Originally Posted by
neil
Racers use extremely small tires because of their cornering profile (smaller tire = less deflection = fewer wipeouts). It has nothing to do with speed. Wider tires tend to be a bit slower because they have lower pressure limits, but that's a pretty small impact.
And footprint - wider tires have a wider contact patch so increased rolling resistance... but yeah, for commuting tire width effects speed a lot less than most would expect.