hello, I was wondering if any one knows the best size tire to run on a 6.0 powerstroke?
I run a 265/75/R16, running stock at 55 my lie o-meter tells me I'm getting 22 mpg. at 65 I get 19.5 mpg with the lie o-meter. I've hand calculated it after long trips at 70-75 mph through the mountions here in alaska and only get 18.5. I was thinking about getting a biger tire for my truck but cant decide witch one to go with. I'm thinking about a 295/75/R16 AT KO tires. I beleave this would help me get the best fuel economy at 60-65 mph, witch would be great.
I currently have electric fans instead of the clutch fan, sct livewire tried multiple tunes, blocked off egr, 4" exhaust cat back.

 

The 265/75 R16 tire is about 31.5" , the 295/75 R16 is like 33.5" in diameter. This means that the smaller tire's one rotation is 6" shorten, then the "big-one". 99" vs. 105" to be exact. It wouldn't be a big difference if we are talking about only one full turn, but at like 1000 full turn of the tire is 6000 inches, what equals about 500 feet difference.
Anyways, the bottom line is, that you could run the same speed with a lower engine RPM, what would help the fuel mileage on flat land. But there is a significant advantage of the smaller tires in the mountains.
In your case, there is a chance that you'll get better mpg with a bigger tire, but it's not necessarily true - due to the mountains.

 

I went from stock 2657017 31.8"to king ranch stock 2756520 34.1" tires.
your highway cruising mileage may go up max like 1mpg but mountains snow on the roads and towing will diminsh the gains of taller tires by placing more load on the truck. your around town mileage will also go down. i noticed a loss of power with the taller tires obviously theres enough power but there is a noticeable drop. also the wider tire will hurt mileage compared to the same height skinny tire. also being in alaska the wider tires are worse for winter driving. if you get taller tires dont forget to recalibrate your speedo or at least realize it will read slower than your actually going.

 

Aw, at least 35's, preferrably 37's

 

Now this is just my experience, but I have yet to see bigger tires get better mpgs. Not once. MPGs is also one of those tricky calculations that it's way too individual. In other words, you can have 10 people say that they saw an improvement with bigger tires(which I can't reconcile in my mind how that would be true and I've heard the bigger reasons why and a problem is that people tend not to do just the tires, they do something else that could have helped with with mpg as well, alot of variables) and yet you still may not, because factors may not be the same. I have yet to hit the average mpg that the vast majority of people with DRWs claim when I was stock or modified. That's one of the reasons why I tend to put very little faith in mpg claims.

If you are really concerned with mpg in these big behemoths then just slow down. That is the simplest and cheapest thing to do and it would atleast the same improvement that you would have seen with bigger tires(which like I said, I'm still iffy on). You might have to leave a little bit earlier to get somewhere, but you'll get your improvement as long as you don't have some quirky driving habits.

 

Tall yet skinny tires will yeild the best economy, I think there is one tire with an 85 aspect ratio, that would be the way to go.

 

235/85/16, going narrower will help, going taller can help if you have low gears.

 

Thanks for everyones replys I probably think about it a little and make my choice.

 

I have to agree w/ Tex. Going to a bigger tire will not get you better gas mileage. Going to a wider tire will decrease your mileage.

Increasing your tire pressure will help a little and cost you nothing...

 

cartman's got it down.
235/85

 

the bigger the tire the hevyer

 

yup. with my 3.73's, i went from the stock size 235/85R16, firestone transforce A/T's to 265/75R16 general grabbers and lost a good 1 MPG on average.

or, put it this way. i drove to NY from my home in june 08 on the firestone 235's. i averaged 20.3 MPG driving 67mph (just under 2000 rpm on the tach), and used grey bottle diesel kleen. wife and i drove back out to KS the week after our wedding in june of this year. same weight cos we had about as much crap in the cab as i had on the way up there. same driving style. 67, using diesel kleen. only difference was it had the general grabber 265's on it. average economy was 19.7.

i have noticed a bit more of a difference in shorter trips and/or city driving. i plan on going back to the narrower tire size for my next set and after this last change just to a wider size, there's no way i'll go to a 33" tire, which i thought about for a bit.

the other thing to consider is what kind of TREAD you have/want. i went from a more highway tread to a more aggressive tread. if i can get general to pro rate a new set (they're wearing FAST), i'll try the same grabbers in 235/85 to see what they do. or i might try the transforce in 265. i had good luck with them the first round, and can be bought locally.

 

235's street tread and run them a little hard.

 

I was just kidding

 

Manf. probably spent a fair amt. of money figuring out which size would give them the best mileage per vehicle. I will stick with what came from the factory. 265/70 R17.