How big are you talking? You can run relatively skinny 32's with almost no modification (255/75r17). When you move up to 33s on stock wheels you def need a lift and spacers front and rear to avoid rubbing on the upper control arm. You will also need to trim the inside lower front bumper and ditch the mud flaps. Depending on the tire you may also need to do a body mount chop, search that term for more info. Bigger than 33's, anticipate all of the above but even more trimming, body mount chop for sure, and probably need an aftermarket bumper. A body lift in the 1.25-1.5 range helps with 33s and up.