I rely on course condtions to dictate tire pressure. If it's wet, use 100#. If it is dry, but with very few turns, I use 160#. If it is dry, but a technical course, I use 130 lbs. Some say it's a waste using high pressures, but my real-life experience says different. If you want conmfort, use a lower pressure. If you want speed, pump 'em up hard.

For our weight - anything above 130 is pointless. You don't get any improvement over that - but like YGBK posted - if it's wet, lettem leak a little. You want more contact patch. Dry - make 'em hard. Remember - when you starte pumping them to 140-150-160psi, you're adding weight to your wheels. That's a LOT of air molecules you're squeezing in there. really.

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Animal!!!

By the way, does the pressure decrease over time like a tubed tire? Or does it maintain it's pressure longer?

Most tubulars have tubes so they lose pressure just like clinchers. I have a pair with latex tubes that require pumping up every day. I also have a pair of tubeless Tufos that maintain pressure for weeks.

I am with muppet on this one, anything over 130 psi is a bad idea, even if the tire is labelled "170 psi".

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Tom Demerly
The Tri Shop.com

I'm with Tom D. 130 is lots.

Does anyone have any real science behind pressure, not just what they think feels right? I like 160...it feels fast...but is it? Anybody...?

On a dry, flat course I pump my sewups to 160#. I haven't had a flat (now I'm sure I will) and when you hit a piece of small glass with pressure like that it just crushes it into sand. So I puncture less. Plus, when the tire pressure gets below 120-130#, I can feel the difference as increased perceived effort. The higher you go in pressure, the less contact patch on the pavement. When mine are pumped high for a race, I can hold higher speed with less effort. That's my gauge. Everybody's different though. Experiment. Find what you like. Suffice to say, my race setup is not comfortable (P2K with ZIPP disc/HED3 tri-spoke), but it is fast.

I tried to go with Tom D. recomendations of only 130psi, but that is soft when compared to 160. The handling becomes loose and delayed and the comfort issue on a sub 100km ride is not very noticable, if at all. I noticed most triathletes have difficulty cornering anyways, so it is not a big deal I guess. If you are doing an IM I would imagine comfort is more than an issue. In Oly and long course distances you are on the bike for less than 2.5 hours, no time for discomfort to really be noticed. Unless you are on some majorly rough road that is not paved at all (yes, I regret running more than 100psi during that race) or your positioning is way off.

I think you should go out and ride a few different pressures and do what feels best. Be carefully pumping them up high though, I bent the rod on my pump at my last RR.

I ride a steel cyclocross bike with a deep front and a renn disc (yes, weird setup, but faster than most). We will see how the P2k feels next year, but the cross bike stays for RR and crits.

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Reverend Dr. Jay
Lake of the Pines Triathlon fastest bike course record holder - Golden State Super Sprint fastest tri course record holder - Wildflower Long Course slowest run course record holder (4:46:32)

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"If you have a body, you are an athlete." -Bill Bowerman

About 80% of rider weight is usually a good number.

What do the Posties ride for time trials? Seems like they would have probably figured out what's best.