Here's a thought: Yesterday's ride was on Conti GP3000s, 120psi. Today, same bike, same wheels, Michelin Pro Race, 120psi. On my life I swear that the Michi's were far and away more comfortable and smooth. I've raced and trained on Conti's for a decade and a half. I'm now a no holds barred Michi convert.

I tend to run 120psi on my racing tires 19mm Continental Competition GP tubulars. Though I admit this is not the most comfortable of rides, 19mm tires are a bit more aero "whatever that means" and 120psi insures the tires stays in its proper place. I race oly distance so barely have time to notice the rougher ride. It has been proven that anything above 120psi is not advantageous and may actually increase the chances of a tire blowing. None of the pros I know ride above 120psi.

On my training bike, I run 110psi on 22mm Michelin Pro Race clinchers. Great wheels and just the right psi for a 140lbs rider.

I think anything less than 90psi will increase the chance of a flat or damage to the wheel and slow you down noticeably. Even in the current sub 20 temperatures here in NY, I still don't go below 100psi ever.

Rolling resistance is a very small part of the total forces that limit speed on a bike, as long as you are reasonable in your tire pressures. I don't think you'd actually see any statistically significant difference in a 40K tt if you rode with tires at 120 or 100psi (as long as the tire was designed to run at both of these pressures). In fact, if you were more comfortable, you might stay more aero, and be faster at 90 psi! And at 135 lbs., I would think it wouldn't be quite as important as if you were 235!

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Zipp suggests that you dont go over 125 PSI on there clincher rims.They claim incresed rolling resistance over that pressure.

Quote: "So my question is, how much more watts does it take to push a tire that is inflated about 20 psi less? "



The easy answer: No one knows. And if you read my rant about Aero testing, this falls in line. I suppose time trialing is relatively new and triathlon definetly is. But I'd be surprised if anyone in the world could tell you that on X road surface riding the same tire at 100psi vs 120psi will cost you X amount of watts per mile. So, we as triathletes need to hash it out for ourselves. You'll hear Scott, Molina, Allen, Tinley talk about how they were inventing tri training (as there was no precedent on how to train for the IM) and still today, we are inventing things too, like perfect TT air pressureas well as others. When you figure it out let me know.

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