In my efforts to convert my Z3 1.9 to visual M Roadster specs (grateful for all your help fielding my interior conversion questions), I was worried about the M wheels on my car. Seems like everyone knows that the 2.8 makes the M wheels stick out about an inch when running rear M wheels in the rear of the 2.8. I was concerned because this would not allow me to use real M rear wheels and have to use the 8.5inch wide front M normal-offset rims. Bummer. Upon further research, I found out that the 1.9 rear track width is 1.3 inches wider than the M roadster's, BUT 2.5 inches narrower than the 2.8. Thus, the rear M wheels will fit naturally into the wheel wells on the 1.9 without the protrusion problem of the 2.8 ASSUMING that the owner replaces the original 1.9 fenders+ with the wider 2.8 fenders... which I plan to do when I scrape together some money.