BamaTJ

Anybody have any real world experience with this good or bad? I have 4.10 gears and 285/70/17 KM2's currently. They don't have much life on them and I was thinking of going to a 315 to drop my RPM's at cruising speed. Truck already has leveling kit so nothing to change to fit them. I spend probably 80-85% of my time on the interstate, very little stop and go driving but definately do it some. Any ideas or opinions on this subject? Is it just a myth or will it really help me pickup some MPG or will the larger rolling mass just suck more fuel?

hardtarget870

I think you have the right idea, but 315 is the tire's width and yes if you keep the same aspect ratio, the 70, then you would increase overall diameter but why increase width if all you want is diameter. Only because it would be more labor to turn the larger tires. you could keep the 285 or round-a-bouts tire and just increase the aspect ratio to 75. More diameter without adding too much more mass.

Guardrail

My mileage didn't change when I switched to 315's. It might have went down a tad. The increased rolling resistance negates any gain in gear ratio.

97DodgeRam

255/85/17 might help out your mileage. They ought to be around the same height, but narrower which should lower the rolling resistance.

Dodgezilla

I have experience with this. First off the difference will be minimal from 285s to 315s. Your in-town mileage will likely go down but your highway mileage will probably go up a tad. 315s definitely look better but you may feel a slight loss of power....

BamaTJ

Yeah I have to stick with the BFG tires cause I am in their race program and they are much cheaper for me. I will look into the 255/85's and the 35" since they don't make a 315 KM2 for 17" rim. I just don't want to lose mileage by going to bigger tires, I am fine if it is unchanged.

Guardrail

They do have the BFG All-Terrain T/A KO in 315's. If the price was right, I'd go back with them. The performance was great, the tread life just sucked.

AH64ID

I went from 285/70 to 255/80. They are 4lbs a piece lighter, 11 fewer rotations per mile, and about 150 less rpms at 80. I haven't noticed a change either way, but I haven't had them on long enough to really see an increase.

I think tread life on any AT or MT is going to be crappy, all the tq these motors makes eats the rubber up.

15 Digger

I went from stock to 315 Mt and had 200 rpm less on highway but about same mileage. 315 are wider and heavier so one equals out the other. The ride was better with the bigger tires but so was the wear on front end. Trade offs you have to decide on.

skindaddy

AH64ID how's the 255/80 look on the truck?, not familar with that size

Raspy

There's a lot more to mileage than tire diameter.

I ran a set of BFG 315/70/17. I lost about 1.5 MPG with them. They are harder to roll and have more wind resistance. The truck was better off road, but worse on uneven paved roads as the tires steered it much more than the stock 265s. Towing was a lot worse with my 3.73 gears. After they were worn the truck pulled severely to the right. Constant balancing was needed.

Then a set of BFG 285/70s went on. Good in the snow. Better mileage than the 315s but not as good as stock. Very weak tires that are easily damaged and like riding in inner tubes. Blew one out on the freeway after a small slice in the sidewall rubber (not the cord, just the rubber). That's when I swore off load range D.

Switched to 285/75E Toyos and, finally, to 285/70E Toyos. Got the best of all worlds. Stiff tire, good mileage and bigger than the stock 265s. A real high quality, round and easily balanced tire.

Maybe not what you want to hear, with your connection to BFG, but BFGs are not worthy of being on my truck. The 315s will fit with or without a leveling kit and will only rub at full right or left turn.

AH64ID

Essentially a 33x10.50. Narrow tread at 7.5".














Yep, I am running a taller, lighter, narrower tire at more pressure and the mpgs haven't appeared to change much.. mainly because I went with a MT.. even thou the rest of the equation means easier rolling, the tread pattern makes the biggest difference.

GlennRMK

Now those are some pizza cutters!

They would be perfect for a dually though.

I changed from 285/70R17 BFGs to 35x12.50R18 Toyo MTs and really didn't see much of a mileage change with my 3.73s.

For ideal mileage though, that size, or 285/75R17 or 295/70R17 is probably ideal.

Danderson

Let's start a petition for a 275-80-17 AT or whatever. E-rated. I'd be 34" tall and a bit narrower than a 285. We know fuel's going to go up again and this size might work out great and fill up those wheelwells.

1buck4me

i have the new goodyear dura trac's and i love them. i have 410 gearsand an automatic tranny. the tires are a 315/70/17d rated. the weight on them are 3195 lbs per tire at 50 psi. my old pro comp extreme allterains e rated were the same weight at 65psi. the new ones ride so much smoother and quiter..i tow a 12000 lbs toy hauler and they tow and feel good. the pro comps were a 305/70/17