Originally Posted by
HTupolev
If we assume that the crr difference between a Gatorskin and a GP5000 in steel drum testing is comparable to the difference on an actual road, for an average bike+rider the Gatorskin is going to cost somewhere on the order of a mph when riding a flat road at 20mph. For a non-fit-related bicycle change, that's pretty huge.
Well, no, steel drum testing is not actually relevant to real road conditions. That is the lesson we've learned over the last few years, and it's why many, many cyclists have reduced their tire pressures. We now know that if the road surface has any sort of roughness, then a hard, high-pressure tire will cause a loss of speed from bouncing over the irregularities on the road.
So now that people are using anywhere from 60-90psi in road tires, as opposed to the 100-130psi that used to be commonplace, tires like the Gatorskins have a real advantage. The "rolling resistance" factor gets swamped by better grip, better durability, and better puncture protection. All of those claims of people having a "harsh ride" on Gatorskins was just from user error: they were running higher than optimum pressure.
Also, a 1 mph change in speed is not that much. It's something that an actually fit rider would never notice, especially when riding solo. The ONLY time a change like that might matter is during some competitive event, but no one is using Gatorskins for competiton (but they will use them for training).