Quote:
Originally Posted by mcrews
actually dave, quite a few have.
As a general note, frank lee commented that trucks doent see a benift.
But the trick to the equation is how much highway miles you are driving vs city driving.
Also you cant be going from 15 rims to 17 rims, because then the issue is the extra wieght. But a 4-7% increase in diameter (given hwy driving) absolutely will result in betterr mpg.
Just common sense alone would have to question your 1 in 10 statement.
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My "1 in 10" statement was directed at pickups. I know Big Dave tested different things, including putting an overdrive and 3:03 gears in his truck. I can't remember the particulars, but he found worse FE with larger tires. I've heard similar from other truck owners.
I do agree that the benefit (or lack thereof) would depend on city/highway mix as larger tires/rims add extra weight and rotational mass. That would likely lead to a decrease in FE in city conditions. Also, the gearing benefit would not show up much in city driving, as you're not in top gear much anyway. Of course, putting taller tires only on the rear would contribute only half the additional weight/rotational mass, while giving you all the gearing benefit.
My thinking is that taller tires only on the rear would also have little affect on aero (maybe even a slightly positive one?).