Hey,
I'm currently running OEM M5 wheels on my 650xi GC, I didn't run the M6 wheels because the rear's are much wider and being that the wheelbase on the 6 series is adopted from the 5 series I just went with the M5 wheels. I'm currently stacked with 295/30-20 in the rear it sticks out a little, can I go down to 285/30-20 without issue? I'm going to lower my car and the wheels are going to rub in it's current stage.