Originally Posted by
waterrockets
Well, that's the key there. 25s are rated at a lower psi than 23s. When you inflate to a given tire's max/recommended psi, the 23s are usually a touch lower crr. That makes a difference because a 25 will blow off the rim before a 23 at higher pressures because of the increased surface area straining against the same bead contact area/hook strength.
I think this is an instance of looking at the trees not the forest.
So, there are two ways you can increase rolling resistance:
The first, is to run a pressure so low which allows for additional hysteresis in between the tube, tire and road.
The second, and more consequential form of rolling resistance, is the speed lost to surface irregularities with a tire pressure which can not deform to road surface changes. By running too high of a tire pressure, you are in effect "bouncing" over the road and not letting the tires do their job of shock absorption.
Typically for a perfect balance between the two forms of rolling resistance you should be nowhere near a tire's max PSI. For many riders, you should be in the 100-110psi range. Such that your tire can deform to road irregularities but that you don't have a significant loss of hysteresis between the tube/tire/road interface.
Most rolling resistance data shows that a wider tire rolls faster even in a laboratory sense. And additionally, most on road tire testing shows that above 120psi a person sees significant loss on any road that is less than ideal.
It is counter intuitive that 25mm tires pumped to a moderate pressure roll faster than 20mm tires pumped to their gills, but it's not opinion. It's data.