Has anyone compared their mpg's with the stock rims versus aftermarket rims? And what size rims did you replace them with?

 

There's definitely lots of info on this in the Wheel and Tire subforum but you basically want a wheel and tire combo that weighs less than the stock setup in order to observe an increase in gas mileage. The consensus here is that the stock steel wheel + stock tire weigh about 44# together. Wider tires might have more friction, but I'd bet they also have less rolling resistance so I'd consider friction/rolling resistance fairly negligible. Just keep it under 44lb per corner.

 

So obviously lighter = faster. Everyoe also says larger rims will slow you down. I have personally been wondering though if you managed to get a lighter weight 20in rim if the difference in circumference would balace out the slower acceleration. I dont disagree that your wheels will accelerate slower, but has anyone ever measured this against the difference travled by the larger rim?

In response to the question at hand though, your mpg will drop according to the cars calculations. It wont compensate for the larger rim and read slower on the speedo. Even though your going further each revolution of your wheel it will still think you've traveled the same distance while burning more gas.

 

it isn't just the bigger wheels, but the bigger rubber needed to wrap around those big wheels and also adds to the weight.

also, you have to make sure to calculate the difference between stock and aftermarket setups because your speedometer and odometer wil be off.

also, more friction means more traction, which also means more roll resistance.

 

as has been mentioned, the size of the WHEEL doesn't matter all that much. it's the overall diameter of the TIRE that matters. by going to a larger diameter, you're essentially 're-gearing' the drivetrain. so, in theory, a larger diameter tire should mean better mileage.

BUT, there's a bunch of other factors going on. the weight of the wheel/tire combo will gave an effect for sure. all that extra rotational inertia will offset any gain from the larger wheel in a hurry. for that matter, i would THINK that even if the wheel/tire combo weighed the same as the stocker, any sort of stop-n-go that required a lot of acceleration would wipe out any gains you would see from the larger setup. prolonged freeway trips would likely benefit, though.

Mike