We wanted 37s but only 4 inches of lift on our J-20. Fortunately, most FSJs have huge inner wheel wells that easily allow bigger tires with a little trimming here and there - the J-Trucks and Cherokee Chiefs more so than the four-doorWagoneers. After measuring and drooling over cool wheel designs, we found we could best fit the molded 37x12.50R17 BFG Krawlers on Wheel Pros Moto-Metal black 951 17x9s with 4 1/2 inches of backspacing. We also whacked off the rest of the ugly flares with a reciprocating saw for a cleaner look. The rear flares had to be cut for the 37s regardless of the backspacing used. However, we could have easily kept the flares all around (had we wanted to) by going with 35x12.50 tires on 8-inch wide wheels with 3 1/2-4 1/2 inches of backspacing (the more the better).