Is there anyone here runnning 285/70/17's on their truck with a 6" lift? I have the 315/70/17 BFG AT's now and the gas mileage is a little over eight miles to the gallon. Im wondering if i drop down to 285s if the truck would still look good and if the gas mileage would increase? Any advice or opinions will be appreciated.

Thanks
Joel in Iraq 4 now

 

You should not be getting 8mpg with even 37's. I ride the hell out of my truck and I'm getting 11.4 mpg btw, but I'm stock (just a quick fact, and this is really bad mileage for stock). Anyways, I'm assuming you have 3.55 gears with that mileage, have your truck reflashed at a dealer (complain of poor gas mileage and throttle response, etc and your dealer should help you out from what I hear) or order an XCal2, or some other programmer. Many will point you in the direction of Mike Troyer from Troyer Performance, he custom tunes the Xcal2 and your mileage will not longer suffer so badly. I test drove a lifted Hemi (5.7L) on 35's and it was getting 11 mpg. 8 mpg is unacceptable, are you driving over the Alps?

 

is your speedo corected for your larger tires? if not you dont know what your milage is because you changed your final drive ratio with the larger tires you could be getting 12-14 miles per gallon and not even know it because your speedo is of 5 miles or so an hour this will greatly effect your trip and you wont be able to calculate you MPG, good luck

 

No im not driving over the Alps. I have 3.73 gears, Air Raid cold air intake and thottle body spacer, Flowmaster SISO, 6" lift, 315/70/17s BFG AT. Im guessing im getting around 8. But i havent recaibrated my computer for the bigger tires. So i will try that b4 i change my tire size, i really like my 315's.

Thanks for the info

Latr
Joel

 

Remember 315/70/17 is a 34.36 inch tall tire. Depending on what size your stock tires where then you speedo is going to be off showing you are going slower than you really are.

This should be a complete list of tire sizes Ford offers on the current F150's.

235/70/17 - 29.95 inches tall
255/65/17 - 30.05 inches tall
255/70/17 - 31.05 inches tall
285/70/17 - 32.70 inches tall
315/70/17 - 34.36 inches tall
265/60/18 - 30.51 inches tall
275/65/18 - 32.07 inches tall
275/55/20 - 31.90 inches tall
275/45/22 - 31.74 inches tall