[Hotrod70C10]

I'm about to go drop some money on a set of Bfgoodrich radial t/a's. I currently have them in 255/70/15 I want to keep that size on the back and change to a smaller sidewall on the front. The next down in a t/a tire is 255/60/15. How tall is that from tread to tread. I don't want to spend a bunch of money and not be happy with it. Thanks in advance. Billy