Quote:
Originally Posted by 4skrunner
Looking to get some new tires this summer and I’m contemplating size vs weight. I currently have heavy mt tires and wish to gain some mileage back. What I’m proposing is a change from:
285/70/17 Falken wildpeak mt load C 32.8” 62 lbs
To:
285/75/17 Firestone destination xt load D 33.9” 53.7 lbs
So gaining about an inch in height but losing about 8 lbs per tire.
Any speculation as to what effect this new taller but lighter tire would have on MPGs? Stock gears.
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For your size change you may be saving weight but you are relocating the weight at a farther radius. IE less weight but increased inertia which counteract each other in terms of mpg changes. More inertia means more resistance to rotational acceleration.
It will probably feel a little less slugish during acceleration and breaking with slightly lower rpm ranges once you are up to speed. This is un-sprung weight savings which most people agree has a significantly larger impact on mpg than sprung weight reduction. I agree with most others here that think you will see no overall mpg change.
For reference those C load wildpeaks are pretty heavy because Falken developed them as one of the stock sizes for the Jeep Galdiator Rubicons when they first came out. I ran a set of their ATs in the same size and took a hit to mpg after that.
I switched to 255/80/17 wildpeaks after that set which is around 8 lb savings per tire. Almost no difference in mpgs
I do love the 255s on and offroad though. Just taller than the 285/70s and it feels much lighter driving around town. Much better in snow and slush, the 285s wanted to float too much. I will probably stick with this size or go to 34x10.5 next.
