5.5" backspacing puts the wheels right up to the quad shocks. You can still fit several sheets of paper between the wheels and the quads at that point. If you havent already, you can also reverse the quad shocks if the big part is towards the back and make a little more room for wider tires. You can go in another inch or so if you're not running quads, and out a little more if you're running small tires because they still wont stick out. Tire fittment also depends on what brand exhaust you have, IF you have tailpipes.