Re: Tire sizes
A 275/55R20 will fit without any rubbing. I might be mistaken, but I think anything bigger than that will rub. Also, the speedometer will be off a little bit due to the slightly larger circumference of the tire.
Current: 2015 Jeep Grand Cherokee Summit 4x4 -- Granite/Dark Sienna, 5.7L HEMI V8, Platinum Series Group, Skid Plate Group
Past: 2014 Jeep Grand Cherokee Overland 4x4 -- Granite/Beige, 5.7L HEMI V8, Quadra-Drive II, Advanced Technology Group