Yup, the 255/50 is equal to the stock 205/75/15 wheel - 27". The 3.42 gear in the Jimmy should easily turn a 255/55/17 tire. The larger size will put my cruise RPM right near my target of 2000-2100 RPMs. The larger wheel also limits the amount I can lower it too. I want to tuck the wheels nice into the wells. I need to make my decision in two weeks. Da Jimmy needs some wheels badly.