My fitment with MPSS tires:
18x8 ET45 with 235/40/18 up front without rubbing
18x9 ET48 with 265/35/18 in the rear with light to moderate rubbing on the joint between the rear fender and the bumper. A 4mm roll on either side eliminated 98% of the rub. A 255/35/18 would fit perfect.
Stock height 2010 MSport 135i.