Husband and I both changed to Bontrager Race Lite 25's on our FX 7.5's. It made a noticeable difference in our speed. Went with the Race Lites because I don't want to worry about flats. They felt a little narrower for the first 5 miles or so, but then felt just as stable as the 32s. Went to the 25's instead of 28s because I wanted to notice a difference if I was going to spend the money for the kevlar tires. Really happy about the move. I also came from bikes with wide tires prior to the FX.