Originally Posted by
subgrade
Does really a 4-7 mm change in tire width make a real difference in aerodynamic drag unless the rest of the bike+rider is as aero as it gets? (I doubt that can be said about any rider who isn't attempting a world record)
I’m not sure what that would have to do with the tires. The improvement should be the same regardless of the aerodynamics of the rider and rest of the bike.
And when you factor-in the decrease in weight and rolling resistance, a 25 or 28 will likely be noticeably faster, as long as the surface is smooth.Whereas a 32 will shine on rough surfaces.
It really depends on where you ride. If your routes are silky smooth, it would make no sense to run the larger tire, and vice-versa for a rough surface.