285 vs 255 mpg?

Hey guys just picked up a 2012 dcsb 4x4 trd. Truck is already lifted with spacers under the top plate up front and aal in back. Sitting on 285 70 r17 that are e rated. Both ride and mpgs kinda suck! I can deal with the Crappy ride for now, but thought about changing tires to p rated 255 75 r17. Wondering if I'd notice any significant mpg increase?? I'm getting 14-15 mpgs now and I'd really like to get it closer to 17-18 as per the epa ratings. Just not sure if a tire change will help that much.

Thoughts?

 

There are two major factors to how tire size effects your fuel mileage: tire height (which affects gearing) and weight.

255/75 and 285/70 are more or less the same height, so that part is basically a wash. Tire/wheel weight is the biggest factor. You WILL notice a difference in fuel mileage and acceleration (and braking) with a lighter tire. If you don't need an LT tire, get a P rated. The 10-ply sidewalls of an LT add a LOT of weight that you most likely don't need unless you haul/tow a lot or do serious off roading.

Here are some of the lightest tires I have come across while doing research for my next tire purchase:

Hankook Dynapro ATM:
265/70/17 - 39 pounds (P) (I currently have these on my truck and I LOVE them, all-around fantastic tire on- and off-road)
285/70/17 - 61 pounds (LT)

Falken Wildpeak A/T3W
285/70/17 - 51 pounds (P)

Goodyear Wrangler Duratrac
285/70/17 - 54 pounds

 

And I think rolling resistance also factors in a minor way. All else equal using a narrower tire will improve mileage.

 

Rolling resistance is a small factor, but wind drag of a wider tire actually has more affect. If you have two identical tires, with the only difference being width, they will both have the same total amount of resistance/friction over the contact patch, it will just be spread out more with the wider tire.

 

This is what I was thinking. The 285's on the truck are 55 lbs, the ones I want are 39 lbs. I knew height difference would be negligible, but hoping less weight would help. Just wonder if it's going to get me 2-3 mpg. Not sure it will, and it's not worth dumping the money into it right now since the 285 look to be brand new if I can't get at least 2 more mpg.

 

FWIW, I consistently get 17-18mpg with my truck with the 39lb 265/70 Dynapros.

 

Same in the winter. Closer to 20 in the summer though

 

I have 255/75/17 DuraTracs (I think they're about 41 lbs) with 2" lift and I really like the tires...getting around 16-17 city 18-19 hwy.

 

255/75/17 are essentially the same diameter as a 265/70/17 , not a 285/70/17

Maybe you're thinking 255/80/17 which is a 33"

 

Thanks for the replies. Its good to know that my idea might actually yield the mpg improvement I'm looking for. Oh and get rid of the rub on the uca that would be nice too.

 

Yes, that's exactly what I was thinking of.

 

Cooper AT3 255/75r17 is 38#