So I got a great deal on a pair of 28mm Conti GP5000s with cream side walls. I put them on the Mavic Open 4CDs and they fit on my Basso frame no problem. The tires mic out at 25.5 on those rims. The 25 Gator was about 1.5 mm less than advertised and the 28 GP5000 is 2.5 mm less. Plenty of room all around, but I did have to deflate to fit between the brake pads even with them flipped open. Any idea why the tires are so much narrower than 28 mm when mounted? Rim width?