Originally Posted by hsiaochinsan
Maybe we should look for rims that fit the stock 20" tires. I can do tires swap and save at least 2G on tires.
We could build you a set of 20's to fit the factory sizes and have them built a bit flusher to the fenders to fill in the gap. Or we can go a bit wider to our standard non rub fitment so you can have wider tires on there!
As for 21's on an F10 M5, you can check out this thread: