Results 1 to 29 of 29

Thread: Tubeless PSI..

  1. #1
    mnoutain bkie rdier
    Reputation: rydbyk's Avatar
    Join Date
    Oct 2009
    Posts
    2,822

    Tubeless PSI..

    What are you all running on your tubeless set ups these days for xc race day?

  2. #2
    mtbr member
    Reputation: Fakie1999's Avatar
    Join Date
    Feb 2010
    Posts
    911
    I follow stans divide your weight by 7 method. 20 rear 18 front for me.

  3. #3
    mtbr member
    Reputation:
    Join Date
    Mar 2004
    Posts
    167

    psi

    23 up front 26 on the riear.Stans crest wheels,Racicing ralph 2.4 up front 2.25 on the back,Niner air one ss rigide carbon niner fork.great ride and realy fast.

  4. #4
    mnoutain bkie rdier
    Reputation: rydbyk's Avatar
    Join Date
    Oct 2009
    Posts
    2,822
    Quote Originally Posted by Fakie1999
    I follow stans divide your weight by 7 method. 20 rear 18 front for me.

    Thanks. You mean?

    •Rider weight in pounds divided by 7 = x
    •x-1 = Front tire pressure in PSI
    •x+2 = Rear tire pressure in PSI

    That would put me at Front: 20psi Rear: 23psi (2.1 SB8). Pretty close to what I was doing already...
    Last edited by rydbyk; 03-09-2011 at 11:32 AM.

  5. #5
    mtbr member
    Reputation:
    Join Date
    Sep 2010
    Posts
    436
    Do you guys find that you get rim-strikes occasionally when you have such a low psi?

  6. #6
    mtbr member
    Reputation:
    Join Date
    Apr 2007
    Posts
    914
    It really depends on the tire for me. My downhill tires I run 12 psi and my light weight tires I run at 40 psi. For me it depends on how stiff the sidewall is and if I am running tubless or not. I find on my light weight tires (thin sidewall) and if I run them tubeliss I have to run more PSI to keep the sidewalls from rolling in turns, burping and from bottoming out (hitting the rim on the ground). At 40psi tubeless it feels like 35psi with tubes. So for me tubeless is about not getting flats and not about lower tire pressure. Oh all my tires are non-ust.

    Is anyone else finding that they need more PSI when tubeless? Or am I the only one.

  7. #7
    mtbr member
    Reputation:
    Join Date
    Jan 2008
    Posts
    453
    I hadn't seen the Stan's method of calculating pressure. At 160 lbs, I'd be 22 front, 25 rear. I've been running 28 and perfectly happy, even thought it was soft at first. I might have to try lower. At 28 I'll burp them once or twice a year. Would the lower pressure increase burping chances?

  8. #8
    mtbr member
    Reputation:
    Join Date
    Nov 2010
    Posts
    287
    There's no way everyone could use a calculation based only on weight to determine tire pressure. What about tire volume, inner rim width, and tread width? What about calculating a floating point rider weight distribution?

    Yes, I'd imagine a set of equations could be devised that everyone could use, but you'd need help from a physicist. What's more, the equations would only be as useful as the desired outcome (rolling resistance vs. grip, contact patch vs. sidewall exposure, etc.). At best you might be able to get a set of variables to plan with, but of course you'd still be the ultimate judge of what works best for conditions/goals.

    In other words, you'd still be at the mercy of trial and error.

  9. #9
    mnoutain bkie rdier
    Reputation: rydbyk's Avatar
    Join Date
    Oct 2009
    Posts
    2,822
    Quote Originally Posted by lassiar
    There's no way everyone could use a calculation based only on weight to determine tire pressure. What about tire volume, inner rim width, and tread width? What about calculating a floating point rider weight distribution?

    Yes, I'd imagine a set of equations could be devised that everyone could use, but you'd need help from a physicist. What's more, the equations would only be as useful as the desired outcome (rolling resistance vs. grip, contact patch vs. sidewall exposure, etc.). At best you might be able to get a set of variables to plan with, but of course you'd still be the ultimate judge of what works best for conditions/goals.

    In other words, you'd still be at the mercy of trial and error.

    So....what PSI are you running? It's not that complex unless you are looking to go as lowwwwwwwwwwwwwwww as possible w/o causing a major problem.

  10. #10
    mtbr member
    Reputation:
    Join Date
    Jun 2007
    Posts
    285
    Quote Originally Posted by newnan3
    Do you guys find that you get rim-strikes occasionally when you have such a low psi?

    I trashed my first "tubeless" rear rim from running such low psi.. I've since rebuilt with a flow rim since I've got a bit of caveman in me, but I also don't like the ride when the rear is that low, it gets squirlly so I only ride that low when doing snow rides.

  11. #11
    mtbr member
    Reputation: biglines's Avatar
    Join Date
    Apr 2009
    Posts
    174
    175 lbs, Mavic SLR wheels, Race king 2.2, 25-26 psi front, 29-30 psi rear. I cannot go any lower in the rear because when i venture into the 26-28 psi range the tire wants to roll over on itself in high G curves. I love this setup and will be running it this race season. Lots of grip and give in the tires at these pressures.

  12. #12
    mtbr member
    Reputation: Fakie1999's Avatar
    Join Date
    Feb 2010
    Posts
    911
    Quote Originally Posted by rydbyk
    Thanks. You mean?

    •Rider weight in pounds divided by 7 = x
    •x-1 = Front tire pressure in PSI
    •x+2 = Rear tire pressure in PSI

    That would put me at Front: 20psi Rear: 23psi (2.1 SB8). Pretty close to what I was doing already...
    yeah. I dont know where I read that either. I suppose I should mention I was running stans olympics with stans ravens 26x2.2 at the time. I switched to racing ralphs in 26x2.25 and ran the same pressure. I feel like they run harder, so, I think I could go even lower on those.

    Stans website had a chart on one of the wheel pages, with rider weight and tire size. I cant find it on the new website.

  13. #13
    mutaullyassuredsuffering
    Reputation: used2Bhard's Avatar
    Join Date
    Dec 2005
    Posts
    2,053

    higher

    I run a bit higher than many here. I'm 170lbs and go with 26 front and 30 rear on my 2.4RR/2.25 RR rigid setup, and 32 front 30 rear on my 2.25RR/2.25RR 100mm setup.

    I used to run lower (24psi) until a burp off of a 1.5 foot step followed by a cut tire gave me the opportunity of walking my bike 15 miles in the dark back to my car. I err on the side of caution now.
    Free will is an illusion, people will always choose the perceived path of greatest pleasure.

  14. #14
    mtbr member
    Reputation:
    Join Date
    May 2010
    Posts
    10
    did a very cold and wet 8 hour solo running my racing ralph 2.25's on my tallboy at about 13 front and 18 rear, I wish I could get away with going that low all the time, this was at trails with a lot of sand below the surface, so great quick drainage, not much mud, lots of wet roots, never been faster over that course, just gotta be very aware where you are placing your rear wheel, a few days later dented the crap out of my rear rim and shredded a tire flying through a section I hadnt ridden in a while and coming up short on hopping a creek crossing at speed and stuck my rear wheel into a square edged rock on the other side instead of landing nicely

  15. #15
    mnoutain bkie rdier
    Reputation: rydbyk's Avatar
    Join Date
    Oct 2009
    Posts
    2,822
    Quote Originally Posted by LiamC
    did a very cold and wet 8 hour solo running my racing ralph 2.25's on my tallboy at about 13 front and 18 rear, I wish I could get away with going that low all the time, this was at trails with a lot of sand below the surface, so great quick drainage, not much mud, lots of wet roots, never been faster over that course, just gotta be very aware where you are placing your rear wheel, a few days later dented the crap out of my rear rim and shredded a tire flying through a section I hadnt ridden in a while and coming up short on hopping a creek crossing at speed and stuck my rear wheel into a square edged rock on the other side instead of landing nicely

    Thanks, but how did you manage to do 4,294,967,295 posts?

  16. #16
    mtbr member
    Reputation: sprocketjockey9's Avatar
    Join Date
    Jul 2006
    Posts
    1,215
    Typically run around 20-22 psi front and rear. However, if it's fairly rocky I may go 22/25 as I've been known to ding my rims a bit depending on the tire...

  17. #17
    mtbr member
    Reputation:
    Join Date
    May 2010
    Posts
    10
    7 posts a second....for the past 25 years straight. just picked up a set of this years Schwalbe tubeless ready tires, racing ralph on the back and rocket ron on the front, probably be able to get away with a whole lot less sealant, wonder how low they will go comfortably.

  18. #18
    mtbr member
    Reputation:
    Join Date
    Sep 2008
    Posts
    1,961
    i tip the scales in the low 150's and run in the low 20's. varies some depending on day/course.
    Try to be good.

  19. #19
    mtbr member
    Reputation:
    Join Date
    Dec 2007
    Posts
    34

    Pump Calibrations

    What pumps are being used to set such low numbers?
    I have a Park and a Joe Blow .The Park has 2 lb. incrments but starts off at more than zero, it's somewhere like 5 0r 6 lbs.{has seen better days}
    The Joe Blow has 4 lb increments , more for roadies ?
    I guess i need to find one with 1 lb increments.
    Thanks.

  20. #20
    mnoutain bkie rdier
    Reputation: rydbyk's Avatar
    Join Date
    Oct 2009
    Posts
    2,822
    Quote Originally Posted by RIDESLOW
    What pumps are being used to set such low numbers?
    I have a Park and a Joe Blow .The Park has 2 lb. incrments but starts off at more than zero, it's somewhere like 5 0r 6 lbs.{has seen better days}
    The Joe Blow has 4 lb increments , more for roadies ?
    I guess i need to find one with 1 lb increments.
    Thanks.
    I use a Lezyne now. I think that more importantly, the pump needs an accurate PSI guage. My Lezyne has 5lb increments as far as I can recall. I still find it fairly easy to visualize where I am at on the guage though in 1lb increments.

    I use an air compressor with presta guage sometimes too..(a must for me when setting up my tubeless tires). They both agree on PSI.

    Not sure if it is EXACTLY 21lbs, for example, but it is pretty darn close..

  21. #21
    mtbr member
    Reputation: Fakie1999's Avatar
    Join Date
    Feb 2010
    Posts
    911
    I have a specialized pump that does 5lb increments. Same deal, I just visualize it (usually with needle widths). Its probably not EXACT, but, I just use it to consistently set them at the same pressure. 20 rear is indicated, the front may vary a bit, but, no big deal. Theres also a dial on the outside I can turn that has a arrow on it. So, I can always bring the needle up to where I had the front set to the previous times.

  22. #22
    mtbr member
    Reputation: Okie Dokie's Avatar
    Join Date
    May 2008
    Posts
    1,153
    I run about 23-24 front and 24-25 rear on 29er Crossmark tires. I have been experimenting lately with lower pressures and find that while they grip great I feel the rear tire feeling a bit wobbly over rocky terrain when the rear gets into the 22-23 range. I weight 175lbs.

    I use a digital tire pressure gauge as i feel pretty much any pump is off by quite a bit.

    whybotherme--dang you look a lot bigger then 150+ pounds.
    Originally Posted by XC62701
    Agreed...make it longer. I want to know death is an option

  23. #23
    mtbr member
    Reputation:
    Join Date
    Jun 2010
    Posts
    206
    I'm 180lb, stans rims, I ride nobby nics 29psi and rocket rons 28psi. on new england 1track. I also seem to lose a lot more air across the ride on hot weather days. And i go way lower pressure in the loose stuff or sandy trails. No tubes, never again, sworn off for good.

  24. #24
    mtbr member
    Reputation:
    Join Date
    Jul 2006
    Posts
    35
    Quote Originally Posted by brent878
    It really depends on the tire for me. My downhill tires I run 12 psi and my light weight tires I run at 40 psi. For me it depends on how stiff the sidewall is and if I am running tubless or not. I find on my light weight tires (thin sidewall) and if I run them tubeliss I have to run more PSI to keep the sidewalls from rolling in turns, burping and from bottoming out (hitting the rim on the ground). At 40psi tubeless it feels like 35psi with tubes. So for me tubeless is about not getting flats and not about lower tire pressure. Oh all my tires are non-ust.

    Is anyone else finding that they need more PSI when tubeless? Or am I the only one.
    i dont run pressures that high but like you, tubleless is for not getting flats more so than for low pressure, especially during races. on trail rides i like mid 20's but on race day its high 20's or i will roll and burp and bottom out.

  25. #25
    mtbr member
    Reputation:
    Join Date
    May 2006
    Posts
    12,083
    Quote Originally Posted by Fakie1999
    I follow stans divide your weight by 7 method. 20 rear 18 front for me.

    Formula does not consider tire size ... and should...

    much different pressure for a 1.9 vs a 2.4

  26. #26
    mtbr member
    Reputation: Fakie1999's Avatar
    Join Date
    Feb 2010
    Posts
    911
    Quote Originally Posted by jeffscott
    Formula does not consider tire size ... and should...

    much different pressure for a 1.9 vs a 2.4
    True. I think the chart on notubes.com was better. It had tire size and rider weight.

  27. #27
    mtbr member
    Reputation:
    Join Date
    Oct 2010
    Posts
    284
    Crossmark 2.10 29" non tubeless tires with Stans sealant, on Flow rims, weight 140 lbs ready to ride. This winter riding through woods and mountain roads in snow I used 20psi front 20psi rear. There were a few times I had both around 15psi to try. It was OK but I just felt 20psi was good standard overall psi for the all the condtions I would get into on the trails/roads. These worked pretty well unless things were real deep or started to melt and got mushy.

    I I used 25psi as condtions would get a little better and atleast 30psi after things dry up and get more firm where rocks could become a problem giving rim strikes. If you are getting rim strikes you need to put air in.

    I would say optimal is where you are just low enough to the point where you don't get rim strikes while riding ones riding style. I like the traction factor of the low pressures and the no tubes. Of course the pressure one will also run will hae to be determined by one weight as well.

  28. #28
    mtbr member
    Reputation:
    Join Date
    Sep 2008
    Posts
    1,961
    Quote Originally Posted by Okie Dokie
    whybotherme--dang you look a lot bigger then 150+ pounds.
    not much extra on me right now. i am 5'10" and can easily go over 160lbs if i slip some on my nutrition. last year coming off injury i was in the mid 170's.

    Try to be good.

  29. #29
    mtbr member
    Reputation:
    Join Date
    Apr 2005
    Posts
    704
    kenda Karmas.... 165lb,, 20psi front/ 23-25 rear.... ZTR podium MMX

Members who have read this thread: 1

Posting Permissions

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