Upgrading to 15" wheels/tires

Just as a point of reference, my '69 Dart is all stock except for the S/S springs. So it sits just a hair higher than stock. I had 235/60-15 tires on 15x7 4.25 BS Cragars and the tires would rub on the inner fenders, inboard and/or outboard, if you hit a bump and were turning at the same time. Switched to 225/60-15 tires on same wheels and the problem went away. I could never imagine running a 255 tire on my car, unless I wanted to start bending/cutting sheet metal.