Originally Posted by Irishguy
Originally Posted by AU338MAG
Originally Posted by Irishguy
When you put on larger tires and you calculate your fuel mileage there is a factor you need to also calculate, because you are now actually travelling more miles than what your truck odometer is recording. For instance...

The circumference on a 32" tire = 8'-4 1/2"
The circumference on a 35" tire = 9'-1 15/16"

So if the 32" tires were OEM and now you have 35" tires, every time your tires make one full revolution you are travelling 9 7/16" more distance than your odometer is recording. That really adds up. Which means you're actually getting better fuel mileage than your computer is telling you or your calculations are telling you unless you factor in that additional mileage you are getting with each tankful.
You can recalibrate the computer on newer trucks for a different tire size.

The manufacturers put on the tire which results in the best EPA mileage rating. When I bought new tires for my current truck I put E rated Nitto Ridge Grapplers on it that were the same size as the OEM tires. My MPG dropped by about 3 MPG.


Yeah. I did this on my Jeep Rubicon. I did it mainly to help with the transmission shift points, which still suck, but they suck less than they used to. I think the device to plug in and recalibrate it cost me like $100 bucks or something like that.

I'm kind of a nerd, so just about every time I fill up I take my trip odometer mileage and divide the gallons into the mileage to get the accurate mileage, then I reset the trip odometer at every fill up. This is the only accurate way to check your mileage that I know of. My calculations always show better mileage than the trip computer does.
I do the same. The computers on my last two or three trucks have actually been pretty accurate, but ive had some in the past that could be off by 2 mpg.

Dying ain't much of a living boy...Josey Wales

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