We tested the same baseline tire three times during our test session – first, in the middle and last – to see whether conditions had changed. We were lucky: the morning was completely calm. It also was overcast, so temperatures did not change. (We later found that temperature greatly affects the rolling resistance of tires.) One morning was not enough to complete our testing, so we spent many more days on the test track. Sometimes we went out at 4:30 a.m. only to have a light wind spring up. All we could do was go home and hope for better luck next time.
At the end, we had pages and pages of measurements that we formatted for analysis. During our analysis, we found some interesting results:
The speed differences between our tires were even greater than those tested by TOUR. The fastest tire, the Deda Tre, rolled 20% faster than the slowest, the Rivendell Nifty-Swifty. A 20% difference in on-the-road speed is huge!
Wider tires roll faster. A Michelin Pro2 Race in 25 mm width was faster than the same tire’s 23 mm version, which in turn was faster than the 20 mm version.
Very high tire pressures don’t roll much faster. Above an “adequate” tire pressure, the tire’s speed increases only very slightly with higher pressures. This contradicted the tests performed on steel drums, including those by TOUR.