Anyone know the size of the stock Mini GP wheel?
I thought it was 18x7 with a 52 offset but after measuring with the tire still on I am not sure. It seems like the wheel might be 7.5 wide or be less offset than 52.

 

I don't know the offset, but they're supposed to be 18x7".

Keep in mind that those numbers are taken from the place where the tire bead seats, not the overall from the wheel. I've got a new set of R99s (17x7") in the boxes, and they measure about 18-1/4" overall diameter and 7-3/4" total width.

 

Normally, a wheel will have the size and offset stamped somewhere on the inside (not the part hidden by the tire). Take a close look.

 

This is 100% correct. Wheel width is measured on the inside of the wheel. Bead to Bead. So you really do have wider wheels than you think!