[bm5bullit]

Don't want to sound like an expert or anything but, there is a lot of info on the E60 M section about this. I can tell from experience that the options are much greater when you try to find wheels/tires for the 17/18 inch sizes than you do for anything larger than this. The only disadvantage is that you can only use the wheels/tires at the track since they won't match. A set of used 18 inch wheels and some Hoosier or Mickey Drag radials are half the price, or less, than any 20 inch wheel with tire combo.