First off, it depends on what year you have. The newer trucks are easier to get bigger tires under than the older models. I had an 08 lariat super crew 4x4 (what I'd consider newer) and ran 2.5" leveling up front and 1.5" add-a-lead in the rear. It was perfect on 35's with stock wheels and 3/8" spacers. I ran it that way for at least 25k till I sold it. Great truck with decent mpg.
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2012 Flame Red JKUR- Manual w/ 4.10s & Nav
JCR Front Pre-runner & Rear Dagger, RK 2.5" Flex System, Bilstein 5100s, Teraflex Exhaust Spacers, Nitto Trail Grappler 35x12.5x17 Tires, Black ATX Slot 17x9 Wheels