Larger circumference tires better mileage?

[joe_julie81]

I am wondering if this could be true. I ordered my dually with the 4.10 rear axle for more power pulling the heavy 5th wheel. At 70 mph I'm over 2000rpm. Now that I'm getting a TC I don't need that much torque. But I don't want to change the rest axle. So would bigger circumference tires get better mpg at top end? I have 235/R80/17 now. If the answer is yes, what size would be recommended?

[Kayteg1]

I ordered my dually with 3.55 differential for fuel savings and setting CC at 60 mpg on last 10 fills. what was 99% with 6500lb camper- my average is 12.3 mpg.
My trucks pulls 18,000 lb sets on 5% grades without downshifting.
Compare to what you have.
Aerodynamics are pretty tricky subject. Typical myth that lowered tailgate increase mpg was busted by Myth Busters.
Still they used 1 model of pickup and on different model it can be other way around.
Still if aerodynamics would play big role on the road, we would see more of those aerodynamics semi-trailers. I observe them on the roads and only few are using foldable tail wings.
Evidently not enough difference to go into hassle.

[Axle]

From a physics perspective a larger diameter tire would have a greater rotational mass inertia. Therefore it will take more energy to accelerate them as compared to a smaller diameter tire. Thus larger diameter tire should get less mpg and result in increased brake wear.

[yblaw]

I just ordered 255/70R 22.5 tires and wheels for my Dodge Ram 5500 that's going to increase my tire diameter from 32" to 37". I'll let you know on the mileage after I get them mounted.

[Rustofer]

My experience too, is that larger tires (on the same size wheel) have worse dynamics that increase fuel consumption, in spite of their larger circumference. I see you already have very tall tires (80-series). I would think you might get a slight fuel saving with lower-profile tires on larger wheels, but likely never enough to offset the cost of them. And keep in mind that at highway speeds the largest contributor to fuel consumption is wind resistance. Many TC's have similar frontal area to 5'ers.

[Ski_Pro_3]

A taller tire will reduce rpm's at a given speed. However, the taller profile will cause more drag at higher speeds, most likely mitigating any mpg reduction due to the lower rpm's.
A taller tire also usually has higher tire pressures. That might help mpg. But they weigh more, so that might lower mpg.

[rexlion]

I think the mpg advantage would be slight. But it can be done (and keep in mind that your speedometer reading will then be off). A tire store could advise you, too.