Does anyone know how much backspacing I would need on 33x12.50 on 16x10 wheels with a 4" suspension lift for my wrangler.
thanks  

an 8" wide wheel will be better for the 12.5's for handling and keeping your front end alive longer, most tire manufacturers recommend using 8"ers with 12.5 wide rubber.

4.5 is best for mostly mild wheeling, with the sway bar disconnected the front can contact the shock/spring tower in extreme articulation... 3.5 recommended for hard core..

also the 5" backspaced Rubicon wheels can be used, though same as the 4.5 up front and in the rear there is very little room for the sidewalls, they can get sliced on the rear spring pads....


this is a pic of stock rubi wheels with 1" spacers making 4" backspacing...



here is what can happen with 5" backspacing and a slightly misaligned rear track bar




my 2.5" HD rancho lift on 34x12.5-16's....