I was told by my local Chrysler dealer that they can reprogram the on board computer to compensate for tire sizes. I have an add on box that compensates for my larger tires, but I didn't know of the dealer ability to reprogram at the time. If it's under warranty like the newer Jeeps, you can ask. Maybe they'll do it for free.
^PTaylor, they lied to you. They can't do anything more than stock sizes and one or two uncommon non-stock sizes (edit- the European tire sizes, I'm told). They can't do 285/70/17, for instance, 265/75/17, 33", or 35" I know for a fact- Mark W.