I currently run 35x12.50's and on flat highway with the wind behind me I can see/get to 57-60mph with the 2.5 and 4.10's. I had 33x10.50 BFG KM2's before the 35's and it was much more bearable. I am also a broke college kid, and can honestly say bigger tires were not my savior as my YJ doesn't see much of anything other than pavement (currently). The 33's I could push it to about 60-65 and use 5th. When it was on 33s I drove 50 miles round trip to work each day, filled up about twice a week, and got right around 14-15mpg. I have a 4.0 throttle body, ford 19lb injectors, and an ARB Snorkel. Hope that helps you some, let me know if you have any other questions!
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