Originally Posted by JAJ
I measured mine just after I got the car. I don't have my notes handy but I recall a radius of 210mm plus clearance (say 3 to 5mm) so that the barrel of the rim will clear the the front caliper. That means the barrel inside diameter has to be more than 16-1/2 inches. I don't think you'll find a 17" rim with that large a barrel diameter. The barrel has a trough between the beads so that the tire can be pulled over the outer lip during mounting, and the depth of the trough makes the barrel smaller.
The rears are easier - I had a set of BMW Type 49 17" rims for my M5 snowtires and they fit in the rear. The Type 49 is one of BMW's largest barrel diameter 17" rims and they were definitely no-go up front - they were way too small.
thanks for the helpful info!
I measured the inside rim diameter and it was close to 15-3/4 inches. So it doesn't sound like it would fit ;(
The rotors up front on the M3 are already 360mm - so that combined with big caliper make it a no-go. While the rears are 350mm with a smaller caliper - making it possible.
Time to find 18's! Thanks.