I am thinking about purchasing some BBS RSII 18" wheels, 8.5" Front, 10" rear. Tirerack representatives have told me in the past to go with 235/50 and 255/45. Other sources have told me that 255/45 and 285/40 sizes will work. Is the tirerack suggestion due to concerns for a fender lip roll? The 95 740i (E38) fender differs from the 94 in that the fender does not overhang the wheel. Shouldn't this allow wider tire size than what tirerack recommends?