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How much psi for xc racing?

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#5 ·
i don't agree with getting numbers from an equation, or off a chart. there's too many variables concerning the terrain, tire size, personal preference, riding style, conditions, etc. just stick to your normal tire pressure unless the course requires a slight adjustment up or down.

when i put my info into one of those things my recommended pressures are WAY off.

whatever you do, don't jack your tire pressure to 35 thinking that you'll go faster. you won't.
 
#6 ·
It's really hard to put a number on someone else's tire pressure, but I can say that I run a few psi lower when it's muddy and slick. I can generate high cornering forces when it's dry and I don't want my tires squishing around on the rims. Lower pressure when it's muddy will provide more contact (and you can't generate high cornering forces anyway). Of course, if you're denting your rims, you need more air.

-F
 
#8 ·
Depending on the course you might need to bump your race psi up a little from what you normally ride because you tend to hit things harder and disregard prudent line choices when your running near max effort.
 
#9 ·
BENKD29 said:
whatever you do, don't jack your tire pressure to 35 thinking that you'll go faster. you won't.
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that depends on the ratio of bumps to plain smooth dirt. if it has no rocks and roots pump them puppies way way up
 
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#10 ·
I'm in the 130lb range and run 18F/20R on my 29er hardtail most days. Still running tubes too, so far so good. If it's a particularly hot, dry day I pump the pressure up a bit. If I know I'm going to the lakes and gonna be in a lot of sand and mud I take some air out when I get there.

I used to run 30psi F/R religiously but I always struggled in the loose stuff and in corners.
 
#11 ·
127.0.0.1 said:
that depends on the ratio of bumps to plain smooth dirt. if it has no rocks and roots pump them puppies way way up
Click to expand...
it's still not faster over the length of a course. if your pressures are jacked you will not be able to corner or brake like your used to. and if there is any loose stuff your going to be sliding all over the place. it will cost you more time than it saves you. especially if you go down when the front washes out.

run your normal pressures +/- a lb or two depending of specific conditions.
 
#12 ·
BENKD29 said:
i don't agree with getting numbers from an equation, or off a chart. there's too many variables concerning the terrain, tire size, personal preference, riding style, conditions, etc. just stick to your normal tire pressure unless the course requires a slight adjustment up or down.

when i put my info into one of those things my recommended pressures are WAY off.

whatever you do, don't jack your tire pressure to 35 thinking that you'll go faster. you won't.
Click to expand...
True, but the NoTubes formula is actually a rather darn good starting point. My wife rides a Niner Air 9 and is the same weight as the OP. Since I air up her tires on her bikes, I know what pressure she runs and prefers in terrain all the way from Moab, to Colorado, to the Black Hills to here in the more buff Midwest for her XC riding and racing. Give or take a pound of psi, the 15-16 front/ 18-19 rear is pretty golden covering the gamut as a starting point for the Ralphs, that body weight, and on the big wheels.
 
#14 ·
+1 to everyday pressures. First races have enough that's new and different without messing with your bike too.

If you're still curious, try some different pressures in training before your second race. :)
 
#16 ·
I would think 20 is a good starting point and you could probably ride less at your weight. Air pressure is so personal and the only way you know is to try it. I ride and race the same pressures on all of my bikes...no need to change it. The No Tubes pressure calc is pretty close to what I use - 24/22ish @160lbs.
 
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#17 ·
BruceBrown said:
True, but the NoTubes formula is actually a rather darn good starting point. My wife rides a Niner Air 9 and is the same weight as the OP. Since I air up her tires on her bikes, I know what pressure she runs and prefers in terrain all the way from Moab, to Colorado, to the Black Hills to here in the more buff Midwest for her XC riding and racing. Give or take a pound of psi, the 15-16 front/ 18-19 rear is pretty golden covering the gamut as a starting point for the Ralphs, that body weight, and on the big wheels.
Click to expand...
I agree, the stan's formula puts me right about where I set it, obviously ymmv but it does get you close.
 
#18 ·
The width of your rim and your tire size will play a big part in this too. I'm 180 and run my pressures in the low 20's. But I'm on 30mm internal rims with 2.35 tires. I wouldn't go that low on traditional narrow XC wheels or I would be destroying rims.
 
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