On my hardtail I had been running 2.35 60d high rollers for a few months. I wanted to try some 2.5s for the race in Parkfield, CA. At cambria I got 2.5 40d mobsters. I mounted them and they are the same size as my 2.35s. The back might be barely a hair wider. Its not like I have thin rims. I have Mavics; ex325 in the rear, and an ex 721 in the front. Shouldn't I be able to notice a difference? My friend was completely stumped.