Personally I was running an 18x9.5 with a 35mm offset in the rear with a 235/40 series tire with minimal rub. At a 45mm offset out back you should be close, with maybe some contact. Mine was so close without rolling the fenders I had shaved sidewalls. I also ran an 18x8.5 out front with, I think, the same offset or 5mm less with a 5mm spacer to clear the coil-overs, and 225/40. My car is a E46 323i Sedan.
current rides (my wife and I):
2002 Volvo V70 XC Cross Country Wagon, 2004 Volvo V70R, 1985 Buick Regal Grand National, and My Desk.