i want to downsize my wheels to 16's and increase the tire sidewall, and was wondering how big could i go in this matter, my concern is tire rub. the reason i ask is i have a friend who is pulling his oem tires and wheels from his mustang and would be willing to sell them to me for 100 for all 4 wheels and tires. the set up is 215/65/r16. any help would be appreciated.