Originally Posted by
asgelle
The length of the contact patch is a first order factor in rolling resistance. Rolling resistance is the difference in the force required to compress the front of the contact patch from what is returned at the trailing part in the direction of motion. The longer the contact patch, the greater the component in the direction of travel. It's this geometric factor that gives rise to the decrease in Crr with wider tires ( all things equal etc.). Bicycle Science has a good explanation of this.
I understand where rolling resistance comes from and how it works.
But you were talking about the
change in the contact patch area due to stiffer rubber and the like, and speculating about how much the difference in the contact patch changed rolling resistance. That would be a second order effect on rolling resistance, if it's even been empirically determined to be true. It's not the shape itself, but what happens to the rubber around and near the edges.
To be clear, we aren't talking about tires with different inflation pressures, but other elements causing different deformations.
And I am skeptical of both having more than a trivial change, and that in a tire it would be less resistance thereby, because most tire material qualities that I think of causing a smaller and/or rounder area of contact will cause greater rolling resistance (first order), which would oppose the presumed (theoretical?) improvement due
only to the shape. So I question whether that's been empirically proven, or is just theoretical.