18x8 +50 offset rubs in the rear with 225 wide tires. You could probably get by with 215 wide tires however.
Basically when buying wheels for the 6, try and get as high an offset as possible. If your caught between two wheels, and one is +48 and the other +42, go for the +48. It makes a big difference, especially if your driving aggressively.
Plan to roll your fenders with +42 offsets greater then 7 wide, or any 8 inch wide wheel.