Mine are 13.2 on 10s.
If I had to guess,These would be around 14.5 or a little more on 12s. This is the SECTION width, which your outer fender lips will never see on account of this width is around 3 inches down from the tread. What your lip will see is tread width plus the section bulge on one side plus about 1/2 inch clearance to the inner tub or 1/4 inch to the spring. So Ima guessing 13.75. Since the available room is 8 plus 6.75 equals 14.75, you have a full inch to the lip.
Unless you are lowering the body to below the tread surface. Then you will be lip-limited. But most guys run the ride height up about 1 to 1.5 inches HIGHER than the tread surface.
So the way I see it, is borrow that friends 325 and stick it in there!
