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Recreational Cyclocross and Gravelbiking This has to be the most physically intense sport ever invented. It's high speed bicycle racing on a short off road course or riding the off pavement rides on gravel like :The Dirty Kanza". We also have a dedicated Racing forum for the Cyclocross Hard Core Racers.

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Old 11-17-08, 01:49 PM   #1
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Tell me about tire pressure

I'm new to cross racing this year. I've done three races so far and have at least one more to go. The weather and conditions were completly different for each race. Yesterday's race was on gound that had over 1" of rain on Saturday and a coating of wet snow on Sunday. During the race the ground got more and more sloopy and riding some sections of grass was like riding in peanut butter. During warmups I felt my rims bottoming out when going over sunken timbers so I aired the tires at 60 lbs for the race. When watching the A race later on I noticed that many of the riders had a lot less air in their tires, I could see the flex in the tire as they crossed a sidewalk near the finish line. I'm thinking I rode with too much pressure. I did have some slipping when going up steep hills but it was very wet also.

I weigh 190 and my Trek's tires are 32cm width. What is a good rule of thumb regarding tire pressure during racing and under various conditions?
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Old 11-17-08, 03:06 PM   #2
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For performance, the lower the better is the general rule. Better traction and lower rolling resistance over bumpy ground.

For clinchers, the tradeoff is pinchflatting. For tubulars, the tradeoff is folding a tire (hence losing traction and maybe crashing, or worse yet pulling the tire from the rim). You can run tubulars at lower pressures because the risk of pinchflatting is minimal.

There's no rule of thumb. Everybody rides differently. You have to experiment in training, try going as low as 30 and see what happens. No shame in running them a bit conservatively high.
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Old 11-17-08, 09:37 PM   #3
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I weigh 190 and my Trek's tires are 32cm width. What is a good rule of thumb regarding tire pressure during racing and under various conditions?
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Old 11-17-08, 11:13 PM   #4
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haha, nothing to add but that
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Old 11-18-08, 08:23 AM   #5
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OK, the tires are 32mm I'm not that conservative.
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Old 11-18-08, 09:17 AM   #6
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I weigh about 190 and ride 32mm WTB cross wolfs. 60 is a pretty safe PSI, that being said, I have pinch flatted on a fast rocky descent at 60. I usually run about 45-50 in the front and between 55-65 in the rear depending on the course.
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Old 11-18-08, 10:38 AM   #7
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For the Broadview race, I rode 35 psi in my Michelin Mud 2 clinchers. It was great for the most part, but in the down hill turn right before the bridge I had some problems with the rear folding. I'll have to introduce myself next time.
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Old 11-18-08, 10:55 AM   #8
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65 -70 psi out back
60 psi in front

any higher and the traction on the climbs isnt as good.
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Old 11-18-08, 11:56 AM   #9
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For the Broadview race, I rode 35 psi in my Michelin Mud 2 clinchers. It was great for the most part, but in the down hill turn right before the bridge I had some problems with the rear folding. I'll have to introduce myself next time.
I'm the old guy racing for Stark Velo in the C races. Hope to meet you in a couple weeks in Copley.

That was some turn to make. After slogging thru the water being able to ride down the steep hill on recycled asphalt was a break. A team mate warming up for the B race missed the metal screens nailed to the bridge deck and went down while riding before the race. I had trouble at the top of the hill after the bridge with my rear tire slipping, never lost momentum, but on each lap I spun the rear tire.
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Old 11-18-08, 12:21 PM   #10
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65 -70 psi out back
60 psi in front

any higher and the traction on the climbs isnt as good.
Seriously?

I wouldn't even run that high on the road.

35-40 psi on clinchers.
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Old 11-18-08, 12:30 PM   #11
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I'm the old guy racing for Stark Velo in the C races. Hope to meet you in a couple weeks in Copley.

That was some turn to make. After slogging thru the water being able to ride down the steep hill on recycled asphalt was a break. A team mate warming up for the B race missed the metal screens nailed to the bridge deck and went down while riding before the race. I had trouble at the top of the hill after the bridge with my rear tire slipping, never lost momentum, but on each lap I spun the rear tire.
I'll be sure to introduce myself. I was racing B with a black wool jersey on and a Redline Conquest pro.

I think that was a pretty common problem climbing out of the bridge, trying to stand up and hammer, but keeping your weight back far enough that you wouldn't start spinning out.
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Old 11-18-08, 04:29 PM   #12
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I weigh 160 I ride 28 front, 30 rear on 32mm tubulars on most courses.
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Old 11-18-08, 04:50 PM   #13
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Seriously?

I wouldn't even run that high on the road.

35-40 psi on clinchers.
On the road? I run 120 psi in my 700x23c tires

If I go much less than 50-55 psi in my Ritchey Speedmax 32c clinchers it will bottom out very easily on the exposed roots and ruts at my local cross course.
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Old 11-18-08, 08:34 PM   #14
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i found that my bike cornered MUCH better when i reduced pressure from 60 down to 40. i keep the psi at that level now and i like it
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Old 11-19-08, 07:32 PM   #15
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On the road? I run 120 psi in my 700x23c tires

If I go much less than 50-55 psi in my Ritchey Speedmax 32c clinchers it will bottom out very easily on the exposed roots and ruts at my local cross course.
On a road bike I'll run 120-140 psi, riding my cross bike on the road maybe 60 tops, in a cross race 'lll use speedmax or mud 2's, 35-45 psi, depending on how wet/muddy it is.
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Old 11-19-08, 07:58 PM   #16
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I run ~25 PSI with Michelin Mud 2 clinchers. I weigh about 150#
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Old 11-19-08, 08:21 PM   #17
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It all depends on tire, wheel, rider, course conditions.

I run tubulars at 30psi. I run clinchers at 40psi. I've found that running road tubes helps cut down pinch-flats.
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Old 11-20-08, 12:46 AM   #18
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I ran 50 psi in my 35mm Maxxis Locust tires in the Broadview race and never had a problem with insufficient traction (I weigh 145). In retrospect, I could have gone lower because there was nothing to pinch flat on...by the time the A race came around, the whole course was a continuous trough of goo.
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Old 11-24-08, 11:52 AM   #19
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I ran 50 psi in my 35mm Maxxis Locust tires in the Broadview race and never had a problem with insufficient traction (I weigh 145). In retrospect, I could have gone lower because there was nothing to pinch flat on...by the time the A race came around, the whole course was a continuous trough of goo.
Sorry for the delay in a reply, I was on vacation for a few days. My concern with pinch flating in the Broadview race was that everytime I crossed over the buried timbers, in the section before the soccer fields, I was bottoming out the tire and rim. Does less tire pressure allow the bike to ride through the goo/mud faster? If I'm interperating the responses correctly, I should be riding with as little tire pressure as I can get away with in soft conditions?
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Old 11-24-08, 12:34 PM   #20
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Sorry for the delay in a reply, I was on vacation for a few days. My concern with pinch flating in the Broadview race was that everytime I crossed over the buried timbers, in the section before the soccer fields, I was bottoming out the tire and rim. Does less tire pressure allow the bike to ride through the goo/mud faster? If I'm interperating the responses correctly, I should be riding with as little tire pressure as I can get away with in soft conditions?
You have it kind of backwards.

The big irony is that the conditions that are most likely to cause pinch flats (bumpy, rocky, rooty stuff) are the ones that most reward lower PSI. Which is why people run tubulars (or tubeless).

If you go over a rooty section and never bottom out, it means that you are bouncing around more than necessary. But of course if you really bottom out on a clincher, you almost surely are going to pinch-flat.

Muddy stuff, on the other hand, is usually pretty smooth, so more tire pressure actually might help the tire cut through the mud and find the bottom a bit easier. (Debatable.)
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