Originally Posted by
tarwheel
However, wider tires are generally heavier than narrow ones, and that's why most cyclists perceive them to be slower.
Weight isn't the cause.
The fastest tires are made for performance enthusiasts who don't mind 2000 mile lifetimes and have historically run 23mm tires. Their manufacturers have a history of not offering the same construction in wider sizes, even a 25mm tire which won't fit some racing frames. This is slowly changing - breaking with tradition in 2014 Continental will offer its raciest clincher (the GP4000S II) in a 28mm width.
Wider tires are usually built for a different markets that value lifetime and flat resistance over rolling resistance with the resulting stiffer carcasses having higher rolling resistance.