Im currently running a square set of 18x9 oem M3 wheels with 225/45/18 front and 255/40/18 in the rear. I went to a tire shop today and asked the salesman about getting 255/40 /18 in the front to match the rear. He said its not a good idea because it would probably rub when I turn. That fine, so when I asked him what would be the perfect square tire setup, he made a phone call. As per the person on the phone, on an XI, I should not have 18x9 it must be 18x8 with 225/40/18 all around and if I stay with 18x9 he wouldn't recommend any tire size because it will mess up my differentials. How true is this?? Any feedback would help....
