Page 3 of 10 FirstFirst 1 2 3 4 5 6 7 ... LastLast
Results 101 to 150 of 452
  1. #101
    mtbr member
    Reputation:
    Join Date
    Feb 2007
    Posts
    247
    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
    mtbr member
    Reputation:
    Join Date
    Jul 2006
    Posts
    2,639
    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
    old fart
    Reputation:
    Join Date
    Mar 2010
    Posts
    1,203
    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
    mtbr member
    Reputation:
    Join Date
    Apr 2008
    Posts
    2
    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
    New MTB XC Racer
    Reputation: Rum Runner's Avatar
    Join Date
    Feb 2008
    Posts
    253
    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,
    Paul

  6. #106
    mtbr member
    Reputation: Tillers_Rule's Avatar
    Join Date
    Sep 2004
    Posts
    544
    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
    mtbr member
    Reputation:
    Join Date
    Jul 2006
    Posts
    2,639
    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
    mtbr member
    Reputation:
    Join Date
    Sep 2007
    Posts
    3,331
    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
    mtbr member
    Reputation: Noclutch's Avatar
    Join Date
    Jun 2010
    Posts
    792
    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
    old fart
    Reputation:
    Join Date
    Mar 2010
    Posts
    1,203

    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
    old fart
    Reputation:
    Join Date
    Mar 2010
    Posts
    1,203
    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
    old fart
    Reputation:
    Join Date
    Mar 2010
    Posts
    1,203
    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
    mtbr member
    Reputation:
    Join Date
    Jan 2009
    Posts
    79
    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
    mtbr member
    Reputation:
    Join Date
    Mar 2007
    Posts
    655
    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
    www.quinnphoto.smugmug.com
    07 S-Works Enduro SL - Sold
    08 Epic Marathon - Sold
    2012 Stumpy EVO 29er frame up build

  15. #115
    mtbr member
    Reputation:
    Join Date
    Jul 2006
    Posts
    2,639
    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
    mtbr member
    Reputation:
    Join Date
    Oct 2009
    Posts
    6,543
    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
    mtbr member
    Reputation:
    Join Date
    Mar 2007
    Posts
    655
    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
    www.quinnphoto.smugmug.com
    07 S-Works Enduro SL - Sold
    08 Epic Marathon - Sold
    2012 Stumpy EVO 29er frame up build

  18. #118
    old fart
    Reputation:
    Join Date
    Mar 2010
    Posts
    1,203
    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
    mtbr member
    Reputation:
    Join Date
    Dec 2009
    Posts
    3,489
    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
    mtbr member
    Reputation:
    Join Date
    Oct 2009
    Posts
    6,543
    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
    mtbr member
    Reputation:
    Join Date
    Sep 2006
    Posts
    47
    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
    Nouveau Retrogrouch SuperModerator
    Reputation: shiggy's Avatar
    Join Date
    Dec 1998
    Posts
    48,307
    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?
    mtbtires.com
    The trouble with common sense is it is no longer common

  23. #123
    mtbr member
    Reputation:
    Join Date
    Sep 2006
    Posts
    47
    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
    mtbr member
    Reputation:
    Join Date
    Dec 2009
    Posts
    3,489
    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
    mtbr member
    Reputation:
    Join Date
    Jul 2006
    Posts
    2,639
    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
    mtbr member
    Reputation:
    Join Date
    Sep 2006
    Posts
    47
    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
    mtbr member
    Reputation:
    Join Date
    Sep 2006
    Posts
    47
    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
    mtbr member
    Reputation:
    Join Date
    Jul 2006
    Posts
    2,639
    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.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  29. #129
    mtbr member
    Reputation:
    Join Date
    Sep 2006
    Posts
    47
    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
    mtbr member
    Reputation:
    Join Date
    Dec 2009
    Posts
    3,489
    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 12:24 PM.

  31. #131
    mtbr member
    Reputation:
    Join Date
    Sep 2006
    Posts
    47
    Thank you for the link. I love to read stuff like this.

    Chris.

  32. #132
    mtbr member
    Reputation:
    Join Date
    Feb 2004
    Posts
    555
    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
    mtbr member
    Reputation:
    Join Date
    Sep 2007
    Posts
    3,331
    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
    mtbr member
    Reputation:
    Join Date
    Jan 2011
    Posts
    282
    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
    mtbr member
    Reputation: rmasse10's Avatar
    Join Date
    Aug 2010
    Posts
    171
    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.
    Customize your Gear...Performance Moisture Wicking Apparel
    Custom Performance Apparel

  36. #136
    mtbr member
    Reputation:
    Join Date
    Feb 2007
    Posts
    247

    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
    mtbr member
    Reputation:
    Join Date
    Sep 2007
    Posts
    3,331
    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
    mtbr member
    Reputation:
    Join Date
    Jul 2006
    Posts
    2,639
    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.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  39. #139
    mtbr member
    Reputation:
    Join Date
    Feb 2007
    Posts
    247

    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
    mtbr member
    Reputation: ancient rascal's Avatar
    Join Date
    Mar 2010
    Posts
    3,602
    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.
    Still searching for my red headed hairdresser Tiffany. "Economic Mother Nature" ... Knocks at door! -AR

  41. #141
    PVR
    PVR is offline
    Crash Test Dummy
    Reputation: PVR's Avatar
    Join Date
    Oct 2006
    Posts
    239
    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
    mtbr member
    Reputation:
    Join Date
    Feb 2011
    Posts
    1
    Quote Originally Posted by ancient rascal
    Click image for larger version. 

Name:	img_1406-1 (2).jpg 
Views:	1235 
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
    mtbr member
    Reputation: ancient rascal's Avatar
    Join Date
    Mar 2010
    Posts
    3,602
    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 !
    Still searching for my red headed hairdresser Tiffany. "Economic Mother Nature" ... Knocks at door! -AR

  44. #144
    mtbr member
    Reputation:
    Join Date
    Apr 2011
    Posts
    5,012
    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
    mtbr member
    Reputation: TORQ's Avatar
    Join Date
    Apr 2011
    Posts
    29
    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.

  46. #146
    mtbr member
    Reputation:
    Join Date
    Apr 2011
    Posts
    16
    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
    New MTB XC Racer
    Reputation: Rum Runner's Avatar
    Join Date
    Feb 2008
    Posts
    253
    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,
    Paul

  48. #148
    GT FIEND
    Reputation: SGP495's Avatar
    Join Date
    Jun 2011
    Posts
    160
    :

  49. #149
    New MTB XC Racer
    Reputation: Rum Runner's Avatar
    Join Date
    Feb 2008
    Posts
    253
    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

  50. #150
    mtbr member
    Reputation:
    Join Date
    Jul 2011
    Posts
    2
    We try and take the hassle out of y

Page 3 of 10 FirstFirst 1 2 3 4 5 6 7 ... LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •