Originally Posted by
WhyFi
As the casing gets thinner, it's more likely to be more supple and roll better, rather than worse.
Tests by Al Morrison and Tom Anhalt show that brand new out-of-the-box tires have slightly higher Crr than a tire that's been run for 40 or 50 km, but that over time Crr slightly increases. The casing doesn't usually get thinner: the tread compound does. The bottom line is that when racing, we often "break-in" new tires for 40 or 50 km. Some of the lowest Crr racing tires are pretty fragile with very thin treads, so if you use them too much you'll flat during a race and the rolling resistance goes way way up.