Originally Posted by
Redbullet
2. "Wider tire is always faster": That depends. Deeper research shows that gains that may come from using 25 (or 28)mm tires instead of 23mm can easily be offset and even overcame by loses due to air drag, if wider tires are mounted on shallow rims (i.e.: if tire profile is larger than rim profile and the system does not show a continuous shape). So, I doubt that, overall, 25 mm tires would be faster on my shallow rims, than 23 mm (and, by the way, in real life, 25mm tires measure some 26-27 and 23mm tire measure 24-25).
I haven't parsed all of the replies, but I'd be surprised to see anyone speaking in absolutes like, "wider is always faster."
I think that most people that have embraced wider tires realize that there are potential trade-offs, they're faster under certain conditions and that those conditions aren't terribly usual for many of us. For my less than pristine roads and often quite lengthy rides, I have no doubt that I'm better served by my 28s at ~60psi than I would be by 23s at 90+
And, by the way, in real life, tire measurements vary. Many manufacturers have recently gone to more realistic nominal sizes to reflect their WAM (width as measured) on modern rims with internal widths in the 19-21mm range. Buy a Conti GP5k, Schwalbe Pro 1 Evo, Pirelli P Zero Velo or a number of other recent releases and they'll measure under their nominal size on your narrow rims.