2006 Silverado 4.5 RC lift w 285 70 17

[mountainguy78]

Im the new guy here, please bear with me. I just recently lifted my 2006 Silverado with 4.5 RC suspension lift. After the lift I put on 285 70 17's BFG KO2 and am rubbing the washer bottle either in full right turn in a dip or while in reverse. RC said those tires should be fine. I imagine my backspacing and or offset is off. Just wondering what it should be, or what's max offset/backspace on the wheels I can be at without rubbing? Thanks