I am running 17" rims on the back of my 51 Plymouth. P255/50R17 Hankook Z rated tires, I don't need the Z rating but I do want the improvement in traction and handling. I am using a set of new stock steelies for a 2008 and up Charger, Challenger for the rims. Pretty cheap from RockAuto, Dorman 939137. Probably not cheaper than just new 15" Cooper's, but Coopers aren't really performance tires and in my case 255's were never going to fit the stock 15" rims..
Clearances are good, I came up with a way to sort out how to figure max tire size without having to buy tires, mount them and see.
http://www.yourolddad.com/tiresComparison between stock tire (middle one) and the replacements I went with.
