I dont know if thats the right way to go about measuring for wheels. I have TTII's 17x8's all around with 4.75 backspacing. I would say there is less than 1/2" difference and thats just at the middle of the spoke. What kind of brakes are you planning on running and that may be a better way to figure out what you need. I am running 4 piston wilwoods in the front and 97's in the rear.