[Eli]

I have an supercab/shortbox 3.73 geared truck I drive with about 1,100 lbs of stuff in the back. Will the taller 20" wheels make much difference in fuel mileage (effectively higher geared)? I will be keeping the truck and could use my stock 17's for snow wheels.....

 

[fireguywtc]

may lower the milage slightly. But I doubt enough that you would really notice.

 

[kiley]

If you get 275 60 20s, they will be really close to the same height therefor will not change ratio. The weight of the tire and wheel combo should be the only thing to effect your mileage, and I don't believe it will make much difference. The price of the wheels will be much more, same with the tires if you go with 20s.

 

[SteveHeywood]

If you get 275 60 20s, they will be really close to the same height therefor will not change ratio. The weight of the tire and wheel combo should be the only thing to effect your mileage, and I don't believe it will make much difference. The price of the wheels will be much more, same with the tires if you go with 20s.

EXCUSE ME! A 265/70-17 is 31.7" in diameter, a 275/60-20 is 33" in diameter. The 17 turns 657 RPM vs 630 for the 20". A 275/65-20 is 34.1" in diameter and turns only 610 RPM, a big difference for a 6.0.

If you're looking for mileage swapping a 265/70-17 for a 275/65-20 MIGHT increase your mileage, but maybe not. I know from experience that my 05 6.0 was geared near perfectly for towing an 8,000 lb travel trailer with 265/70-17s & 3.73 gears.

 

[Eli]

If you get 275 60 20s, they will be really close to the same height therefor will not change ratio. The weight of the tire and wheel combo should be the only thing to effect your mileage, and I don't believe it will make much difference. The price of the wheels will be much more, same with the tires if you go with 20s.

The 17's are 31.7" high and the 20's are 34"....there is a difference. TireRack has a wheels for around $200 each and tires for about $165 each....not too bad.

 

[kiley]

I stand corrected!!! I was looking at 275 50 20s. EXCUSE ME!

 

[popups4rent]

My 285/75R20 took about 1 mph off city and 2 highway, but they also went with the lift. If I had a lot of cash I would like to run 17" wheel with 35" tires to see if I get any mileage back.

 

[Eli]

My 285/75R20 took about 1 mph off city and 2 highway, but they also went with the lift. If I had a lot of cash I would like to run 17" wheel with 35" tires to see if I get any mileage back.

I assume you recalibrated the speedo so it was a true 1/2mpg drop?