Tom A. wrote:
Cajer wrote:
Also to provide another point of info, on Bigham's hour record attempt they lowered the pressure from the traditional ~200 psi to ~130 psi and round rolling resistance reductions even on the very smooth track surface even with centripetal forces providing additional load on the tires. So I am starting to believe that quite low pressures are the way to go on road.
Interesting...and it matches some data shared with me a long time ago about some informal tests done at the Carson, CA velodrome. Do you happen to know what the track surface is at the velodrome Bigham used? The speculation at the time was that if tire pressures are too high (i.e. 200 psi), then the compliance of the track itself starts coming into play.
I did some tests around the local high school running track one time, which has a "compliant surface"...it had a quite dramatic effect on the measured Crr. Additionally, I know that Josh has seen in his Silca testing differences in Crr for freshly laid asphalt vs. the same surface that has "cured" for a few months. In other words, surface compliance matters ;-)
Of course, surface compliance is basically why MTB tests usually result in: "the fastest pressure is the lowest you can run without pinch flatting" :-)
It was a wooden track. He did testing at Grenchen Switzerland. I'm not familiar with the track, so I can't say if it's more or less compliant than other wooden tracks.
I totally agree that a significantly softer surface would create higher rolling resistance. It's basic tribology. With this recent realization. I'm much more willing to accept lower pressures being better. But I'm a bit less convinced on wider tires at same casing tension/equivalent pressure without seeing the rolling road setup. However the easy part is knowing lower is better. The hard part is figuring out how much lower.
I'm also super curious what layup tricks Zipp is playing to try and get the claimed very large hysteresis gains between the 404/454.