This has to be the most discussed topic in the wheel and tire forum.... I would get 255/35/19 and 275/35/19 for ZCP wheels. It maintains the factory stagger in width and diameter, plus those sizes are well-suited for 9" and 10" wheels. I wouldn't hesitate to change to those sizes. The OEM sizes are a little stretched on the wider ZCP wheels. You will also fill some of the fender gap if you are on stock suspension (slightly taller tires). I personally don't like the idea of 285/30, 255/35 combo because the rears will be lower profile than the front and that is how your car was programmed. Best of luck and do yourself a favor and run a search on this topic if you want more information.
'13 M3 - Silverstone II - Sold
'04 M3 - Jet Black - BBS E88, KW Clubsports