I think we had this discussion before but it is time to revisit it. I have been riding Vittoria Corse G+ 25 mm tires. Somehow I had gotten the idea that these were faster than the 28 mm tires I had been using 5 or so years ago. Well, Since I have been switching over to clinchers again I got a set of Michelin Power 28 mm clinchers.

There is a sharp descent and a long slightly downhill section I travel on regularly. There is a radar speed limit sign on this route so that I can double check my speedo. My speed through this rough area is normally 24 mph on the sign and about that on my speedo. I just changed over to the 28 mm tires and did that section and the radar reported 26 mph through this section. And the fatter tires at a 10 psi less inflation pressure rode so much smoother that I cannot for the life of me remember why I changed to the 25's.

Before I had 23's on my Time and you simply could not ride that Time with 23's on it unless you had a butt of cast iron. When I changed to the 28's on the Time it was and entirely different bike.

As you probably know, I am 6'4" and 190 lbs so I'm sure there is some dividing point though I don't know where that might be since the Tour riders are using 26 mm sew-up tires on their bikes. But I can tell you I won't make that mistake again and I will be riding 28's from now on.