Here's the review I looked at on these tires, actually one of several:
http://www.cartest.ca/successful_yokohama_winter_t.htm

Glad to hear that you got it sorted out. It would seem that Ford made the front brakes a little bit larger than previous years on the 11 GT, and the 17" steels we used to supply for those cars no longer fit.

For any 2011 V6 people reading this thread, you're still OK with 17".


cheers
Ed N.