The wheels I have are 17x8 with 4.5 inches of backspacing. My 265/70 R17 tires were about as close as you can get to even with the fenders. My current 315 width stick out about an inch.
2010 JK, Red Rock Crystal, 6 speed manual, Ripp supercharger, 4.56 gears, OX lockers with electric actuators, Rugged Ridge XHD front and rear bumpers, Warn M5000 winch, Rugged Ridge Side Armor Guards, Rugged Ridge Front Skid Plate, Rugged Ridge Evaporator Skid Plate, M.O.R.E. Oil Pan & Transmission Skid Plate