Mounting larger-than-stock tires on stock YJ 15x7 wheels causes tire contact with the springs and sway bar. Stock backspacing is 4 1/2 inches. Many aftermarket wheels use 31 3/16 inches backspacing. That means at least 1 1/16 inch more clearance for larger tires. And the real clearance gains are often greater because sidewalls don't bulge as much on 8- or 10-inch-wide wheels.