Originally Posted by
cxwrench
Others that are much more intelligent than I have tested. Higher pressures (over 100psi in 23-25mm tires) has been proven time and again to be slightly slower than lower pressure. The harder the tire the lower the mechanical grip, so less traction. Ride quality? The answer is obvious. To be honest the differences in rolling resistance are very minor compared to the gains in comfort and traction. If you're feeling every little bit of pavement texture and every small bump in the road it might feel fast but in reality if you're feeling these things it's because the bike is bouncing off of them...and if that's happening you're experiencing higher levels of rolling resistance. The tire is the only suspension on a road bike...let it do it's work. You'd have to drop down to very low pressure before you'd start losing energy to tire flex (hysteresis). For most people this would be lower than the pressure at which the tire started to feel too 'mushy' or flexible.
If you're running 23mm tires it's a tradeoff between ride quality and possibility of a pinch flat. For me, pinches are more likely to happen when riding in a group when visibility, and ability to avoid obstacles is diminished. It just takes one small rock to cause a pinch and I've had a reasonable number of them over the years. I'd rather have a slightly harsher ride and minimize the possibility of a pinch although I'm also lazy and don't pump my tires before every ride so I would usually pump 23s initially to 110 and then use the finger test to determine when to add more air.
Whether pressures above 100psi result in slower speed is entirely dependent on the surface. Our local crits are run in industrial parks on decent pavement and I think it would be tough to say for certainty what the optimum pressure is without testing.
For most of the last year this is moot to me as I haven't been doing any group rides and I've been riding on cushy 28mm tubeless tires. I start at 70 and can go over a month before reinflating.