I finally got my 4" pro comp lift, I plan on running either 35 12.5 R15's or TRYING to run 37 12.5 R15's (if they dont rub)


What should i re-gear the rear end to so it gets the same gas mileage as it did without the lift and tires? An i also probably have to have ford adjust my speedometer. How much do you think it will be off by?

 

I just got 4.56's with 35's, on the way home I was driving at about 45 and the speedometer read about 55 so it will be off quite a bit depending on if you started out with 3.55's like I did or from 3.73's.

 

Check out this calculator.

http://www.4lo.com/calc/geartire.htm