i have to grind my rear calipers, which are from a 3/4 ton front end and the RuffStuff brackets. I'm also running the 3/4 ton rotors.. the wheels i run are 15x12 with 4" back spacing. I was going to run a spacer to make the wms the same as the front which would also allow me to not hit the calipers, but as of rite now, i have to grind them