rounder profile more of the tread is in contact with the ground giving more grip.......at least thats what I reckon.
    "for a hill they would kill why, they do not know"

  16. #16
    t66
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    Right On

    Obvious just by looking at how a big tire sits on narrow rim. Hard to quantify differences, some tires will be less affected but it's a factor of the sidewall stiffness, terrain, air pressure and to some extent tread pattern and profile... My 2.5's fit and perform great on 36mm rims even on my trailbike w/68 degree HA. I briefly ran some 28mm "Single Tracs" and overall, big tires didn't perform as well.

  17. #17
    Soul Cycles
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    i run 2.4's on my new double wides...
    SELLING-

    Manitou Stance Statioc

    Huricane FORK UP

    Tioga XC Rims Still in wrap

  18. #18
    bpuodt
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    Quote Originally Posted by sreiman
    i run 2.4's on my new double wides...
    and.... how does it do? That's a pretty wide rim for such a tire.

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