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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 09-28-10, 08:39 PM   #1
sabazel
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Duh Question: PSI

I have a question that probably fits in the "duh" category, but I couldn't find the answer in a search.

At what PSI should I run my CX tires? For various conditions? I'm a roadie, but after my first race tonight, I have a sneaking suspicion that the PSI was way too high. If not, well, time to look for another excuse.

I have 700x35 tires.

Thanks in advance for answering my "duh" question.
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Old 09-28-10, 08:57 PM   #2
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There is not one blanket statement, since there a several variables that need to be considered. Are you running tubulars? How much do you way weigh? What are the conditions like?. Generally speaking, I run 30 psi on my front and 35 psi on my back with tubulars, and I weigh 170. I have run lower, but if it is bumpy in spots I tend to bottom out pretty bad. I have never pinch flatted with running as low as 25 psi on the front, but running it that low I think I have just been lucky. When I ran clinchers I usually kept it up around 40 psi.
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Old 09-29-10, 06:32 AM   #3
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Good article:

http://www.cyclocrossworld.com/Tech....ShowDisabled=0
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Old 09-29-10, 08:15 AM   #4
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I run around 28 lbs in my tubulars when I race and maybe 35 in clinchers. In my clinchers I run Stan's sealant in my tubes to avoid pinch flats.
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Old 09-29-10, 12:50 PM   #5
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Clinchers, 700x34, 170lb body-weight. 37psi front, 41psi rear, or thereabouts. Any lower up front and the tire rolls over too much. The rear is a bit firm, but I'll take that over a pinch flat any day.
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Old 09-29-10, 12:56 PM   #6
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It's really something you have to experiment with personally. There is a certain knack to riding low PSI, both in terms of turning and in terms of avoiding pinchflats.

The pressure gauges on floor pumps are inaccurate at low PSI, so get a good one like the Accugage.
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Old 09-29-10, 04:04 PM   #7
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I have had it recommended to me that the top end should be 1/4 of the weight of you plus your bike. For me, that's 45 lbs.

Last year I progressively when lower - to about 30psi on clinchers, at which point I was pinch flatting. This year I'm doing 35 front/40 back. Even at that, I did manage to pinch flat the rear going over a root as I was grinding around an off camber turn. Did the same turn 5 more times the next day at the same pressure and was fine.

Tubulars can get lower.
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