I have heard and heard that the wider the tire the slower the tire. I get the concept, but... What is the REAL difference in speed? I am currently 290lb riding 700c x 28 and am going to start commuting both ways to work. I like the idea of going to 32's and am wondering the real difference in speed. I seem to average around 15 mph, would moving to 32's reduce me to 14 mph or is it more like 14.9mph?
Has anyone ever done a real world comparison between two different tire sizes that are one size off, like 23 vs 25, 25 vs 28, 28 vs 32, etc? If so, what did you discover?