I've been wondering about this lately as I've switched from 26x1.5 to 26x1.9 slicks and then 26x1.95 knobbies. The narrower tires were too painful to ride and had such unpredictable handling that I switched to the 1. 9 slicks for a few weeks. A sidewall failure got me to switch back to the 1.95 knobbies (these were all old tires I had used in the past) with my commute times being about the same and some surprising readings of the speedometer when I thought I was just plodding along. The wider tires use less pressure too, now that we know lower pressures don't mean less speed does anyone know how to figure out what pressures to use? I had been using the maximum listed on the tires for both front and rear before fwiw.