I talked to the guys at the BMW winter tire program and they recommended Continental ContiWinterContact TS790V tires. I have 18" stock wheels, so they recommended 17" wheels. You can buy from BMW these tires and BMW rims (style 68). It's the same rim all the way around (7.5”x17”) and tire (225/45/17) but the offsets are different - front, 47; and rear, 25. The special I got from BMW Arlington was $340 (rim+tire) for each corner. I haven't put them on yet - but it's going to snow on Wednesday so I guess I need to put them on soon!