You should be fine and you will have a flush look. I believe stock 17x8 are et34, you will not need spacers as that would even push them out further. Because the 18" wheels you mentioned have a et20 in front , thats like running about a 15 mm spacer up front already et34-15 mm spacer = et19. The higher the offsett or et the more the w.heel tucks in and lower = sticks out more. I would run a 235/40 up front and 265/35 out back. The stock rolling dia. for a stock 225/45/17 is about 25 inches, it would be 25.4 for the 235/40/18 and 25.3 for the 265/35/18. hth
volk re30 18x8.5 / tc kline coilovers / cobb ap / afe stg 2 sealed cai / afe air scoops / 5" ets fmic (sold car)
2013 x3 35i fully loaded with M package
Last edited by CT335xi; 01-27-2013 at 02:33 PM.