Dan -
Don't know if this is helpful for you or not, but I ran 255/60x15 Goodyear Gatorbacks on 10" PSE (FIA style) rims
on the back of my ERA FIA with no issues. I eventually swapped them out for a set of the 305/50x15 T/A's.
Here it is with 245/50 Goodyears on the front, and 255/60 Goodyears on the back:
and here it is with 265/50 T/A's on the front, and 305/50 T/As on the rear:
Jeff