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  1. #1
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    Tire pressure for all around XC riding?

    I was curious to know what tire pressure is the best for all around xc use?
    I had IRC Mythos on my K2 and ran them very high because someone told me that I would get pinch flats left and right if I didn't.
    I now have Kenda Nevegals on my Cannondale Rush and was curious where people tend to have their pressure set. I normally ride pretty rocky/root filled technical terrain, with a little mud thrown in once in a while and some nice long downhills.
    Any suggestions would be great. Thanks

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    i run 40psi on 2.00 tires on my rigid
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    As low as possible. I'd start at the lowest recommended pressure (as printed on the tire) and see if you get a pinch flat (small holes on both sides of tube where it contacts the rim). If so, put in a few more psi and run that. If you don't get a pinch flat, run a few psi lower until you do pinch flat.

    Tire pressure is an individual thing. You may also play with the pressure to see how it effects handling, traction, and rolling-resistence.

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    How much do you weigh? A 140 lb. rider can get away with much lower psi than a 210 lb. rider .

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    Quote Originally Posted by Lugi
    I was curious to know what tire pressure is the best for all around xc use?
    I had IRC Mythos on my K2 and ran them very high because someone told me that I would get pinch flats left and right if I didn't.
    I now have Kenda Nevegals on my Cannondale Rush and was curious where people tend to have their pressure set. I normally ride pretty rocky/root filled technical terrain, with a little mud thrown in once in a while and some nice long downhills.
    Any suggestions would be great. Thanks
    You have to experiment. Keep dropping the pressure until you start getting pinch flats or the tires feel squirmy in the corners, then add 2-3 psi. This will be where most tires will preform the best, though a few models may have a sweet spot that is a little higher depending on riding style and terrain.
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    I'm a big fan of lower pressures. I generally run about 22-23 on my 2.3-2.4 tires, 24-25 on 2.1's. I weigh 160 and ride rocky and rooty trails, but the rocks around here tend to not have sharp edges. I will add a couple psi if I expect to be riding somewhere with sharper rocks. My trails also tend to be a lot of slow technical riding, so the low pressure really pays off. If I expect to ride somewhere with higher speed turns, I will up the pressure a little to avoid that squirmy feeling Shiggy mentioned (it can be real unnerving). I am running tubes (not tubeless).

    Also be aware that I have yet to find 2 tire pressure gauges that give the same reading, so my psi listings are relative to my main tire gauge.
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    Quote Originally Posted by trailville
    I'm a big fan of lower pressures. I generally run about 22-23 on my 2.3-2.4 tires, 24-25 on 2.1's. I weigh 160 and ride rocky and rooty trails, but the rocks around here tend to not have sharp edges. I will add a couple psi if I expect to be riding somewhere with sharper rocks. My trails also tend to be a lot of slow technical riding, so the low pressure really pays off. If I expect to ride somewhere with higher speed turns, I will up the pressure a little to avoid that squirmy feeling Shiggy mentioned (it can be real unnerving). I am running tubes (not tubeless).

    Also be aware that I have yet to find 2 tire pressure gauges that give the same reading, so my psi listings are relative to my main tire gauge.
    22psi? isnt that kinda low? whats your tire look like while riding.
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    Quote Originally Posted by Spawne32
    22psi? isnt that kinda low? whats your tire look like while riding.
    Evidently, not for him. I rarely have more than 30psi (usually less) in any of my tires and I outweigh trailville by at least 20 pounds.

    I do not look at my tires while riding.
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    Quote Originally Posted by shiggy
    Evidently, not for him. I rarely have more than 30psi (usually less) in any of my tires and I outweigh trailville by at least 20 pounds.

    I do not look at my tires while riding.
    i mean like when weight is on it, i would figure 20psi on that size tire would be almost flat
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  10. #10
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    Drop psi until you get pinch flats. Every one and every ride is different. If you ride slow and/or easy, you can get away with very low pressures. However, I'm only 140lbs, but can't drop the rear below 35 psi or I will pinch flat when pounding over rough trails.

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    i am always somewhat confused about what pressures to run for trail riding, but what seems to "feel" best to me (i weight about 170lbs with gear) is 28 psi front, and 36 psi rear on maxxis high roller 2.35 single ply's, give or take a very few psi. any more on the front and it feels sketchy, less and i feel the rim getting tagged on bigger rocks. on the rear, less than 36 and it feels like the bike won't roll fast enough (and rim gets tagged), more and i can feel the back skipping over too much stuff, braking is bad, and too much boot-boot. i tend to try to run as much pressure as i can get away with though, because i have more fun riding when the bike rolls faster - this is for general trail riding. but for bike parks i run 2.5 maxxis 2-ply dh tires with 27 psi front, and 35 rear, exactly. for dirt jumps i run 40 psi front, and 50 psi rear for railing berms at high g's - although this can vary more since you don't have to deal with terrain on flow trails.

    why more in back than front? because i DO look at my tires while i ride! one of the things i do when testing a different tire pressure is do a "tire sag" check - i sit on the bike and look at the tire to see how much it bulges at a certain psi. i can't explain here how to judge this, but keep in mind that a tire works best on a certain size of contact patch that will vary with psi, tread design, rider weight, casing design, tire size, rider weight distribution, riding style, dynamic forces while riding, and other factors. as part of my riding style, i try to keep the front end light as often as i can by keeping my weight on the pedals (not on my hands), and when riding faster and more aggressive (which i do as often as possible) the weight distribution shifts more rearward. add to this that the weight distribution on my bike is already 40/60 front-to-rear. so, the weight distribution calls for more pressure in the rear and less in the front to keep things balanced-out.
    Last edited by mr.niles; 10-06-2009 at 10:58 PM.

  12. #12
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    I'm 143lbs, riding 24f/28r on 26x2.0" at the moment.

    The rear is a bit skinny for a 2.0; when I get a true 2.0, I'll drop the pressure to 26ish.

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    Quote Originally Posted by mr.niles
    i am always somewhat confused about what pressures to run for trail riding, but what seems to "feel" best to me (i weight about 170lbs with gear) is 28 psi front, and 36 psi rear on maxxis high roller 2.35 single ply's, give or take a very few psi. any more on the front and it feels sketchy, less and i feel the rim getting tagged on bigger rocks. on the rear, less than 36 and it feels like the bike won't roll fast enough (and rim gets tagged), more and i can feel the back skipping over too much stuff, braking is bad, and too much boot-boot. i tend to try to run as much pressure as i can get away with though, because i have more fun riding when the bike rolls faster - this is for general trail riding. but for bike parks i run 2.5 maxxis 2-ply dh tires with 27 psi front, and 35 rear, exactly. for dirt jumps i run 40 psi front, and 50 psi rear for railing berms at high g's.
    Some time you should actually put a clock (or GPS) on your runs and see how different pressures affect your speeds.

    I have done this with a Garmin Edge GPS when testing tires. The runs that felt the fastest were many times the slowest. They where exciting and it seemed I was going into the corners at a higher speed but in reality the tires where just bouncing and sliding more and harder to control. Slower into the turn and slower yet coming out of them. Heck, the higher pressure runs where even slower on the climbs.

    That is not to say the faster, low pressure runs were more fun. There was a lot less drama in covering the lap. Definitely not as thrilling a ride.
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  14. #14
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    Quote Originally Posted by Spawne32
    i mean like when weight is on it, i would figure 20psi on that size tire would be almost flat
    The point is if you are not bottoming out the tire, it does not matter. 22psi in 2.3-2.4" tires is not unusual or "look" low (if you could see it).
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    well im about 165 pounds and 40 psi in the rear is usually where i feel comfortable, adding a bit more flex to the front tire might make it a little easier on my arms but i dont know how much more difficult it would be to accel the bike forward with lower tire pressure. I might play around with it a little more now that i got my CST copperheads mounted today.
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    Quote Originally Posted by shiggy
    Some time you should actually put a clock (or GPS) on your runs and see how different pressures affect your speeds.

    I have done this with a Garmin Edge GPS when testing tires. The runs that felt the fastest were many times the slowest. They where exciting and it seemed I was going into the corners at a higher speed but in reality the tires where just bouncing and sliding more and harder to control. Slower into the turn and slower yet coming out of them. Heck, the higher pressure runs where even slower on the climbs.

    That is not to say the faster, low pressure runs were more fun. There was a lot less drama in covering the lap. Definitely not as thrilling a ride.
    in fact i do have timing device coming in the mail! yeah, it's hard to tell! that's why it's confusing to me. i'm always changing my presuures around to try and figure out what is best. i will try lower pressures, but i'm just not sure where to start. any ideas?

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    Over 190 with water and gear, 30 in the front and 32 in the rear with small 2.4's. These tires are definitively faster at 30-32 than they are at 40 or more whether I am on the road or the trail. I wouldn't have believed it if I had been told beforehand. I tried 28 in the front and 30 in the rear but felt the rim hit on both ends during that ride.

  18. #18
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    Quote Originally Posted by Spawne32
    22psi? isnt that kinda low? whats your tire look like while riding.
    It's fine. Remember, that pressure is in a wider 2.3-2.4 tire. Once you feel how your tires can conform to rocks and roots rather than bouncing off of them, you will appreciate lower pressures. To be honest, I've never had issues with pinch flatting. I think part of it is due to the the mainly rounded rocks we have around here (thanks glaciers), and part is due to the fact that I started mtn biking on rigid bikes and even though I run suspension now (front and full), I still unweight the bike as I go over and through stuff.

    I've played with all kinds of pressures over the years. In the early 90s I started running between 30 and 35 psi because I was new to MTB and the people that knew what they were talking about recommended lower pressures (that seemed low to me at the time). Later on I got sucked into the "higher pressure is faster" thinking and started running 40 - 45. I also remember that some tires during the mid 90s started coming with separate pressure recommendations if you were riding suspension versus rigid (min pressure on suspension was like 5 or 10 psi higher), so since I was running front suspension then (if you can call a 63mm Judy suspension), I went with the recommendations.

    Eventually (years later) I got sick of bouncing and glancing sideways off of every rock and root on the trail and started lowering my pressures again. Then in more recent years I discovered wider 2.3 - 2.4 XC tires (I had been running 1.95s to 2.1s up to that point) and even lower pressures, and a whole new world opened up to me. I was more than happy to trade some speed for better traction and control, but then I started reading in these forums that I probably wasn't sacrificing speed by running lower pressures anyway. So all is good . Now I just feel like an idiot for running 40-45psi for all those years.
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  19. #19
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    Quote Originally Posted by mr.niles
    in fact i do have timing device coming in the mail! yeah, it's hard to tell! that's why it's confusing to me. i'm always changing my presuures around to try and figure out what is best. i will try lower pressures, but i'm just not sure where to start. any ideas?
    The reason that most mtb tires are faster on dirt at lower pressures is really rather simple. A tire at lower pressure will flow or comform to bumps, smaller rocks, or square edged obsticals. A tire at higher psi doesn't do this, rather it has to make contact with the obstical and climb over it. This creates a bump that you can feel and in many cases the tire looses contact with the trail surface. It takes more time for the tire to bump over the obstical than it does to have it flow over it. The effects of higher pressure are, slower speed, less traction, less control. The lower pressure tire will have the opposite effect. But as the others have noted there is a limit to how low you can go. Rider weight, riding style, tire volume, tire construction, terrain, etc. all work to determine the "sweet spot" for a given tire. The sweet spot is that golden compormise pressure where the tire provides the best traction and performance without feeling squirmy or being so soft that you ding rims, etc. And I've never had two different tires that had the same sweet spot, and it takes a bit of work to find it. But if you go at it right it can be allot of fun.

    As for where to start, Surly29 had it right. Start with the lowest recommended pressure for the tire and ride it. If you don't get a pinch and the tire doesn't feel squirmy on the first run, drop pressure on the next run by 2 or 3 psi. If you do get a pinch or tire squirm up it by 2 or 3. So drag your pump and your bike to the trail and have fun. Oh and just as a side note, make sure you take a couple of spare tubes and have an inflation device along on the bike. Cause you will most likely pinch flat at least once.

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  20. #20
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    Spanw, believe Shiggy and all the others, they know what they're talking about with lower pressures. At your weight you should easily be able to ride anywhere from about 24PSI up to prob 35PSI for trails. It may not seem right, right now, but trust me When I first started I kept about 40 PSI in my tyres because it prevented pinch flats and helped them roll easier on the road. I've since come to realise that I needed the higher pressures with the tyre/rim combo I was using and my regular trail pressures now are between 24-30 PSI and I weigh 170lbs not geared up.

    Quote Originally Posted by Spawne32
    well im about 165 pounds and 40 psi in the rear is usually where i feel comfortable, adding a bit more flex to the front tire might make it a little easier on my arms but i dont know how much more difficult it would be to accel the bike forward with lower tire pressure. I might play around with it a little more now that i got my CST copperheads mounted today.
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  21. #21
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    Quote Originally Posted by trailville
    It's fine. Remember, that pressure is in a wider 2.3-2.4 tire. Once you feel how your tires can conform to rocks and roots rather than bouncing off of them, you will appreciate lower pressures. To be honest, I've never had issues with pinch flatting. I think part of it is due to the the mainly rounded rocks we have around here (thanks glaciers), and part is due to the fact that I started mtn biking on rigid bikes and even though I run suspension now (front and full), I still unweight the bike as I go over and through stuff.

    I've played with all kinds of pressures over the years. In the early 90s I started running between 30 and 35 psi because I was new to MTB and the people that knew what they were talking about recommended lower pressures (that seemed low to me at the time). Later on I got sucked into the "higher pressure is faster" thinking and started running 40 - 45. I also remember that some tires during the mid 90s started coming with separate pressure recommendations if you were riding suspension versus rigid (min pressure on suspension was like 5 or 10 psi higher), so since I was running front suspension then (if you can call a 63mm Judy suspension), I went with the recommendations.

    Eventually (years later) I got sick of bouncing and glancing sideways off of every rock and root on the trail and started lowering my pressures again. Then in more recent years I discovered wider 2.3 - 2.4 XC tires (I had been running 1.95s to 2.1s up to that point) and even lower pressures, and a whole new world opened up to me. I was more than happy to trade some speed for better traction and control, but then I started reading in these forums that I probably wasn't sacrificing speed by running lower pressures anyway. So all is good . Now I just feel like an idiot for running 40-45psi for all those years.
    Well said!
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  22. #22
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    Good job!

    Very well said trailville, Shiggy, Squash and others! How long will it take to beat it into people that lower PSI is better. I ride with guys that insist on running upwards of 45 PSI and if you are behind them you can see their tires bouncing all over the trail. When I mention lowering pressure mostly I get the response that they don't want to pinch flat and they brush me off . Oh well, their lose.

    BTW I'm 175 and on my Trek TF69er I run 22 PSI in the front Rampage 2.35 and 24 PSI in the rear Fat Albert 2.4, all tubeless with homebrew sealant (you should see my boogers!). And yes you can't just plow through rocks, roots and into logs. MTB riding should also incorporate at least a little finesse where you learn how to weight and un-weight the bike at the appropriate times.

  23. #23
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    Quote Originally Posted by Lugi
    I was curious to know what tire pressure is the best for all around xc use?
    I had IRC Mythos on my K2 and ran them very high because someone told me that I would get pinch flats left and right if I didn't.
    I now have Kenda Nevegals on my Cannondale Rush and was curious where people tend to have their pressure set. I normally ride pretty rocky/root filled technical terrain, with a little mud thrown in once in a while and some nice long downhills.
    Any suggestions would be great. Thanks
    This is like asking what shoe size to wear. It is greatly effected by tire size, the tire sidewall, your weight, and where you ride.

    I would start by lowering your pressure by a few pounds each ride until you either run into pinch flats or it just feels too soft.

    FWIW, I am ~185 with gear, and run ~23 psi front (2.4 Big Betty) ~30 rear (2.25 Ardent). East coast rocks and roots, but not much in the way of sharp edges.

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    i am curious about....

    what terrain and how you guys are riding it? shiggy, squash, trailville, lynx, kmacon, kapusta, le duke - how would you describe your riding style?

    i would have to say i ride like a gravity racer whenever the chance presents itself. when i brake, i cram the bike into the ground, when i corner i cram the tires onto their edge. i weight and unweight as quickly as i can, everywhere i can. i try to hit the best lines i can, but anytime the trail points downhill i am usually pinning it, so sometimes the best line is over the obstacles. of course this is not an absolute - there are pedestrians, horses, blind corners, etc that i always yeild to. but if i have a clear view, i push my limits.

    a little more remembering made me realized why i am running 36 psi in the rear tire: rim damage. long story shortened: several months ago i went out riding at one of my favorite places, riding it the way i like to ride it, and i had about 33-34 psi in my rear tire which seemed fine for the climbing and slower stuff. then i got to the fun part, and while bombing down the hill and really railing the corners something hit my rear tire so hard it bent the rim with a big "smack." i was very bummed because the rims are sun equalizer 29's and they weren't cheap. plus i had to do the whole junk task of changing a tube, not being able to pump it up enough etc, etc, not to mention losing out on finishing the bomb downhill because i had way too low pressure from not being able to pump it up enough. basically ruined the rest of my ride.

    on the other hand, 28 or even a little lower seems just fine in the front.

    another story: 2 weeks ago at northstar, i was having a great time riding all day with 36 psi in the rear tire (2 ply tire). then on my last run i decided to really pinnit down a somewhat rocky trail. i had a great run down, went to my car, loaded-up and went home. next morning had a flat on the rear - yep, big pinch slice. luckily i have big dh rims on that bike, so no rim dings.

    there have been other such incedences, but i will not include them here. overall, i have had the best "general" luck with 36 psi rear on a 2.1-2.35 tire with a single ply casing. maybe i am missing out on the benefits of lower pressure, but maybe i need the higher pressure to keep things together?

    so, does anyone think that i should still try lower pressures, or have i hit my "pinch limit" already? i will say that i HATE GETTING FLATS out on the trail, and i WILL NOT GO TUBELESS.

    i REALLY want to be able to go with lower pressures, because i DO know all about the tire conforming to the irregulaties using less energy to continue forward vs non-conforming, and i have ridden with lower pressures and experienced the way the tires "float" over the ground. but.....i have experienced problems going lower than 35 psi with the tires i like to use, so............

    ?????????????? what next????

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    Well Mr.Niles, first up I'll say this .......... Look into buying a GOOD frame [ump so if you get a flat you can inflate your tyre(s) back to whatever PSI you so desire Seriously if the POS you currently have can't even get you tyres back to 36 PSI, just toss it in the garbage, don't even think about it The pump I carry is a Topeak Mountain Morph and can inflate ROAD tyres back to 100 PSI when the need arises.

    Not sure how much skill I have or how hard I hit stuff, but so far I haven't managed to pinch flat a 29er My terrain down here in general is pretty slowish tech, with 1 or 2 DH's that have some rocks in them. I have one "nice" DH that I haven't ridden in over a year that's just a continous rock garden and last time I rode it was on my brand new Nano's, on my brand new RIP9, got way off line into the really rough stuff, faster than I normally ride the good line and didn't have a problem. However I will state that if I know I'm heading for that trail I prob run close to 30-32 PSI rear.
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    Wow thanks for the thread. I think I am convinced to drop my ridiculous pressures

    So the lowest recommended pressure on my Maxxis Crossmark tires is 35.

    I ride a heavy 32lb fs bike, weigh 200+ with gear and considering that I just got back into mtb after 10+ years of sitting on my arse, I ride like like a loose sack of bricks.

    So I'll try 35 on my 26er.

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    MN, Sounds like you...

    need to keep it just where you are. Everything is a compromise when it comes to tire pressure and what works for you. From the description of your riding style I wouldn't recommend tubeless unless you went full UST tires and wheels, and went with bigger tire, a true 2.35 or 2.4 and possibly DH casings. Tubeless isn't for everyone, there are allot of DH racers out there that won't run tubeless for some very valid reasons. Sounds like with the tires you're using, the terrain you ride on, and the way you ride, you've already found what works best for you. The only way you're likely to be able to go lower is changing equipment a bit. A larger volume heavier duty (read heavier as well) tire would likely let you run a bit lower and avoid rim damage and pinch flats. But if that isn't an option then your stuck. It sounds to me like your in that gray area where going with heavier duty equipment would hinder the rest of the ride, but would be appropriate when the trail points down. You're not flatting every ride, just occasionally. There are some options, but it doesn't sound like you really need or want them. It's one of those things, when your peggin' the fun meter there are times when you are going to exceed the capabilities of the equipment, in this case the tires. So your choices are, change the equipment, or try and keep the meter just off the peg.

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  28. #28
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    Quote Originally Posted by mr.niles
    what terrain and how you guys are riding it? shiggy, squash, trailville, lynx, kmacon, kapusta, le duke - how would you describe your riding style?
    I would agree with Squash: You've probably found what works best for you.

    As I said above, I'm on the east coast, so most riding is pretty rocky and rooty. However, not a lot of sharp racks. Also, compared to a lot of riding in NoCal (I lived in Tahoe for two years and rode a LOT) it is not as fast (lots of tight and technical, instead), and I think speed is a BIG factor. Things in general seemed more wide open out there (as with most places I've ridden out west), with more sharp rocks, and I was not able to run the kind of low pressures I do here. For riding around Tahoe I could get away with around ~27-28 front. I was not running the Big Betty up front when I lived there, so that may have let me go lower, but even with tires with less thick sidewalls (like what I ran out there) I can go down to 25 here in the front no problem.

    My riding style varies a lot, but if it is pointed downhill I try to hit it hard. That said, I think I must be a little smooth and/or slow because I seem to get less flats with lower pressure and thinner tubes than most people I know.

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    Quote Originally Posted by kboykin
    Wow thanks for the thread. I think I am convinced to drop my ridiculous pressures

    So the lowest recommended pressure on my Maxxis Crossmark tires is 35.

    I ride a heavy 32lb fs bike, weigh 200+ with gear and considering that I just got back into mtb after 10+ years of sitting on my arse, I ride like like a loose sack of bricks.

    So I'll try 35 on my 26er.
    And maybe think about trying some burlier tires. Your description of yourself, bike, and riding style doesn't say lightweight racing tire to me. Get something fatter with a little more meat to it and have lots more fun.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  30. #30
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    Quote Originally Posted by trailville
    And maybe think about trying some burlier tires. Your description of yourself, bike, and riding style doesn't say lightweight racing tire to me. Get something fatter with a little more meat to it and have lots more fun.


    Didn't realize the crossmark was a lightweight racing tire, yikes! My LBS rides 'em on the same trails and recommended them to me so I got them.

    Haven't ridden them much yet, first ride out on them this week I had a small log jump up and lodge into my back wheel bending my der. hanger and the back wheel out of true. Had the pressure at 40+ just because I don't know any better But they are a LOT better than the ancient crappy tires I was riding on.

  31. #31
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    Quote Originally Posted by mr.niles
    what terrain and how you guys are riding it? shiggy, squash, trailville, lynx, kmacon, kapusta, le duke - how would you describe your riding style?
    ...

    ?????????????? what next????
    I ride smooth and "light". Started 26 years ago and never owned suspension until 1987. Riding rigid teaches you to pick good lines, be smooth and easy on equipment. Transfer that to suspension and you are even faster. I ride over or around things rather than through them. Trail rider rather than hucker: I jump over things rather than jump off them. I work the bike to keep the terrain from working me.

    My local trails are fairly smooth with some rocks, lots of roots, but I do not really change my tire pressures when I go elsewhere, like Downieville or Gooseberry Mesa. I was running 28/30 psi in 2.2" tires on a hardtail with a 80mm fork at Downieville. Was at the front of the group on the lesser-known trails and slipped to the middle when we reached the main routes (I have little local knowledge of them). No flats, no cuts, no dinged rims.

    In Utah I ride rigid, 2.2-2.5" tires, 18-26psi. In ~4 weeks (20+ rides) of riding there I had 2 pinch flats: both from slamming rock ledges while not paying attention.

    In the early '90s I was at an XC race that used fast, rocky moto trails. I passed many riders on the descents and finished in the top 10% of the field. Afterward the guys parked next to me complained "I was using 50psi and I still flatted!" (and with suspension forks). I was rigid, 2.2', 32psi front; 1.8", 36psi rear (when tires were "smaller"). No flats. Passed people because I could steer around the big rocks rather than bouncing off of/into them.

    Even on my Coiler "big hit" bike (6" travel, Marz 66 fork) the pressures are low (and the tires big) and the riding style does not really change. I may take rougher lines and ride off bigger lips but I still do not just plow in and expect the bike to suck it up. Last year I rode one of my favorite sections of trail several times, a 5 mile remote singletrack downhill filled with embedded rocks, big roots and tight lines. First on the Coiler w/2.4" tires, later on my hardtail w/100mm fork, 2.3" tires. Each time I took basically the same lines, took the same time to complete the section and had a blast. I did work harder on the HT, but I did not feel I could have safely gone any faster on either bike. A buddy (riding a fully) following me, commented that I looked like I was on a 5" fully while riding my HT. Smooth and fast.

    What next for you? Bigger tires (volume) if you want to try lower pressures. Higher volume generally means you can use lower pressures as long as the tire is still well supported. Every rider is different in what works for them. You either adapt your equipment, or adapt your riding style. If you can do both, so much the better. And remember that with suspension, the tire pressure is as important as the shock settings. Change one and you may need to change the other for best results.

    And the real bottom line: If you are fixing a flat, or crashed along the trail, you are not going very fast.
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  32. #32
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    Ah, yeah That's what they are all right. Definitely a good tyre, but even I know that they're not a tyre suited to the riding style you describe. Try something more beefy like some Schwalbe Big Betty's, WTB MutanoRaptors, Maxiss Ardents, Panaracer Rampages, Kenda Nevegals all in the 2.3-2.4" range.
    Quote Originally Posted by kboykin


    Didn't realize the crossmark was a lightweight racing tire, yikes! My LBS rides 'em on the same trails and recommended them to me so I got them.

    Haven't ridden them much yet, first ride out on them this week I had a small log jump up and lodge into my back wheel bending my der. hanger and the back wheel out of true. Had the pressure at 40+ just because I don't know any better But they are a LOT better than the ancient crappy tires I was riding on.
    One day your life will flash before your eyes, will it be worth watching??

  33. #33
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    Quote Originally Posted by LyNx
    Ah, yeah That's what they are all right. Definitely a good tyre, but even I know that they're not a tyre suited to the riding style you describe. Try something more beefy like some Schwalbe Big Betty's, WTB MutanoRaptors, Maxiss Ardents, Panaracer Rampages, Kenda Nevegals all in the 2.3-2.4" range.
    Depends on which Crossmark. I have a set of 2.25 UST that are pretty beefy and are good trail tires. The standard 2.25 is not bad either.
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    Good job!

    I'm thinking that this thread should become a sticky, as always Shiggy knows what he's talking about...Even now I'm experimenting with pressures and this thread has me reaching for the lower pressures.
    What I started with recently was "Eskars performing best at 28-30 PSI whether tubbeless or tubed" MBAction...

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    sqaush and shiggy and kapusta, thanks a bunch for the advice and good stories! lynx, i'm going to get one of those pumps to put in my pack when i go into the wilderness areas.

    i will most likely stay with my existing setup unless i can find a larger volume tire that has comparable weight, tread pattern, compound to the maxxis high rollers (which i'm having good experiences with right now).

    shiggy......."Every rider is different in what works for them. You either adapt your equipment, or adapt your riding style. If you can do both, so much the better.'.......i am always attempting to do both, with the emphasis on the later. really this all about having fun, but fun to me is riding the best i can. so i am constantly working on my technique(s). shiggy you have your riding dialed. i agree that a hardtail is a terrific platform to train on in rough terrain. today i did 3 hours of cornering and slalom drills with cones. i have fun doing that sort of thing. it's most important to me to be a good rider. because if i'm a good rider, less than perfect equipment won't matter much, and i'll still have a blast!

    once again, thank you all for the help.
    Last edited by mr.niles; 10-09-2009 at 09:48 PM.

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    kapusta, thanks for your insite about tahoe. it turns out that tahoe, and especially northstar bike park, are my yardsticks for bike setup and durability. if it can survive a weekend at the star, then it will live thru anything else i am likely to put it thru. also, because i have so much fun riding there, i tend to go looking for places with similar qualities for my rides. so, maybe that is the common denominator for my bike setup. i do make some equipment changes for regular trail riding, but my durability testing takes place in tahoe.

    hmmmm.....ok, now that we are talking about northstar, i forgot to mention that i do jumps and hucks on all my bikes, so everything on them has to survive that, too.

  37. #37
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    add wtb prowler xt's

    Quote Originally Posted by LyNx
    Ah, yeah That's what they are all right. Definitely a good tyre, but even I know that they're not a tyre suited to the riding style you describe. Try something more beefy like some Schwalbe Big Betty's, WTB MutanoRaptors, Maxiss Ardents, Panaracer Rampages, Kenda Nevegals all in the 2.3-2.4" range.
    i have done some serious torture testing of these and they came thru with shining colors - and excellent traction.

  38. #38
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    Ah yes, my bad, have to try and remember that not everyone is riding a 29er - yet A guy I sometimes ride with has some 26" x 2.1" LUST Crossmarks and they're definitely a beefier sidewall than the standard version, but I wouldn't put them up for the same duty/terrain I'd trow on a Rampage or Nevegal - for down ehre the Xmark tread is plenty.

    Quote Originally Posted by shiggy
    Depends on which Crossmark. I have a set of 2.25 UST that are pretty beefy and are good trail tires. The standard 2.25 is not bad either.
    One day your life will flash before your eyes, will it be worth watching??

  39. #39
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    Great thread! I had no idea.

    After going through everyone's views, it tells me to move to the "dark side" (lower air)! I was running 35psi front and rear on my Schwalbe Albert 2.25's. I think many of us old school riders do the same mistake. I ride cross country.

    I run a 100mm FS bike. I weigh in at 195 without gear. Now I have a Highroller 2.35 rear and Nevagal 2.5 on the front. Both are folding and tubed. Brand new tires.The experimenting should get interesting.

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  40. #40
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    Cool Thread

    There was a thread in here a year or two ago which detailed a study of rolling resistance for mountain bike tires. The basic conclusion was that high pressure worked well on pavement ONLY. Lower pressure created less rolling resistance on rugged terrain. They even had resistance measures for long grass. It was a very scientific undertaking, and got me to run as low as possible.

    28 front and back, 175 lbs. Prophet with 150 in the rear shock. Learned on a hardtail, still use that stuff.

  41. #41
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    Quote Originally Posted by Lugi
    I was curious to know what tire pressure is the best for all around xc use?
    I had IRC Mythos on my K2 and ran them very high because someone told me that I would get pinch flats left and right if I didn't.
    I now have Kenda Nevegals on my Cannondale Rush and was curious where people tend to have their pressure set. I normally ride pretty rocky/root filled technical terrain, with a little mud thrown in once in a while and some nice long downhills.
    Any suggestions would be great. Thanks
    A lot depends on the shape of the rocks.

    In Idaho I pinch-flatted once or twice in about 20 years of riding with 25 psi front and 30 in the back.

    Here in Arizona I've pinch-flatted as high as 38 PSI on a true 2.25 tire when I didn't notice a small square-edged rock in time and slammed into it. 36 PSI in the rear is pretty much a guaranteed pinch flat for me unless running ghetto tubeless or true tubeless.

    I've even pinch-flatted my front road bike tire at 100 PSI on a small rock, because that rock was crushed gravel and had a sharp edge. (That's what we use instead of grass around here -- we save our water for the golfers ).
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  42. #42
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    Quote Originally Posted by hikerdave
    ...I've even pinch-flatted my front road bike tire at 100 PSI on a small rock, because that rock was crushed gravel and had a sharp edge. (That's what we use instead of grass around here -- we save our water for the golfers ).
    And the volume of the tire. The piece of gravel on pavement is also much more likely to cause damage than if it is on hardpan dirt.
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  43. #43
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    a rookie's q:
    what is pinch flat? how to determine it? i just heard about the jargon..
    TIA

  44. #44
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    Quote Originally Posted by nbayu
    a rookie's q:
    what is pinch flat? how to determine it? i just heard about the jargon..
    TIA
    Pinch flat
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  45. #45
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    As high as possible, without losing traction in the corners..

    Quote Originally Posted by Lugi
    I was curious to know what tire pressure is the best for all around xc use?
    As high as possible, without losing traction in the corners..

    that would be 28 to 31 psi.

  46. #46
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    Quote Originally Posted by shiggy
    Depends on which Crossmark. I have a set of 2.25 UST that are pretty beefy and are good trail tires. The standard 2.25 is not bad either.
    Hmm thanks for the input. Not sure which one I have. They are 2.25, the lesser TPI (60?) and the harder compound.

    They seem flimsy to me by touch, but I'm used to cheap old tires so I figured it was not something to judge them by.

    I'll just ride them until they destruct. Trails I ride are rocky and rooty single track. Frequently ding my rim and scrape the side of my tires on large rocks and small stumps.

  47. #47
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    If you had the LUST version, trust me you'd know it They have a huge a$$ LUST logo on the side in yellow if I remember right, so no mistaking them with the normal ones - you have the normal casing version.

    Quote Originally Posted by kboykin
    Hmm thanks for the input. Not sure which one I have. They are 2.25, the lesser TPI (60?) and the harder compound.

    They seem flimsy to me by touch, but I'm used to cheap old tires so I figured it was not something to judge them by.

    I'll just ride them until they destruct. Trails I ride are rocky and rooty single track. Frequently ding my rim and scrape the side of my tires on large rocks and small stumps.
    One day your life will flash before your eyes, will it be worth watching??

  48. #48
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    I had forgotten how cool low tire pressure works ,but on a solo wet ride rescently, i let some air out of my tires (not very scientificly)but they worked awesome for a couple of hours , then i got a little carried away on a downhill section and pinch flatted. A pinch flat is a puncture that is on the inside area of the tube, it is not caused by something piercing through the tire ,it's the tube being smashed between your rim and a rock,a snake bite(common expression)is a type of pinch flat that happens with both sides of the rim,you'll have two punctures that always seperated by the width of the rim,the holes tend to look like little slits too not a round shaped pucture that a thorn or nail would make. If you run tubeless at good pressures for wet slimmy conditions you may get burping,when the tires flex to their limit and release a bit of air for a second,you should stop and refill the air as soon as you can , a couple of burps and your tire bead could come totally loose.

  49. #49
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    Awesome! Just the thread I was looking for. On Friday I ran 40/40 on my first ride on my new rig, (see below). The climbing was great but the downhill....there was this moment. While coming around a left turn at around 25 mph I hit a rock. The front end was propelled about a foot to the right. The bike hooked up immediately but it was still a "moment" and most likely increased my average hr. Sooo, lower presure for the front it is! I'm gping to lower both tires now thanks to this thread.
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  50. #50
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    Quote Originally Posted by herbn
    I had forgotten how cool low tire pressure works ,but on a solo wet ride rescently, i let some air out of my tires (not very scientificly)but they worked awesome for a couple of hours , then i got a little carried away on a downhill section and pinch flatted. A pinch flat is a puncture that is on the inside area of the tube, it is not caused by something piercing through the tire ,it's the tube being smashed between your rim and a rock,a snake bite(common expression)is a type of pinch flat that happens with both sides of the rim,you'll have two punctures that always seperated by the width of the rim,the holes tend to look like little slits too not a round shaped pucture that a thorn or nail would make. If you run tubeless at good pressures for wet slimmy conditions you may get burping,when the tires flex to their limit and release a bit of air for a second,you should stop and refill the air as soon as you can , a couple of burps and your tire bead could come totally loose.
    Snake bite and pinch flat are basically the same thing. A pinch flat is as you describe, but the tube is folded when it gets pinched, so often (but not always) this results in two holes on the same side, of the tube, thus the "snake bite". When it happens on both sides of the rim, that is just two pinch flats (and possibly two snake bites).

  51. #51
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    Quote Originally Posted by kapusta
    Snake bite and pinch flat are basically the same thing. A pinch flat is as you describe, but the tube is folded when it gets pinched, so often (but not always) this results in two holes on the same side, of the tube, thus the "snake bite". When it happens on both sides of the rim, that is just two pinch flats (and possibly two snake bites).
    And I have never seen the latter in 25+ years of mtbing. It may appear that the snake bite holes are at rim width but they do not line up properly for that to be how it happened if you look at their position on the tube.
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  52. #52
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    Quote Originally Posted by shiggy
    And I have never seen the latter in 25+ years of mtbing. It may appear that the snake bite holes are at rim width but they do not line up properly for that to be how it happened if you look at their position on the tube.
    That's because you ride with people who, unlike me, are smart enough not to try to ride up a concrete staircase with under inflated tires, no finesse, and a really good running start. The double snake bites were the least of my problems.

  53. #53
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    Read you tires. Most XC tires run optimally at 2 Bar. 29lbs.
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  54. #54
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    Quote Originally Posted by Ruger
    Read you tires. Most XC tires run optimally at 2 Bar. 29lbs.
    You ARE joking, right?

  55. #55
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    Quote Originally Posted by Ruger
    Read you tires. Most XC tires run optimally at 2 Bar. 29lbs.
    Ummm...I refer you to your own signature.
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  56. #56
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    I run 32 and 35lbs on a Highroller 2.35UST mounted on an XM819 rims on my 2004 5-spot...

    my problem is not the traction or pinch flats but rim dents that eventually cannot be re-trued again...

    I ttry to ride smooth and choose the best line as much as I can but the are time that rocks on the trails cannot be avoided

    What shall I do then???
    When trails gets tougher, Just stand up and deliver.

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    food for thought....

    i recently had a chance to ride some very fun trails somewhere near santa cruz - you know the ones......with perfect soil after a bit of rain, and almost no rocks, i tried lowering my pressures to about 24-25 psi front and about 32-33 psi rear. in that perfect soil, and on those particular trail-side attractions in that place some of you may know about, i got unreal traction with a smooth buttery ride quality.

    so, soil conditions will tell you what you can get away with on your pressures. i was able to lower my pressures in sc, but at northstar in tahoe, at 24/32 i'd be pushing my bike down the hill to go buy a new tube.

    very cool that this thread is a sticky. it has become very informative.
    Last edited by mr.niles; 11-05-2009 at 09:27 PM.

  58. #58
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    Quote Originally Posted by kapusta
    Snake bite and pinch flat are basically the same thing. A pinch flat is as you describe, but the tube is folded when it gets pinched, so often (but not always) this results in two holes on the same side, of the tube, thus the "snake bite". When it happens on both sides of the rim, that is just two pinch flats (and possibly two snake bites).
    either way, your tube is toast, you are pushing your bike, and you are bummed.....

  59. #59
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    28psi with conti mountain king 2.4s

  60. #60
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    Wow after reading this thread this may sound crazy, I weigh 150 pounds and I ride my hardtail at 60 psi. I never thought of lowering them, but now I'll give it a try.

  61. #61
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    Here is a quote of mine from another thread (561602)

    I just finished my local series here in the Ottawa area at Camp Fortune and its rough and rocky. Always several guys flatting each race. I switched half way through the season from the Karma to the Nevegals and have since had my best times.

    I'm starting to worry less about tire weights and more about traction and running correct pressure. Running tubed 25F/23R on Nevegals 2.1 and 30F/28R on Karmas(2.0) (5'4" 145lbs) with only one pinch flat all summer on a high speed decent having to take a poor line do to some hikers


    Take a few extra tubes when you want to experiment wih tire pressure. Try running lower and lower pressure till you pinch flat and then run 2-4 psi higher after that. Works great for me.
    I found there can be a HUGE difference in traction, or rather lack of it, when running your tires at too high a pressure. Of course your riding trails and style could effect optimum tire pressure. Aside from fixing the odd flat it can be fun to mess around with pressure and traction etc as long as you are prepaired for it and it ain't a race haha

    Cheers,
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  62. #62
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    160lbs rider, Niner Rip (29er for those not familiar)

    Continental Mountain King 2.4 front 19psi
    Stans Raven 2.2 rear 23 psi

  63. #63
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    I run 35-40 psi in my Nevegals on a full suspension bike.

  64. #64
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    What would you all recommend for someone 113 lbs?

  65. #65
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    A good meal!

  66. #66
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    Quote Originally Posted by Nikhil42
    What would you all recommend for someone 113 lbs?
    Reading the whole thread so you learn how to find your own best pressure.
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  67. #67
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    I weigh 185 with gear and was getting rim damage on my mavic 819's with tires lower than 45psi in the Sierra Foothills (some of the higher g creek crossings were the offenders). I feel like an idiot for buying UST as the whole point was to run them at low PSI, but that only destroys the wheels. I've been riding this pressure for some time and feel comfortable on it. My next wheels will be tubed for sure.

  68. #68
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    Quote Originally Posted by Dirge02
    Wow after reading this thread this may sound crazy, I weigh 150 pounds and I ride my hardtail at 60 psi. I never thought of lowering them, but now I'll give it a try.
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  69. #69
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    running at 50 in both tyres think it's time to drop them to 40
    i'm approx 220lbs so a bit on the heavy side

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    As low as you can go fellas. That low pressure squirm can be unnerving at first, but you will get a handle on it and you will be railing corners faster than ever.

    I love seeing newbs (and even better, vets) running their tires rock hard and they wonder why they don't get traction, while on the other hand they point out my tires are nearly flat

  71. #71
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    I run Kenda Karmas(2.0) and Nevegals(2.1) and even tho the Nev is about 200g a tire heavier my times are about the same on both tires. I run 28 ish on the Karmas and 23 ish on Nevegals. I get WAY more traction on the Nevs.
    I think my best time ever (on local track) was on the Nevs, but was later inthe season and was probably fitter

    Anyone else find they like racing on a larger volume tire with lower pressure even with the weight penalty???

    Cheers,
    Paul Bell

  72. #72
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    This all makes sense but for clydes like me @ 245 it seems like a trade off. There was mention of speed but not much about rolling resistance. When I ran 28/38 which seemed to give me plenty of support, the confidence and traction on the trail was huge. The trade off is it felt like I was riding through a foot of molasses on a relentless uphill with a headwind. If this were my first day out, I probably wouldn't think MTBing was very fun. I'll admit the RR was not as bad in the dirt as it was on pavement. For me, it seems the low pressure is more approriate for downhill. I'm riding with more pressure and slowing for the technical stuff.

    Edit: Ok, went for another ride and realized I was riding uphill with a headwind. Santa Ana's for the last few days. Yes there was noticeable rolling resistance but not too bad. This time pressure @ 20/30. Front is fine but I think the rear needs some more air and the tires stick like velcro. In fact, the tires grip so well the there IS more resistance on pavement.
    Last edited by h82crash; 03-17-2010 at 09:40 PM.

  73. #73
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    Old habits die hard, it's a great thread to convince you to try lower.

    Recent rides on my own no problems in the dry, with a group on a littered trail of shale, wet and muddy and underlying smooth and square fist sized rocks. The bike felt quite harsh. It makes you realise even 3-4 Psi too much can affect handling. this from a rider 155lbs on Maxxis minion 2.35 so looks like 22 Psi give or take seems ideal as 25Psi on that track felt very scary.
    One of the biggest mistakes i have done over the years is not spent the time out in the field shock pump tyre gauge and a series of loops.

  74. #74
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    Same thing here..

    I went tubeless on my new bike two weeks ago.
    I set the tire pressure 25-28 front and rear then went for a ride....
    I just kept reducing the pressure until the handling felt perfect to me.
    When I got back to the car I checked the pressures and I couldn't believe it.
    20 psi in the front and 23 psi in the rear. I'm running Specialized Fast Traks 2.0 front and rear.
    I'll do the same thing tomorrow just to make sure!
    Climbing cornering even flat out hammering just felt effortless.
    Low pressure really makes a difference!
    Oh I'm 155 pounds with gear.
    Spend time to play with the pressure and go with the feel.

  75. #75
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    I run 40/40, im also 210..I always worry about pinch flats riding hard. I pump them to 40 then stop worrying about messing with pressure.

    I have used the mythos tires before and i got a lot of pinch flats with them..they also wore really fast. They are very good tires with lots of grip and they are very light.

  76. #76
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    recently ran 17psi in 2.1 Renegade's on a wider rim (Easton Haven)...it was a wierd ride - if i was super smooth everything was good. But, if I gave some serious input then the tire squished too much and I could feel some roots hit.

    So the deal is, with UST run low psi until the above starts happening. 1.5bar, and 21psi are magic numbers for bigger tires.

    I am 180lbs, so I am heading 24psi in the front, 25-26psi rear. These lower PSI's give more traction and thus you can run a lower hieght knob, and a faster wider tire.

    To the people that WONT GO TUBELESS, then they are at a dead end, I would say they can only go down to 30psi with a bigger casing and 35psi with a 2.0 sized tire...and thats only at my 180lbs wieght....any heavier then up the PSI.

    later...LC

    PS: UST rims, and any tire with sealent works - Guetto tubeless add 5-10psi just for reliablity!

  77. #77
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    Quote Originally Posted by twenty6black
    recently ran 17psi in 2.1 Renegade's on a wider rim (Easton Haven)...it was a wierd ride - if i was super smooth everything was good. But, if I gave some serious input then the tire squished too much and I could feel some roots hit.

    So the deal is, with UST run low psi until the above starts happening. 1.5bar, and 21psi are magic numbers for bigger tires.

    I am 180lbs, so I am heading 24psi in the front, 25-26psi rear. These lower PSI's give more traction and thus you can run a lower hieght knob, and a faster wider tire.

    To the people that WONT GO TUBELESS, then they are at a dead end, I would say they can only go down to 30psi with a bigger casing and 35psi with a 2.0 sized tire...and thats only at my 180lbs wieght....any heavier then up the PSI.

    later...LC

    PS: UST rims, and any tire with sealent works - Guetto tubeless add 5-10psi just for reliablity!
    No, it depends on the rider, tire, rim and terrain. I am currently running Panaracer GC CX 2.1s with tubes on 24mm rims under 25psi on hardpack to rocky terrain.180 pounds, hardtail bike. I can go lower with wider rims.

    I do/can not go lower with similar volume tubeless tires.

    p.s. Not all DIY conversions work. Standard tires without tubes require more pressure to prevent squirm. Use at your own risk.
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  78. #78
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    Quote Originally Posted by twenty6black

    To the people that WONT GO TUBELESS, then they are at a dead end, I would say they can only go down to 30psi with a bigger casing and 35psi with a 2.0 sized tire...and thats only at my 180lbs wieght....any heavier then up the PSI.

    later...LC
    Hey LC, I have to disagree with going tubeless is the only way to go.

    I run tubes and I don't have a problem running low pressure. As I stated earlier in the post I am 140ish with a 30ish lb XC bike. I have been running 2.1 Nevs @ 23 ish pounds the end of last racing season and now this season. I am not getting any more flats(very rare) compared to the tubless guys (flatting or burping) in my group. I can see that I am not spinning any more than the tubleless guys. I clear tough sections (without flatting) and I am one of the newest guys in the group.

    IMHO key things are TERRAIN---RIDER WEIGHT---RIDING STYLE combined .
    If you are not willing to experiment with pressure and changing the occational flat then pump em up to the sidwall specs and go, with a trade off on traction, comfort, and possibly speed.
    Maybe this is a good argument to go tubeless(if you just want to pump em up and go)( I believe sidewall pressure specs are lower for tubeless tires ???YES/NO???)

    Cheers,
    Paul

  79. #79
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    Quote Originally Posted by twenty6black
    recently ran 17psi in 2.1 Renegade's on a wider rim (Easton Haven)...it was a wierd ride - if i was super smooth everything was good. But, if I gave some serious input then the tire squished too much and I could feel some roots hit.

    So the deal is, with UST run low psi until the above starts happening. 1.5bar, and 21psi are magic numbers for bigger tires.

    I am 180lbs, so I am heading 24psi in the front, 25-26psi rear. These lower PSI's give more traction and thus you can run a lower hieght knob, and a faster wider tire.

    To the people that WONT GO TUBELESS, then they are at a dead end, I would say they can only go down to 30psi with a bigger casing and 35psi with a 2.0 sized tire...and thats only at my 180lbs wieght....any heavier then up the PSI.

    later...LC

    PS: UST rims, and any tire with sealent works - Guetto tubeless add 5-10psi just for reliablity!
    Depends on your terrain and style of riding.I'm 170 lbs, I ride forest trails[ no rocks or thorns] and have been riding tubes at 25 psi for 15+ years. One of my current fav tires for some conditions is a Nobby Nic 2.4 snakeskin. It gives best traction when run on the front 28mm rim with a tube at 20 psi.Ghetto tubeless I would probably run it 23 to 25 PSI[ no support from a tube].

  80. #80
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    Some useful info on tire pressures and rolling resistance here

    http://www.schwalbe.co.uk/shopdata/f...chInfo2-GB.pdf

  81. #81
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    Is my pump gauge ok?

    I didn't bother about tyre pressure until I read some threads and bought a full rigid 29. The absence of suspension fork drove me to low pressures.
    I don't have a gauge to measure the pressure at trails. At my first ride I reduced the pressure to the point I felt the bike rolling smooth; I was sure I could go lower without worrying about pinch-flats or damage the rims. When I returned home I checked the pressure at Nevegals 2.2 and my floor-pump gauge show 15psi front and 18psi rear (I know pump gauges are not so accurate). My weight is 158lbs (72kg).
    With my old 26 ht I was running my tyres at hight pressures and its ride was so harsh! Now I know how important is the "right" pressure in tyres. Maybe the right pressure is different for everyone but don't be afraid to try lower pressures, you will be surprised .

  82. #82
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    tubeless stuff

    Quote Originally Posted by gvs_nz
    Depends on your terrain and style of riding.I'm 170 lbs, I ride forest trails[ no rocks or thorns] and have been riding tubes at 25 psi for 15+ years. One of my current fav tires for some conditions is a Nobby Nic 2.4 snakeskin. It gives best traction when run on the front 28mm rim with a tube at 20 psi.Ghetto tubeless I would probably run it 23 to 25 PSI[ no support from a tube].

    yep...the above are good guidelines....everyone jumps into (onto) the tubeless topic - love it!

    Here is something that just happened to me....mud race had the Easton Haven's 21mm rim width, with 2.2 MK SS run them tubeless, so I can go low on the pressures - ANYWAY....didnt lower the pressure for the race - ended up runing 30+psi in the front and 35+psi in the rear !!! I kenw there was a problem right at the start - i could feel every rock and root.

    sooooo...I took it easy on the rock and roots - thing is, the mud sections I was getting good grip - knobs digging through to hard soil - and the double track BAAM - major speed!

    So the MK 2.2 clears the mud and digs for traction, and when run at higher pressures (higher for me) they roll amazingly fast.

    I have also run them at lower pressures and the traction goes UP - speed on hard pack goes down a wee bit.

    This race turned out good - more from good luck than good management.

    ...LC(cheers)

    PS: lesson is, higher pressure on a kobby tire are cool for mud events!

  83. #83
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    I run 50 psi front and rear on a Stumpjumper. I'm 215 with gear.

  84. #84
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    I'd like to chime in. Everyone who hasn't gotten that high volume tires and low pressure is the way to go by now, really should wake up and leave 1994.

    I weigh 215# without gear on, and I run 22psi in the rear and 18 in the front on trails with my FS with Big Betty 2.4's, and 25/23 psi on fire roads/pavement with my hardtail and Rocket Ron 2.4's. I roll faster than the 2,0"
    semi slick guys with their 50 psi pressures (off the tarmac at least), and have way more comfort.


    With tubes, but on XTR Flow and Crest rims. I can't remember my last pinch flat. Must be years ago.

  85. #85
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    I find your weight is generally proportionate to your hand strength and therefore I use the it's soft enough to get a good squeeze on the front and only a moderate squeeze on the front

    This the lower the better mentality started from the Stan's users is well ridiculous, yes you can run it that low cause of no pinches but you've got to run it harder than with tubes cause 1 less layer of rubber, and ran really low, tires squirm, side walls give out randomly causing a sharp fall over sensation or even a fall over.

    That and modern tyres the casing is so soft, if you run them flat the knobs fold in on contact with the ground and you might aswell be running slicks, and slicks ran low on rocks / road would still out grip mtb tires, until you hit mud.

  86. #86
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    Dazed I'm your weight and with a tougher higher volume tire ( RQ 2.4 ) with a fat rim ( EX729 ) I get 24psi, 22psi I can feel the roots hitting the rim, 26 and it feels rigid ( the effect of HUGE tires ) no way can I get near 18 on the front without it feeling like it's flat.

    Obvously you have to allow hugely for guages being really in accurate at these kinds of pressure.

  87. #87
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    Quote Originally Posted by Turveyd
    Dazed I'm your weight and with a tougher higher volume tire ( RQ 2.4 ) with a fat rim ( EX729 ) I get 24psi, 22psi I can feel the roots hitting the rim, 26 and it feels rigid ( the effect of HUGE tires ) no way can I get near 18 on the front without it feeling like it's flat.

    Obvously you have to allow hugely for guages being really in accurate at these kinds of pressure.
    I have two standalone gauges (Schwalbe Airmax Pro and Topeak Shuttle Gauge), and I know what I feel. I may not ride very rough, but I don't flatten the tires.

    I doubt the RQ is any bigger or sturdyer than a BB. My tires aren't squirmy at all. The RoRo's would be at that pressure, but not the BB's.

    It's a very individual thing, of course.

  88. #88
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    The RQ2.4 is the biggest volume tyre I've seen and with 180tpi in the side walls ( Apex casing ) it's pretty solid aswell, the 29mm internal DH rim helps aswell.

    Shame there so expensive, but no visible wear on mine on the front so not really a worry if I can get a year out of it.

  89. #89
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    Those wide rims make a difference of course, even though the flows have Stan's "BST" bead hooks ( http://www.notubes.com/images/height-compare.gif )adding to the width and volume, 29mm is WIDE.

    Shiggy / mtbtires.com backs you up on the RQ being bigger, btw. Too bad, 'cause i don't think my Ventana frame can deal with ANYTHING bigger than the BB. ...And now I know something bigger exists!

  90. #90
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    I don't have issues with pinch flats and I have dropped my pressure based on this thread. Can't honestly say the RR is less with lower pressure. I recently showed up to a group ride (a really fast XC group) with my all mountain/rocky trail pressure and I very soon got a "you better put some air in your tires." from folks that just looked at my tires. Took like 50 psi rear to get them as firm as the rest of the group. Kept front to about 30. Wow, what a difference! I still couldn't keep up with them but it didn't feel like riding velcro tires on carpet anymore. I'll drop back down for my regular rocky bombing but for the XC stuff, I'm checking to see if some road wheels will fit.

    Most of the group were running 1.95s and few were larger than 2.1. Maybe "all around xc" is different from serious xc race?

  91. #91
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    Dazed, I run the RQ 2.4 in a 29er fork so loads of room Not many regular forks they'd work in, front only aswell I'd say, to draggy on the rear for me.

    I actually bought it to run with my Rigid bike, which uses the 29" wheel and a Ardent 2.4 ran soft ish, although not as big it still handles roots and rocks rigid better than the RQ2.4, but the RQ2.4 out grips it.


    Seriously pressure sensitive from roots hurt to you can't feel the roots with just the smallest amount of air let out, then to the jarring rim contacting sound no pinches yet though. and I bust my right thumb 2 weeks back so my own gauge is off

  92. #92
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    No gauge, huh... Well, I was surprised how "hard" 20 psi feels in a whooping big 2.4" tire. maybe you'll find that you're actually running lower pressures than you think if you check with a good gauge?

  93. #93
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    Mates got a gauge though, as I state your gauge very likely isn't accurate, it's obviously means the same for my mates.

  94. #94
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    And as I stated, I've got several gauges showing the same pressure.

  95. #95
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    Just discovered this thread. It is interesting that no-one has actually stated the physics first.

    1. For a given tyre pressure your contact patch size will stay the same regardless of the tyre size. Read that again. So a 2.5" tyre will have the same contact patch area as a 1.9" tyre @30psi, or @25psi or whatever.
    2. What will change with changing tyre size is the shape of the contact patch. The wider the tyre, the shorter and fatter the contact patch. But the size will stay the same.
    3. With the changing shape of the contact patch, the dynamics of the tyre will change in the 4 axis that a tyre works on (the "friction circle") - front and rear for traction/braking, and side-to-side for cornering.
    4. Generally speaking chose a narrow long contact patch for better traction & braking, and a wide short patch for cornering.

    That is the physics.

    What is also true, as someone has stated is that at lower pressures a tyre will deform to absorb a small obstacle where a tyre at higher pressure will resist deformation and ride up over the obstacle. Whether this is a "good thing" depends on the terrain, the speed and your objective.

    At one extreme, hard-packed surfaces, you work to present the smallest contact patch that you can. Using smaller tyres and higher pressures. There will be nothing faster. That is why roadies run 19c tyres @130psi for races.

    For other terrain, you need to balance speed, traction, cornering and braking to find the right combination to go fastest. This will be a combination of tyre size, pressure and tread pattern. There is no hard-and-fast rule here. You will find some tyres will be faster at higher pressure than other tyres run at lower pressure when sense says they shouldn't be. Why? Because the tyre manufacturer has developed a casing optimised for the conditions you are riding, and the tyres are fast.

    For this reason, I work on tread/compound first, size second, then pressures third.

    However, I have about 20 tyres in the garage and 3 sets of wheels setup. One with a general XC tyre-set, another with a more radical XC race set, and one with a wide software "traction" set for wet weather.

  96. #96
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    What is also true, as someone has stated is that at lower pressures a tyre will deform to absorb a small obstacle where a tyre at higher pressure will resist deformation and ride up over the obstacle. Whether this is a "good thing" depends on the terrain, the speed and your objective.

    At one extreme, hard-packed surfaces, you work to present the smallest contact patch that you can. Using smaller tyres and higher pressures. There will be nothing faster. That is why roadies run 19c tyres @130psi for races..
    I think it is said that you loose more energy in the vibration and bouncing of the bike from a harder tire (from pressure) than you do from the energy lost deforming a softer tire over a bump.
    It must also be noted that there is optimum tire pressures for road tires. Its not pump them up to next to the blowing point. For example at my weight my tire pressure for my Michilen Race is around 90 psi, while a heavier rider needs more.

    It's also funny how all your theories get thrown out the window buy smoking your best time running the bigger heavier tire with lower pressure(Nevegal 650g) on a day when its dry and fast and you figured being to lazy to switch to the lighter higher pressure tire (Karma 400g) was gong to hurt you
    Last edited by Rum Runner; 10-01-2010 at 06:10 AM.

  97. #97
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    Actually, based on my analysis of the physics involved, I found that I had a larger contact patch when running skinnier tires at high pressure. This was due to the fact that my feet were touching the ground far more often.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  98. #98
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    Quote Originally Posted by Rum Runner
    It's also funny how all your theories get thrown out the window buy smoking your best time running the bigger heavier tire with lower pressure(Nevegal 650g) on a day when its dry and fast and you figured being to lazy to switch to the lighter higher pressure tire (Karma 400g) was gong to hurt you
    That is also a point that is worth re-affirming. It is very very hard to have a consistent measure to evaluate tyre/wheel performance against. A long time ago I setup a trial of aero rims as a few of my mates and I were deeply into triathlons. We have a evaluation circuit of about 5 klicks taking in a variety of types of surface, hill, flat and downhill (obviously). We were all very fit and strong, and yet there was about 5% variability in our circuit times on the same day, on the same equipment. It makes it very hard to scientifically measure with the "control" being so variable..

    I would also state the obvious. Feeling fast and being fast against the clock are different things...

  99. #99
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    Quote Originally Posted by trailville
    Actually, based on my analysis of the physics involved, I found that I had a larger contact patch when running skinnier tires at high pressure. This was due to the fact that my feet were touching the ground far more often.
    I think the key point for the physics is whether your training wheels are on or not???

  100. #100
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    Quote Originally Posted by skiwi
    Just discovered this thread. It is interesting that no-one has actually stated the physics first.

    1. For a given tyre pressure your contact patch size will stay the same regardless of the tyre size. Read that again. So a 2.5" tyre will have the same contact patch area as a 1.9" tyre @30psi, or @25psi or whatever.
    2. What will change with changing tyre size is the shape of the contact patch. The wider the tyre, the shorter and fatter the contact patch. But the size will stay the same.
    3. With the changing shape of the contact patch, the dynamics of the tyre will change in the 4 axis that a tyre works on (the "friction circle") - front and rear for traction/braking, and side-to-side for cornering.
    4. Generally speaking chose a narrow long contact patch for better traction & braking, and a wide short patch for cornering.

    That is the physics.

    What is also true, as someone has stated is that at lower pressures a tyre will deform to absorb a small obstacle where a tyre at higher pressure will resist deformation and ride up over the obstacle. Whether this is a "good thing" depends on the terrain, the speed and your objective.

    At one extreme, hard-packed surfaces, you work to present the smallest contact patch that you can. Using smaller tyres and higher pressures. There will be nothing faster. That is why roadies run 19c tyres @130psi for races.

    For other terrain, you need to balance speed, traction, cornering and braking to find the right combination to go fastest. This will be a combination of tyre size, pressure and tread pattern. There is no hard-and-fast rule here. You will find some tyres will be faster at higher pressure than other tyres run at lower pressure when sense says they shouldn't be. Why? Because the tyre manufacturer has developed a casing optimised for the conditions you are riding, and the tyres are fast.

    For this reason, I work on tread/compound first, size second, then pressures third.

    However, I have about 20 tyres in the garage and 3 sets of wheels setup. One with a general XC tyre-set, another with a more radical XC race set, and one with a wide software "traction" set for wet weather.
    Mfg have released snippets of their research over the years which are counter intuitive to the “Physics” as we thought we understood it. XC World Cup podium finishers using 2.4 tires have a little more info at their fingertips than we do.

    When comparing different width tires it's not the size of the contact patch which governs rolling resistance but the shape. It’s related to hysterisis not friction.

    When considering construction of tires and their rolling resistance the physical tread blocks have an affect but are secondary to the underlying tread region of the casing.

    Whether on or off road, there is trend towards wider tires having less rolling resistance. Aerodynamics aside, a 25mm road tire, even at 120 psi, has been shown to have 40% less rolling resistance than 19 mm road tire at the same pressure. A 1.7" tire at 60 psi has the same rolling resistance as a 2.4" tire at 30 psi. The rougher the ground the greater the effect. As much as 50 watts can be gained on rough terrain using the 2.4" tire at 23 psi over the the 1.7" tire at 60 psi.
    Last edited by gvs_nz; 10-09-2010 at 09:54 PM.

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