Oh right, I got confused, it might actually have been even bigger 28+mm on the TT bikes that was doing well in the wind tunnel testing. 25mm was the older "ski

Oh right, I got confused, it might actually have been even bigger 28+mm on the TT bikes that was doing well in the wind tunnel testing. 25mm was the older "skinnier" size that was prevalent in the peloton, or even 23s or smaller. I think it also became apparent that rolling resistance was reduced on wider tires, so if an aerodynamic (and weight) formula could be made to make 28mm viable, it was better.