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  1. #101
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    just fyi....i was involved in this thread a while ago. after plenty of riding various tire pressures on maxxis high roller 2.5 dh casing tires, i'm at 27 front and 35 rear on my dh bike. any lower and i flat. of course this is one rocky terrain which is at my local bike park. traction and rolling resistance don't mean anything if your ride gets delayed because of flats. a recent trip to downieville showed me i'm right on with my pressures because i didn't have to stop and fix flats like other guys in our group (i ran 28/36 just in case) - it makes a run much more fun when you don't have to fix your bike half way thru it! just sayin'....

  2. #102
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    Quote Originally Posted by mr.niles
    just fyi....i was involved in this thread a while ago. after plenty of riding various tire pressures on maxxis high roller 2.5 dh casing tires, i'm at 27 front and 35 rear on my dh bike. any lower and i flat. of course this is one rocky terrain which is at my local bike park. traction and rolling resistance don't mean anything if your ride gets delayed because of flats. a recent trip to downieville showed me i'm right on with my pressures because i didn't have to stop and fix flats like other guys in our group (i ran 28/36 just in case) - it makes a run much more fun when you don't have to fix your bike half way thru it! just sayin'....
    And if the title of this thread wasn't "Tire pressure for all around XC riding", that would be a good point
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  3. #103
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    Quote Originally Posted by gvs_nz
    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.
    I'd be interested in having a look at this research. Do you have any of it?

    Also, for your example of a road tyre, there are no tread blocks to complicate factors. There is certainly compound and construction - which are significant variables - witness pro motorsport. But you can't beat the physics.

  4. #104
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    I'm 230 lbs and run 45 psi rigid or suspension and I never get flats. You should not get flats when you ride. I see so many posts about running 20ish psi and you they always get flats - like it's accepted or something. Yeah, it's a little rougher - my god you're on a MOUNTAIN BIKE. I tried 40 psi the other day and that was ok but I really like to the tight feel of a properly enflated tire.

  5. #105
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    I vary my pressure with the trail and the gang I am with. When I go on trails with very technical climbs and a bunch of good riders I tend to go as low as I think is safe and go 2 psi lower

    I usually do well clearing technical stuff while other sometimes get stumped on a slippery steep uphill section. I'd rather have to fix a flat sometime during the ride but be the only one to clear a tough section cause I was the only one with traction

    I do this cause they usually smoke me when its fast (doh)

    I'm around 140lbs, on FS 30lb GT, Running Nevs 2.1 @ 22-25psi with tubes for fun technical group rides.

    Cheers,
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  6. #106
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    I was running 50/50 for years on 2.1 tires front and rear. I swapped over to a 2.35 front and dropped psi to 35 front and 45 rear. There's a bit more rolling resistance, really feel it on the ascents but there's also much more bite on the descents and overall I'm pretty happy with the lower psi.

  7. #107
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    Quote Originally Posted by Rum Runner
    I vary my pressure with the trail and the gang I am with. When I go on trails with very technical climbs and a bunch of good riders I tend to go as low as I think is safe and go 2 psi lower

    I usually do well clearing technical stuff while other sometimes get stumped on a slippery steep uphill section. I'd rather have to fix a flat sometime during the ride but be the only one to clear a tough section cause I was the only one with traction

    Cleaning steep techy climbs is under-appreciated by too many riders. I mean, anybody can ride downhill (though some may need to go slower than others). But you make a tough climb, and you know you accomplished something.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  8. #108
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    Quote Originally Posted by trailville

    Cleaning steep techy climbs is under-appreciated by too many riders. I mean, anybody can ride downhill (though some may need to go slower than others). But you make a tough climb, and you know you accomplished something.
    I agree, going fast down is simply a matter of having a less risk perception to what your doing where as climbing is a partial skill.

  9. #109
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    OK- dumb pressure question, tire selection aside and assuming same tires, same trails, same bike-
    As things get drier and looser on the surface on your usual trails, especially sandy soil riders, do most increase or decrease pressure to gain more traction? What about increased foliage, esp pine needles(aka slippery bastards)?

    I can make a theoretical argument both ways in my head, but it's quite empty in there

  10. #110
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    repeat post

    wouldn't is be nice to be able to delete a post that isn't in the right place in a thread?

  11. #111
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    Quote Originally Posted by Noclutch
    OK- dumb pressure question, tire selection aside and assuming same tires, same trails, same bike-
    As things get drier and looser on the surface on your usual trails, especially sandy soil riders, do most increase or decrease pressure to gain more traction? What about increased foliage, esp pine needles(aka slippery bastards)?

    I can make a theoretical argument both ways in my head, but it's quite empty in there
    General rule is to lose pressure. As you release air, the tyre footprint increases and the bigger contact patch will float more over the loose stuff. Only exception to this rule is for deep mud when the ability to cut through the mud helps traction (hence narrow tyres with sharp knobs).

  12. #112
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    Quote Originally Posted by mtb63
    I'm 230 lbs and run 45 psi rigid or suspension and I never get flats. You should not get flats when you ride. I see so many posts about running 20ish psi and you they always get flats - like it's accepted or something. Yeah, it's a little rougher - my god you're on a MOUNTAIN BIKE. I tried 40 psi the other day and that was ok but I really like to the tight feel of a properly enflated tire.
    With your weight, you must use higher pressures. However, you lose traction with the higher pressures as your contact patch is smaller. Not a big issue downhill (might even help), but uphill, it's not good. In XC also generally slower. However there is a point when you need to add air to go faster....

  13. #113
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    About the "time to leave 1994" comment, many of us are still riding that way -- on a 26" hardtail.

    Currently I'm running 35f 40r on 2.1/1.9" tires. This feels pretty good all around, including the 8-12 road miles each way to/from the trails. If I go lower, I get pinch flats in the rear and the front slips around the rim under braking, threatening to shear off the valve stem.

    Next tires will be 2.2 or 2.4 for sure, now that we can get fast tires in that size (Ralphs, Saguaros, etc.) If they slip I'll glue 'em on, but probably not go tubeless as that's still too fussy for me.

    In the early 90s, Specialized made a 2.5" Ground Control, which we all thought were the cat's pajamas and surely the Next Big Thing. But most riders believed that skinny/light = fast, and few frames could accommodate these tires so they were a non-starter in the marketplace. Same with Ritchey's 2.3" Zmax, and I think Fisher made a 2.5" tire too. The cool kids at the time wouldn't be caught dead on them.

  14. #114
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    Since this thread is about XC pressure and not rocks/technical stuff, I have a ? for you FAST XC guys out there.

    My friends and I that are pretty quick on the trails can NOT run lower pressure than about 30psi in the front without rolling the front tire. The rear does the same at close to the same pressure. Now when I go on a road trip out west in the rock then I run ~24psi no problem. But I'm talking about fast single track that is pretty hard packed and cornering FAST.

    Now I know that there are lots of variables to consider like rim width, tire casing stiffness, size of tire (especially compared to rim width)....etc. I am currently running 819's with a WTB Weirwolf 2.3 UST on the front, Maxxis Advantage LUST 2.1 in the rear. Same results with a few other tires as well. Results are the same with either tubes or UST.

    So I would like to hear input on guys who can truly corner fast on more hard packed trails. What tire sizes, rim width, and finally what pressure. I you don't know exactly what I mean about the tire rolling then you aren't cornering fast enough to understand.

    thx
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  15. #115
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    Quote Originally Posted by bquinn
    Since this thread is about XC pressure and not rocks/technical stuff, I have a ? for you FAST XC guys out there.
    Since when is rocks/techy stuff not XC?

    Quote Originally Posted by bquinn
    I you don't know exactly what I mean about the tire rolling then you aren't cornering fast enough to understand.
    Good one. Most of my riding is on slower techy singletrack, but if I'm riding somewhere that I know has faster track with turns I'll up the pressure just for that reason (the squirrely feeling you get when your front tire rolls sideways). Every bike setup decision you make is some type of compromise. But it is different for different tires.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  16. #116
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    Holy God, you guys run some high pressures...

    I went on a quest to find the fastest rolling tires possible, and first went with Small Block 8's, then tried Gaex Sagauros - which I have both on my 26" and 29'er rigids. Both fanatastic tires and mounted up tubeless with ZERO problems - no burping, even on incredibly rocky terrain - I believe I have 2.35's on both bikes. I ride the trails 5-7 days a week, and I ride to the trails (none of that driving garbage). Sometimes I'll cover 20 miles+ of asphalt on my mountain bike if I want to go explore more.

    I am 210-215lbs and I run 22-26 psi most of the time, usually higher in the rear tire. Before I leave the house, I start at 30psi, and adjust at when I get to the trail. If it's hardpacked and smooth - there's no need for adjustment. When I check it after the ride, I will find I am down to the 22-26 range in most cases.

    On my tubeless 'cross bike, I change the tire pressure depending on the course, but I start at 40psi and go down from there. 'Cross racing is a whole different beast.

    I pretty much ride XC most of the time, but I do throw in the technical stuff almost every ride. Climbing rocks I can definetely feel the difference when I have too high of pressure. Doesn't affect my XC riding, either: whatever that means, but it looks like my rock climbing doesn't including fast XC. Again, I think I found the fastest rolling tires for my trails.

    IMO, it's hard to get a true answer for your situation. I think talking to the local racers in your neck of the woods and asking them their set-up would be the best direction to go, or ask your LBS what the sweet set-up is. IMO, it's very regional specific. I bet my set-up would suck for more humid areas like Florida and in the South. For Nor-Cal, my set-up works like a charm.

  17. #117
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    Quote Originally Posted by Dion
    IMO, it's hard to get a true answer for your situation. I think talking to the local racers in your neck of the woods and asking them their set-up would be the best direction to go, or ask your LBS what the sweet set-up is. IMO, it's very regional specific. I bet my set-up would suck for more humid areas like Florida and in the South. For Nor-Cal, my set-up works like a charm.
    This is a great point Dion. XC means so many different types of terrain depending on the area of the country you live in. I for one have no rocks, no steep technical climbs, just fast single track in the woods that can be very hard packed (sometimes completely solid if it's been dry like all fall here). For that circumstance I can't imagine running mid to low 20's while cornering fast if my tires start rolling at ~29-30lbs.

    My LBS which has some well qualified riders, including the owner which has mounds of race trophies on his walls can't run less than 32lbs or he runs into the rolling issue. Another rider is at 45lbs F/R and neither understand how it would be possible to run the low #'s. I'm sure there are other riders on this board that have hard packed single track and run into this issue and was hoping with some time I would hear from them.

    I didn't mean to be snotty about the 'actually fast' comments, but I've learned over time that many riders that claim to be fast are far from it when cornering, and I need experience/comments from those that truly are.

    thx
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  18. #118
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    Quote Originally Posted by Dion
    Holy God, you guys run some high pressures...

    I went on a quest to find the fastest rolling tires possible, and first went with Small Block 8's, then tried Gaex Sagauros - which I have both on my 26" and 29'er rigids. Both fanatastic tires and mounted up tubeless with ZERO problems - no burping, even on incredibly rocky terrain - I believe I have 2.35's on both bikes. I ride the trails 5-7 days a week, and I ride to the trails (none of that driving garbage). Sometimes I'll cover 20 miles+ of asphalt on my mountain bike if I want to go explore more.

    I am 210-215lbs and I run 22-26 psi most of the time, usually higher in the rear tire. Before I leave the house, I start at 30psi, and adjust at when I get to the trail. If it's hardpacked and smooth - there's no need for adjustment. When I check it after the ride, I will find I am down to the 22-26 range in most cases.

    On my tubeless 'cross bike, I change the tire pressure depending on the course, but I start at 40psi and go down from there. 'Cross racing is a whole different beast.

    I pretty much ride XC most of the time, but I do throw in the technical stuff almost every ride. Climbing rocks I can definetely feel the difference when I have too high of pressure. Doesn't affect my XC riding, either: whatever that means, but it looks like my rock climbing doesn't including fast XC. Again, I think I found the fastest rolling tires for my trails.

    IMO, it's hard to get a true answer for your situation. I think talking to the local racers in your neck of the woods and asking them their set-up would be the best direction to go, or ask your LBS what the sweet set-up is. IMO, it's very regional specific. I bet my set-up would suck for more humid areas like Florida and in the South. For Nor-Cal, my set-up works like a charm.
    Certainly for your type of riding, in fast hard-pack conditions hich pressure is the way to go. Just like road riding, small contact patches are fast when traction is not an issue. I assume that you use low-knob tyres as well? Furious Fred or Small Block8?

  19. #119
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    You must be really fast to roll your tire off your rim on single track with 30 psi. Check the downhill threads and guys are generally running same or lower pressure than you. Or is it just you do night like the feel of the tire squirming?

  20. #120
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    Quote Originally Posted by skiwi
    Certainly for your type of riding, in fast hard-pack conditions hich pressure is the way to go. Just like road riding, small contact patches are fast when traction is not an issue. I assume that you use low-knob tyres as well? Furious Fred or Small Block8?
    I ride Gaex Sagauros on both my 26" and 29er. I ride both bikes rigid and it is very, VERY bumpy and rocky on the trails I ride daily. Baseball sized rocks that will shake a dental filling loose. If it was smoother, I probably would run a bit of a higher pressure - like today I'm riding in Santa Cruz and will inflate my tires a bit.

    Believe-you-me, I've spent a lot of money and fiddling around with tire pressures with lots of different tires and lower pressure/fast rolling small knobs works great for me.

    I doubt it would work as well in other parts of the country, though.

    I run higher pressures on my 'cross bike when I train for racing, understanding I'm not going to be riding on MTB trails and I need a little more speed.

  21. #121
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    I agree it's a personal thing. I use 60psi and roll a lot faster then my friends. In fact, I cost past them while there pedaling.

    Chris.

  22. #122
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    Quote Originally Posted by happydog500
    I agree it's a personal thing. I use 60psi and roll a lot faster then my friends. In fact, I cost past them while there pedaling.

    Chris.
    And how does 60psi work on Devils Gulch? Still faster than your buddies? Able to stay on the trail?
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  23. #123
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    Works supper good!! Twice I hit hard but its fast coming down!! If you go up the gulch (actual trail, not mission creak) you'll spin in a couple areas, but other then that its fast.

    Chris.

  24. #124
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    Quote Originally Posted by happydog500
    I agree it's a personal thing. I use 60psi and roll a lot faster then my friends. In fact, I cost past them while there pedaling.

    Chris.
    You gotta be trolling for a bite. You got one.

    Is this based on experience through using large volume tires at lower pressure and then reverting back to skinny tires at roadie pressures? Coasting at high speed on smooth surfaces has a lot, if more, to do with aerodynamics.

    I can say the same thing about about coasting down trails while on race kings behind guys on skinny tires at ridiculous pressures bouncing all over the place.
    Take a look at some of the current[ not 1990]world cup vids and see if you can see anybody on skinny tires at high pressure. Some are running 2.4's and they are big 2.4's.

    Xmas is coming, do your joints and back a favour by buying a Race king 2.2 and set it just above squirm pressure and feel what smooth speed is, not perceived speed. Do back to back timed tests with your current set up then post back to us. I'd be very surprised if you still stuck to your current set up.

  25. #125
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    60psi, Wow.
    I don't even run 60psi in my 700x35 cross tires on my touring bike.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  26. #126
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    I am not trolling for anything. I speak from the hart, with genuine questions. If I ride from Arlberg Sports parking lot, up twin peaks, down stairway back, I guarantee most of the ride, the rolling resistance is not "perceived" but an absolute fact that can easily, or very easily be felt (Typical for me; Mountain Bike ride, but is mostly pavement).

    Not last year, but the year before, all summer I trained on my Mountain Bike, from downtown Wenatchee, to Mission Ridge. I'd go off and do a trail ride, then back to pavement, without stopping to take air out, then to put air back in.

    I do a lot of rides where most people drive to the trail. I RIDE TO the trail, then on the trail, then back to the road. I ride a mountain bike, on the dirt, but am actually on pavement most of the time (instead of driving to trail, I ride bike).

    If I go down Devils Gulch, I ride back to Wenatchee, not drive back. Some ride up, stop, change the seat height, change air pressure, waist a bunch of time fooling around with there GPS's. Get to the rode, change air pressure, and seat height.

    My preference is to set the bike up. Ride to the trail, ride the trial, ride back without having to make a bunch of adjustments.

    I did change pressure down Freund Canyon last year. With the heat from braking the pressure was a little high for the jumps on the downside.

    I think the difference is that most who ride the dirt, that day just ride dirt. My dirt rides are mostly pavement. So where not really compairing the same thing when I say I ride with 60psi 'on the dirt.'

    Chris.

  27. #127
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    Quote Originally Posted by trailville
    60psi, Wow.
    I don't even run 60psi in my 700x35 cross tires on my touring bike.
    Why not? You'll roll a lot faster.
    Dad worked in the tire business for 50 years. I've gone out on a ride and wondered what was going on, since it is such a drag. Are my breaks rubbing? Check and see that tires had leaked to 40psi. Not sure why some would think a tire with more pressure doesn't roll faster, with less resistance. I can very easily feel (not perceived) a huge difference in rolling resistance, with high pressure.

    Chris.

  28. #128
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    Quote Originally Posted by happydog500
    Why not? You'll roll a lot faster.
    Dad worked in the tire business for 50 years. I've gone out on a ride and wondered what was going on, since it is such a drag. Are my breaks rubbing? Check and see that tires had leaked to 40psi. Not sure why some would think a tire with more pressure doesn't roll faster, with less resistance. I can very easily feel (not perceived) a huge difference in rolling resistance, with high pressure.
    I believe there was some kind of a study recently that showed that rolling resistance relative to tire pressure changed once you left the flat smooth surfaces behind. But even without that, I simply prefer traction, control, and comfort over rolling resistance. I'd rather clear a technical section or make a really tough techy climb than roll fast on the easy sections. Everyone has their own preferences.
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  29. #129
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    I like to clear a technical section, and really though techy climbs with higher pressure. I'll mix it up and try a little lower pressure on one of the next trail rides. I gotta hurry because it's getting pretty cold around here now.

    Chris.

  30. #130
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    Quote Originally Posted by happydog500
    Why not? You'll roll a lot faster.
    Dad worked in the tire business for 50 years. I've gone out on a ride and wondered what was going on, since it is such a drag. Are my breaks rubbing? Check and see that tires had leaked to 40psi. Not sure why some would think a tire with more pressure doesn't roll faster, with less resistance. I can very easily feel (not perceived) a huge difference in rolling resistance, with high pressure.

    Chris.
    Here's some info for you to give you confidence to try a larger volume fast rolling tire at low pressure. Many have switched over and like it. Like plenty before you,it pays to read all of a thread not just the last posts.

    http://www.schwalbe.co.uk/pdf/techinfo.pdf pages 14 to 16
    Attached Files Attached Files
    Last edited by gvs_nz; 11-17-2010 at 01:24 PM.

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    Thank you for the link. I love to read stuff like this.

    Chris.

  32. #132
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    Don't know your weight but 60PSI may be right for a skinny 2.1 tire under a 300 pound rider.

    You'll be amazed at what you can clean on a slow technical climb by using a fat (2.5) front tire at low pressure. It works even better on technical descents. A real confidence builder. Most people are amazed at the difference a fat low pressure front tire makes.

    However, if most of your riding is smooth hardpack, then all that big tires do is slow you down.

  33. #133
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    Love my HUGE Volume RQ2.4 so much, I've got a 3" Arrow Savage coming heavy but should gobble rock gardens which I need help with, like there not there on the rigid to

  34. #134
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    I run 35 psi front and rear for everything, and i have a 2.4 front and a 2.25 rear its good on the trail or street and i run with tubes

  35. #135
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    This is something that came up the other day when my buddy just bought his first Full Suspension bike (Trek Fuel EX5). We are here in the Tampa Area and I asked the Trek Rep to check the tire pressure out the door and adjust it for one of the locations we hit (Alafia State Park). He said he runs them at 40psi. I thought that was awfully high since I run my Stumpy FSR 29 at about 28 front and back, he thought that was awfully low. I weigh in about 240lbs and I feel pretty fast on the trail at that pressure although I may try a higher pressure just for the comparison. I havent gotten a flat since I moved the pressure above 25.
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  36. #136
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    60 front/ 70 rear....

    Quote Originally Posted by trailville
    60psi, Wow.
    I don't even run 60psi in my 700x35 cross tires on my touring bike.
    on the pump track, 2.1 small block 8's, 165lb rider, hardtail.

    trailville: saw your comment about this being a xc thread - when did this become strictly a xc thread?? xc can cover a broad range of riding on a broad range of terrain. that's what's been good about this thread, there's a lot of specific info here that may be helpful for what certain riders are looking for.

    sometimes higher pressure works very, very well.

  37. #137
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    1 rather major thing to remember here people :-


    PRESSURE GUAGES DON'T WORK!!!

    The 60 is likely really 40's area, and the 22's are likely 30's area.


    Try a few marvel at how your mates give a totally different reading to your own.


    Some tires, you need higher pressure to keep the knobs out to get traction, RK2.2's are like this, run them to soft and they become full on slicks and yes they'll role faster but there slicks nothing more.

  38. #138
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    Quote Originally Posted by mr.niles
    trailville: saw your comment about this being a xc thread - when did this become strictly a xc thread??
    When the OP posted it as "Tire pressure for all around XC riding" . But it's not like this would be the first thread to run a little off the initial topic.
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  39. #139
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    yes, a good gage is necessary....

    Quote Originally Posted by Turveyd
    1 rather major thing to remember here people :-


    PRESSURE GUAGES DON'T WORK!!!

    The 60 is likely really 40's area, and the 22's are likely 30's area.


    Try a few marvel at how your mates give a totally different reading to your own.
    .........
    never trust the gage on your pump - it is almost surely wrong. use it as a guideline to overinflate your tires before using a proper gage to bleed down to your target pressures. get an accurate gage from mcmaster-carr or a motorcycle shop, etc. the only problem with these gages is no chuck for presta valves. to get accurate pressures while using a good gage, i've had to convert all my tires to shrader. i don't recommend using those little brass presta-to-shrader converters.

    my buddies like to use my gage when we ride together, because we all trust it.

  40. #140
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    Tire pressure for all around XC riding?-img_1406-1-2-.jpg How much sag should your high volume tire show under rider weight when using lower tire pressure? This seems pretty soft what I have here in these tires and shows some tire sag with my 155 lbs. When squeezing the tire is feels pretty soft. Running Forte Lunar light tubes. I don't have a decent tire guage.
    Last edited by ancient rascal; 05-23-2011 at 06:51 AM.
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  41. #141
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    As others have said, get a tire gauge. Visual "sag" of the tires doesn't give you very much information IMHO as there is so much variability in sidewall stiffness amongst different tires. You need to experiment with tire pressures in different conditions to find out what works best for you.

  42. #142
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    Quote Originally Posted by ancient rascal
    Click image for larger version. 

Name:	img_1406-1 (2).jpg 
Views:	1247 
Size:	300.8 KB 
ID:	615687 How much sag should your high volume tire show under rider weight when using lower tire pressure? This seems pretty soft what I have here in these tires and shows some tire sag with my 155 lbs. When squeezing the tire is feels pretty soft. Running Forte Lunar light tubes. I don't have a decent tire guage.
    Good question. From your picture, one cannot definitely identify substantial sag. You tire really feels pretty soft?
    I tried the same with my bikes. The first has Mythos XC II and the second Fat Albert tires. To investigate the sag, I took pictures when sitting on my bike (i.e. sag) and when the bike unloaded (i.e. no sag). You can clearly see that there is sag under rider weight (165 lbs).
    Note that the tire pressures were carefully adjusted by a mountainbike tire pressure specialist. He knows how to account for the individual aspects of the tires, the bike and its rider.
    Attached Thumbnails Attached Thumbnails Tire pressure for all around XC riding?-fat-albert-loaded_01.jpg  

    Tire pressure for all around XC riding?-fat-albert-unloaded_01.jpg  

    Tire pressure for all around XC riding?-mythos-xc-ii-loaded_01.jpg  

    Tire pressure for all around XC riding?-mythos-xc-ii-unloaded_01.jpg  


  43. #143
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    Quote Originally Posted by xc-biker View Post
    Good question. From your picture, one cannot definitely identify substantial sag. You tire really feels pretty soft?
    I tried the same with my bikes. The first has Mythos XC II and the second Fat Albert tires. To investigate the sag, I took pictures when sitting on my bike (i.e. sag) and when the bike unloaded (i.e. no sag). You can clearly see that there is sag under rider weight (165 lbs).
    Note that the tire pressures were carefully adjusted by a mountainbike tire pressure specialist. He knows how to account for the individual aspects of the tires, the bike and its rider.
    Prolly need to use a few methods to get it close. Hand squeeze. tire gauge. And just a thought. A sag gauge. Have a weight set up to enforce a sag on said wheel on a rigid floor. Have a means to measure the inside part of the rim to the floor measuring sag. Once you find your ideal tire pressure you can get back to it with the sag factor. Example floor to inside top of rim aprox 3 inches or whatever it is. Horseshoe type gauge over bottom of rim. Bet it gets it pretty close. It's OK to let me have it on this.....I can take it !
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  44. #144
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    While I am no racer, I do ride single track and am close to 300#. I prefer 30 psi in my Sepcialized Fastrack tires front and rear. Anything more and I can't find traction when I need it on climbs and roots.

  45. #145
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    I'm 190 pounds plus gear and I'm riding conti Xking 2.2 FR/RR on flow rims. Running 18psi (according to my pump) front and 23psi rear lately and am very happy. Not many large sharp edges to worry about in my local trails. I'd up the pressure a bit if riding rougher trails at speed but only as much as is necessary. The traction and control of "softer" tires is awsome! Really helps keep the bike planted.

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    I am runing Botrager XDX, tubeless. Run 18 front 20 rear, and it's ok for grip and bump absorbtion, no rim contact, but if you end up jack knifing the front you will pop the tire of the rim, or loose air presure.
    25 front and 30 rear doesn't soak up the bumps as good (you feel more of the terrain) but the tire stays put

  47. #147
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    I've posted last year in this thread and was running 2.1 Nevs. Had a ton of flats last year. Running tubes.

    This year I switched tires and am running a 1.95 Nev (150g lighter than 2.1) front and my Karma rear (under 400g which is around 280g lighter than the rear Nev 2.1 it replaced).
    Pressure for several XC races has been 27 psi front and 29 psi rear with no flats(tubed) (knock on wood!!!)
    Traction has been better than I anticipated with a couple of wet races and our local race at Camp Fortune is extremely gnarly, rocky and rough
    Doing an Ultimate XC race on 19th of June, 100 kms of crazy single track and 10,000 - 12,000 feet of climbing from what I read on this tire combo so will be a good test

    Cheers,
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    So a quick report on the UltimateXC 100km race.
    Managed to finish in 10 hr and 40 mins with one flat and one slight mechanical.
    I was running the 1.95 Nev F @ 27 psi and 2.0 Karma R @ 29 psi.
    Where I flatted several other riders flatted. It was a rough fast downhill section.
    99 % f the trails were dry or mildly moist. It consisted of soft loamy forest floor to rooty to gravel to Canadian shield solid rock. Were a couple short sections of maybe 50 feet of swamp black mud, bit clayish.
    I had super traction except the clay part and a few fast downhills with smallish type gravel.
    There were a lot of STEEP sections and the tires had more traction than I had power left haha.
    Two gravel climbs of 1 hr each of relentless no stop UP, no plateaus, of 8-25% section of 1600 ft and 1900 ft with 1-2 inch gravel. Was pretty loose stuff but still was gripping well with minimal slippage. Some of the downhill sections after those climbs were insane! ! ! Switchback after switchback hard on the both brakes feathering front brake to not go over bars ! !
    In retrospect I am super happy with these tires in any type of dry conditions and non clay type mud. OK on wet roots from other rides.
    So for me on my 4" FS GT @ 28ish lbs and me around 135 lbs the 27-29 psi worked really well. I rode just about every type of dry conditions... Sand, tall grass, Loamy forest, rooty forest, big/small gravel, rock, dirt .....
    Was a section at finish as we zig zagged downhill through the village on pavement and cobblestones that I was just ripping through and the tires felt super solid with no feeling of the tire wanting to roll on the rim. I felt like I was rolling on the road bike !
    Cheers,
    Paul

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  51. #151
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    Ive kept mine at about 28 front and about 26 back....that seems to work fairly well for me right now. I run tubes and still no issues...but I have tried a gamut of pressures and noticed the higher pressures (at least for me and my trails) tended to slow me down...alot, and backing them off gave me more speed and maneuverability....so my recommendation is to try some variations out for yourself and see what you like
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  52. #152
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    Psi

    I just got back from a 3 hour ride. Conditions were stilla bit muddy with tons of damp rocks a wet roots....i run 35 psi in front on geax Saguaro 2.0 and 35 rear michelin gravel country 1.95....the runs were a bit slippery but still ok

  53. #153
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    i run 52psi on 2.2's and i am 175 on short travel fully

  54. #154
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    45 psi... or I will start to flat too much. 210 lbs

  55. #155
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    Schwalbe RR+ Stan's- Pressure Q for mixed riding

    After reading this thread, I switched out my tires for Schwalbe Racing Ralph 2.25 SS rear and 2.1 front, with Stan's on the rims. First time going tubeless.

    I'm looking for tire pressure suggestions for overnight adventure racing with these.
    We'll hit dirt roads, ATV trails with deep muck-holes, rocky Canadian Shield, unrideable swamps and decent doubletrack. Probably no twisty purpose-built singletrack.

    I'm a light guy at 150lbs but my bike's got a lot of rear weight bias, and I'm carrying a lot of gear, much on a rear rack (Long story). I've raced this way for years, with 40PSI in a Hutch Python 2.25 on the rear and a Bonty Revolt-X 2.0 on the front with 30PS!.

    I'd appreciate pressure suggestions for the new tubeless setup. I know harder tires would be better for the dirt roads, but I'd lose more time if I can't make it over the nasty bits or if I get flats.

    Thanks in advance.

  56. #156
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    Quote Originally Posted by Wanny View Post
    45 psi... or I will start to flat too much. 210 lbs
    weird, im 220~ geared up and I run 33-35 front and rear and haven't pinched flatted yet, when I was at 29 and 30 I did all the time.

  57. #157
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    I need two more posts so I can start a new thread in "Wheels and Tires", thats where this belongs.

    Ever mount your tubeless tires and get a bit of a wobble because the tire is not perfectly aligned on the rim?

    How important is it for the tire to roll true?

    I had a small wobble once on the rear tire but not bad and it held air just fine. I had a bike shop mount my last pair of tires when I purchsed new tires. One tire wobbled noticeably and hasn't held air very well. I will remount it but I was wondering if there are some tips for getting the tires true to the rims when mounting tubeless tires. BTW- Using Stans sealant, works great otherwise. ALSO, IT'S A SIDE TO SIDE WOBBLE.
    The bike is a 2008 stumpy w/ Specialized Captain tires. Rims are Specialized brand and are true.

  58. #158
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    Second post. Yea!

  59. #159
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    Quote Originally Posted by gvs_nz View Post
    Here's some info for you to give you confidence to try a larger volume fast rolling tire at low pressure. Many have switched over and like it. Like plenty before you,it pays to read all of a thread not just the last posts.

    http://www.schwalbe.co.uk/pdf/techinfo.pdf pages 14 to 16
    Outstanding paper. For the lazy, here is a quick summary:
    Quote Originally Posted by Schwalbe
    Off-road rolling resistance decreases significantly with increased tyre width. For instance on grass the wide mountain bike tyres required 15.41 W less rolling resistance power than their narrower equivalents.
    Quote Originally Posted by Schwalbe
    Off-road a reduction of tyre pressure reduces rolling resistance. In a meadow for instance going back from 4.0 to 1.5 bar (57 to 21 psi) can save remarkable 18 Watts of power.
    Quote Originally Posted by Schwalbe
    FIRMLY inflated narrow tyres are history. 'Fat' and less air speed things up!
    On the road it's the opposite.

    As for me, as low as the tire does not squirm. I can't get myself to slam the wheels into rocks to see how low you can go without a flat.

  60. #160
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    My pinch-flat-free streak is over.

    Quote Originally Posted by trailville View Post
    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.
    Well, I can't say this anymore. After 2 decades of riding without ever getting a pinch flat and having run pretty low psi for at least the last 5 or so years, it finally happened. I was heading out for a quick trail ride on my rigid SS this afternoon, and though I normally put 24-25 in a rear 2.1 tire, my gauge read 23.5 and I thought "that's fine". Well, immediately after hitting a crude rock bridge (basically a line of larger rocks across a shallow creak), I heard the air whoosh out and knew my luck had finally run out. To make things worse, since this was just intended to be a quick ride, I didn't bring a spare inner tube as I normally do, and, of course, my unopened tube of rubber cement in my patch kit was empty when I perfed the top (I've had that happen before with old patch kits). So I got to walk.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  61. #161
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    I have 2.2 mountain kings and when running28-30psi pinch flat almost every trail ride. my weight is 180. I started running 35psi and no pinch flats. So tailer the psi to trail and you.

  62. #162
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    If there is such a thing as an exact science to tire pressure for offroad bike riding then we wouldn't be having these threads all over the net. I read somewhere that the proper pressure should be when the sag is 15%, then what about those tires that use softer compounds? Would the 40% front 60% rear times your body weight formula work in all applications? Is it faster to have a wide tire with low knobs ran at low press rather than the usual narrow high press? Are you really faster overall by having a tire that's fast and slippery rather than a heavier one that grips?

    There's no right and wrong. It all depends on the particular trail you're riding, your riding style, and your body weight. I too had spent too much on tires experimenting different types. Sometimes sold them after 1 ride. Unlike in US, all of my tracks involve all kinds of conditions including mud. Now I just ran Nobby Nic Pace Stars 2.1 which has the awesome grip due to soft knobs yet lighter than anything else in the market. I just play with the PSI for the different conditions. Sure soft compounds wouldn't last that long and will cost more $ in the long run but I get both safety, comfort and speed in all conditions.
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  63. #163
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    Quote Originally Posted by mr.niles View Post
    just fyi....i was involved in this thread a while ago. after plenty of riding various tire pressures on maxxis high roller 2.5 dh casing tires, i'm at 27 front and 35 rear on my dh bike. any lower and i flat.
    Your point being that because of lower pressure you're slower not due to higher rolling resistance or difficulty pedaling but because of flats. But that should be out of the question if you're running tubeless which also means you can run even lower pressure. Go tubeless bro!
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  64. #164
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    Interesting thread guys ... I have always run high pressures in my tire 'cause I'm a big guy who doesn't like to repair flats. I'm 105kg (231 lbs) and running a 2.5 Weirwolf up front and a 2.4 Motoraptor on the real of my old '95 Avalanche. I had 45 psi in them yesterday and I notice they were a little bouncy so I'll drop 'em to 35 psi and take my friends Mr tire pump and Mr accurate pressure gauge on my next ride.
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  65. #165
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    Quote Originally Posted by the old fool View Post
    Interesting thread guys ... I have always run high pressures in my tire 'cause I'm a big guy who doesn't like to repair flats. I'm 105kg (231 lbs) and running a 2.5 Weirwolf up front and a 2.4 Motoraptor on the real of my old '95 Avalanche. I had 45 psi in them yesterday and I notice they were a little bouncy so I'll drop 'em to 35 psi and take my friends Mr tire pump and Mr accurate pressure gauge on my next ride.
    You do get more flats in low pressure, but you don't get flats running tubeless

  66. #166
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    Well if i have to go tubeless I might just have to get a new bike !
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  67. #167
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    Quote Originally Posted by the old fool View Post
    Interesting thread guys ... I have always run high pressures in my tire 'cause I'm a big guy who doesn't like to repair flats. I'm 105kg (231 lbs) and running a 2.5 Weirwolf up front and a 2.4 Motoraptor on the real of my old '95 Avalanche. I had 45 psi in them yesterday and I notice they were a little bouncy so I'll drop 'em to 35 psi and take my friends Mr tire pump and Mr accurate pressure gauge on my next ride.
    Wow, I'm surprised a 2.4 Moto would even fit on the back of a '95 Avalanche.
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  68. #168
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    Quote Originally Posted by the old fool View Post
    Well if i have to go tubeless I might just have to get a new bike !
    It's not that bad. Stan's conversion kit works, its much cheaper than a new bike.

  69. #169
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    low pressure is better

    I will have a look at Stan's thanks

    I found 35 psi had an amazing effect on my ride, the bike rolled well stuck to the ground better and my hands didn't get such a beating

    So I dropped the pressure to 30 psi and it's even better ...

    Thanks for the advice
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  70. #170
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    Quote Originally Posted by Veda View Post
    Your point being that because of lower pressure you're slower not due to higher rolling resistance or difficulty pedaling but because of flats. But that should be out of the question if you're running tubeless which also means you can run even lower pressure. Go tubeless bro!
    yes, doing tubeless this dh season. works very good, but can't lower the pressures much without hitting the rim - there's al;ways that one damn rock that's the perfect shape in the place where you really want to ride to bonk your rim on.

  71. #171
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    Quote Originally Posted by mr.niles View Post
    yes, doing tubeless this dh season. works very good, but can't lower the pressures much without hitting the rim - there's al;ways that one damn rock that's the perfect shape in the place where you really want to ride to bonk your rim on.
    Yep. I run 32/34 on my 2bliss spec purgatory 2.4/2.2 tires. Always felt great, never had any flats. Until this weekend riding at Snowshoe; miss-timed a rock step-up and BAM had a rather explosive burp of the rear along with a heavy hit to the rim, shredding the rear tire.

    Don't know what I could have done differently...other than having a wider wheelset to run DH tires, or a different bike, or being a better rider and not bashing into stuff. It's not like I was running super low pressure.

  72. #172
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    Quote Originally Posted by mr.niles View Post
    yes, doing tubeless this dh season. works very good, but can't lower the pressures much without hitting the rim - there's al;ways that one damn rock that's the perfect shape in the place where you really want to ride to bonk your rim on.
    And because I'm thinking about getting a different set of tires for lift riding after this weekend, I'm curious as to what you went with. Rim width? tires? UST rims and tires? or conversion? and what pressure?

  73. #173
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    Quote Originally Posted by CrozCountry View Post
    You do get more flats in low pressure, but you don't get flats running tubeless
    Sometimes you get fewer flats because you have more control and can avoid the big pointy bits rather than sliding/bouncing into them.

    And tubeless does not guaranty you will not flat.
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  74. #174
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    Quote Originally Posted by CrozCountry View Post
    Outstanding paper. For the lazy, here is a quick summary:



    On the road it's the opposite.

    As for me, as low as the tire does not squirm. I can't get myself to slam the wheels into rocks to see how low you can go without a flat.
    Just note that they were testing wide tires at low pressure. If you run narrow tires at low pressure you may find they feel slower. Rolling resistance relates to the distortion of the casing. A narrower tire probably distorts excessively at low pressure negating any benefit from running at low pressure.

  75. #175
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    40 front + rear on my Rockhopper 29 exp.

  76. #176
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    Quote Originally Posted by ricky916 View Post
    weird, im 220~ geared up and I run 33-35 front and rear and haven't pinched flatted yet, when I was at 29 and 30 I did all the time.
    I had a talk with a buddy on the trail over the weekend and I told him I always have been at like 45 just out of the fear of pinching and the thought that it would make it roll faster on the climbing. I'm ok with the tire supposedly bouncing off of stuff because at 225 (not counting the gear) My suspension is eating up that bounce. LOL I was curious to see if other riders over 200 do the same. I had another friend on a ride a few weeks ago tell me about that study where the tire rolled better at lower pressures. Now after seeing it again I think I'm going to start lowering my pressure to see what happens. Thanks!

  77. #177
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    I always thought it was the riders choice only if it's within the tyres guidelines not to low not too high! that's what i did anyway.

  78. #178
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    I'm using 20-25 psi on my 2.25 Rocket Ron's on a 29er. I probably weigh 140 lbs with my gear.

  79. #179
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    im 230 lbs i run 36 in the front and 40~42 in the rear

  80. #180
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    Just want to know should I run tubeless? What are the pros when riding tubeless?

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    I'm glad I decided to check out this topic. I've always ran 32psi just because that was what someone had mentioned to me when I asked. I'm going to start playing around with it more to see how the ride is effected.
    Thanks!

  82. #182
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    i run 30f/35r and i weigh 195lbs

    all terrains in my area
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  83. #183
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    Quote Originally Posted by Frogfuel7 View Post
    Just want to know should I run tubeless? What are the pros when riding tubeless?
    There are plenty of other threads discussing that, this one is about pressure.

  84. #184
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    I overdid it. I had a front tire roll off the rim this weekend after a landing from a tiny jump with the front not completely straight. Just got a digital pressure gauge, and checked how much pressure I had (eyeball the front with fingers, close enough). 10-11PSI in the front, 15 in the rear. Not kidding. No more 15 PSI for me. I will miss the traction, but not miss the tire rolling off

    The tire pressure gauge is my new riding buddy.

  85. #185
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    Pulled the trigger on some tubeless near the end of the summer. Did a couple training rides and a few laps of a 24 hr solo attempt when rear suspension broke and we didn't have tools to extract a broken part.
    I was running around 23 psi front and 25 psi rear on 2.2 Mountain Kings. Tires worked great. Was almost perfect conditions so roots and rocks were pretty dry. Traction was great and tires felt like they rolled really well.
    I couldn't seal them up without sealant but I only put 1/3 scoop of Stans and still holding air after 3 months.
    I was using similar pressures in my tubed 2,1 Nevs and about 5 psi more in tubed Karmas on my very rough/rocky local course(Camp Fortune QC). Got a lot of flats this year when racing but while out trail riding only one flat as our focus is more on lower speed technical climbs and descents.
    Will update in the spring when I get a chance to do more MTB'ing. Currently in Cyclocross race mode and using road bike on the rollers.
    For fun I am runnining about 32-34 psi on Scwalbe CX Pro 700x30C with tubes and no flats two seasons

    Cheers,
    Paul

  86. #186
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    I don't know how much air I let out when I get to the trail head, whatever feels right. I started to check it when I got home. Found out 18-22 front and 24-27 rear was pretty typical. Much less than the old 1.95x26" pressures.
    Fully rigid. 2.35x29 WTB tires with tubes, Velocity Blunts. 175lbs + weight of bike.
    Every once in while I will feel the front tire bottom on the rim. No pinch flats on front yet. Have had a couple on rear long after the ride has ended.
    Trail is hardpack with river rock. Lots of sharp broken shale rock with a few roots.

  87. #187
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    Start with something like 37psi front and 40 rear.
    If you don´t get a punkture let 2psi out next time, after a fiew rides of litting air out you will fint your soft spot...

    My main advice is to ride with 2-4psi less in the front wheel.

    Cheers,
    Helgi Berg.

  88. #188
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    Im 130lbs and running Ritchey Z-max Evolutions 1.9 in the rear at 23psi and 2.1 in the front at 20psi. Running tubeless with Stans ZTR olympic rims.

  89. #189
    Texan
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    I'm 198 pounds, ride mostly hardpack. Current tires are Karmas and I run 40 up front, and 45 in the rear. I'm a 53 year old trail rider and in no hurry. If your like me, don't worry about getting exactly 16.3 psi or whatever in your tires. Tire pressure is WAY over rated for the casual rider.

  90. #190
    Cormac
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    I run 26 psi with tubeless and I'm 150lbs.
    '11 Dawes Deadeye
    '12 Niner E.M.D. 9
    '09 Giant ocr c1
    Xtracycle

  91. #191
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    60psi atras y 55 adelante

  92. #192
    Poqitas
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    Mtb pressure calculator

    It seems to be a nice pressure calculator: mtb.ubiqyou.com

  93. #193
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    Quote Originally Posted by Poqitas View Post
    It seems to be a nice pressure calculator: mtb.ubiqyou.com
    No thanks. Getting riding tips from magazine articles is how I ended up running too much pressure for far too many years. It all sounds good when you're a noob, but once you start to actually know something about mountain biking, you quickly figure out the guys that write for those magazines don't know squat.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  94. #194
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    171 pound rider, shimano xt UST rims, maxxis ardent exC/UST/LUST 26x2.25 tires on both ends, 20 psi front 22 psi rear. Any lower for me and I can feel a loss in performance. running tubeless.

  95. #195
    Poqitas
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    ...

    ...

  96. #196
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    I had mine at 15psi before , me and my bike weighs 175lbs combine , but 25 psi seems to be the winning pressure for me on Geax mezcal 2.1 w/tubes, now i just went tubeless couple days ago w/ the same tires, so I'll probably have to go up on pressure a little.

  97. #197
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    My problem with going around 15PSI was tire rolling off the rim. I am in mid twenties now. The difference for the Nevegal is that I have to lean the bike more into the turn to get the side knobs to bite, not a biggy.

  98. #198
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    I'm surprised at some of the high pressures people are running(40+ psi) for trail riding. I'm fairly new to the sport, but usually go about 35psi rear 33psi front on my hardtail and I've never had a pinch flat(knock on wood). I'd go a little lower in pressure but I am nervous of pinch flatting. I'm 205lbs and currently use 2.1" Weirwolf race tires.

  99. #199
    bay area CA
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    wow, so much discussion on tire pressure. being mostly a BMXER my whole life, ive always prefered to have my tires high pressured. i understand the benefits of aring down, i do a lot of 4-wheeling and airing down is key, but personally i hate any type of rolling resistance when im on my bike and i hate repairing flats. i get the increased traction of aired down tires and its benefits though. i did the shafter grade in bolinas twice this summer, and the second time i aired down the rear tire a bit to keep that back wheel biting up that crazy incline, but generally i like my tires to be right at 45-50 on my hardtail. call me crazy but im handling business out on the trail, so i guess it comes down to each rider experimenting and finding whats feels right for the type of rider they are.

  100. #200
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    Since buying a AM bike with 160mm suspension I have really been pushing the speed when going downhill to limits never reached before (to my experience at least) and therefore having a good tyre set up has become more important than ever for me as loosing grip at speed has already proven to be very painful.

    Traditionally, when riding my XC racer, I always had my tyres at 42psi because that is what Ned Overend said in his book he used for racing to avoid pinch flats, and as a big fan I followed the advice (yes, I am that old) totally ignoring any variations in between me and him (all geared up I weight 225lbs). Which wasn't a bad thing as 42psi for my weight is far softer than for his.

    When I experimented with tubeless a couple of years ago I found out for the first time the benefits of lower pressure. It was great the amount of grip I was getting from 28psi in comparison to 42 without feeling increase on rolling resistance. I felt safer and faster.

    At the moment I am using Contis Baron 2.3 with tubes at 30psi front and 35psi rear. I am getting an amazing performance on wet rocky ground and am yet to get a pinch flat.

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