Quote Originally Posted by Seajay View Post
Oakleaf...Thanks for the stimulating conversation on a boring day. I should be working.

Consider that a tire is designed to take up load/bumps (energy) at the front of the contact patch...and release that energy at the end of the contact patch.

If your tire pressure is above that on the engineered chart.... the energy will not be taken up by the tire...it will pass THROUGH the tire, into the fork, frame and YOU where you absorb it (convert it, actually) with your body (same as a tire with a very stiff sidewall (like an Armadillo) ....THUS never being returned to the road through the back of the contact patch = HIGHER rolling resistance not lower.

The other consequence here is that the weight of the bike and your body are forced to travel up/down/up/down with every imperfection in the road as opposed to that mass traveling on an even plane.
My turn for conjecture... it must take MUCH more energy to have you and the bike move up and down than it does to move it smoothly down the road.
This is mostly true. If you run a higher pressure, the ride isn't going to feel as smooth, and some of the shock is going to be transferred to the fork/frame/rider instead of being diffused by the tire. On the road, this is pretty minimal, because you're talking about high pressure tires anyway. This isn't like in cyclocross where on the race course you'd run maybe 40psi in your fatter tubular tire (tubies to help avoid pinch flats you might get with clinchers running over a tree root), but on the road, you'd want to max that tire out at 60psi for a faster ride. The difference felt there is probably much greater than going from 100-120psi on a skinnier road tire. You also need to take into account that there is less rolling resistance (though this depends on the specific tire design) with higher pressure which may translate into a faster ride (make more of a difference in the forward direction) than diffusing some of the vertical shock.

I don't even reduce air pressure when it's wet. I know how my tires grip at their usual pressure, and so I stick with that. Perhaps if I had the cornering benefits of tubulars, I might change that, but then dry condition pressure for road tubulars is higher than what i run with clinchers anyway.