I have a quick question. I want ot put bigger wheels and tires on my xB. The dealer where I bouht my car had an xb with 20's? How can they do that. I know you have to put a lower profile tire, but there is no way that the diameter of the tire to the tread surface os the same as a stock set up. Doesn't this screw up the abs, not to mention the speedometer and odometer? If I get a larger wheel, does my new set up have to have the same diameter to the tread surface as my stock steel wheel set up? Please help?