Originally Posted by
ppg677
The thing is, contact patch is way more affected by tire pressure than tire width. A wider rim accounted for an area difference of 0.5%. Going from 120psi to 80psi accounted for a difference in 24%. This implies that tire pressure matters the most. All you dorks running 32mm tires are probably inflating to 80psi!
You are talking about the size of the contact patch, which is controlled exclusively by rider+ bike weight and tire pressure. However, the shape of the contact patch is more important than its size and is the primary variable that affects rolling resistance, as elucidated by the article you linked to. The excessive tire deformation involved in creating the long contact patch of a skinny tire is the reason that skinny tires have higher rolling resistance than fat tires given the same tire pressure. If you choose to keep rolling resistance constant rather than pressure, then the pressure in the fat tires needs to be much lower than the pressure in the skinny tires. Reducing the pressure in this way is what most people do, because it has two additional advantages: 1) comfort; 2) less energy lost due to bouncing the bike and rider up and down on roads that are not billiard-ball smooth.
Leonard Zinn explains this quite well:
http://velonews.competitor.com/2012/...rethren_209268