When changing flats, I have usually used a tire iron to get the tire back on, but can usually do without it if I need to. I just got a new rear wheel built, and the fit with my tire is so tight that it is impossible to get the last part of the tire on without the iron. About half the time, however, this results in a new flat as the tube gets pinched by the iron.

Is it possible that this rim is slightly larget than my old one (though it was really hard to do it before, but now it is impossible).

This is a Canondale F700 moutain bike with 26" wheels, and I am using slicks (commuting).

Thanks!