245/60/15's on 15X8 rims

68 Coronet RT said
Getting ready to purchase my new rims and tires for my 68 GTS but not to sure what will work on the rear. I'm looking at 245/60/15 on a 15X7 or 8 inch rim or 255 60/15's on a 15X8 inch rim. Suspension is all stock except air shocks right now but plan on taking them off and putting regular shocks on and adding a leaf spring to raise the back end. On the left side I have 11 3/4 inches between wheel lip and inner fender and 12 inches on the right side.

SBP 8 3/4 in that GTS right?

Keep in mind you don't get to use all of the space from the inner fender to the quarter lip if you have the leaf springs in the stock location. You end up losing at least a 1/2", probably more like 3/4" out of that with the stock spring locations. So, really you should only figure on having about 11", because that's what you'll have on the left side.

That makes a 255/60/15 kind of tough. The BFG T/A's have a section width of 10.2" when measured on a 15x7.5" rim (manufacturer spec), which is on the rubbing side of marginal clearance. Now, on a 15x7, you might end up closer to 10" with that section width, which would give you enough space assuming everything is centered up with the backspacing properly.

I think the 255/60/15 on a 15x7" is about as much as I would try, even that tire on a 15x8" might not work. A 245/60/15 would be a safer bet, run it on a 15x7 with 4.25" of backspace. With a SBP 8 3/4 you might also be able to get away with 4" of backspace, with a BBP 8 3/4 you'll definitely want 4.25".