What is the largest diameter tire I can put on my x5. I want to make my truck a more capable off-roader. Since a lift doesn't seem like an option I feel like the only direction I can go are A/T tires. At the moment I have 255/55/18's could I get 255/70/18's and throw them on my truck? Im guessing this would mess with the computer/speedo. Is it possible to recalibrate the computer to compensate for a larger wheel? Thanks for all the help!