[ActorNightly]

25 and 28 are basically same width. Also wind tunnel testing is not really representative of real world condition given real world turbulence, but I dunno if that would really affect results.

Im just against the general saying that wider tires are faster. This implies that fat bike smooth tires are the fastest, but we know that this is ridiculous. 25 to 35c probably doesn't matter too much aero wise at regular cycling speeds, but going all the way into 40-50c does.

[arghwhat]

The issue is that narrow tires have a very, very inefficient suspension behavior, and road surface and rider movement causes it to be constantly exercised. That does not mean that you gain anything from going nuts - there are diminishing returns just like there is for slimming the tire for aerodynamics.

What tire is best depends on the surface, the rider and the speed. On a perfectly paved road at high speed and with a light, stable rider, 25 might be right. On regular roads, 35 might be faster. On a bumpy mess, "smooth fat bike" tires would indeed be faster still - assuming you can stay upright without the tread. There's a reason you don't take a road bike with 25mm tires to do downhill mountain racing.