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Axle Ratio, tire size, and final drive ratio ?s

I have a very large Dodge one ton truck that I sometimes have to drive to work. The truck has a 4.10 rear gear ratio, which pulls great, is not gas friendly. I was wondering how tire size might affect the final drive ratio, say if I went with taller tires, or shorter…not sure which will do what. Any ideas? Thanks

Taller tires (greater diameter) will effectively lower your numerical final drive ratio. However, there are other factors involved in fuel economy, so you won’t see a proportional increase. You might even see a decrease.

As a matter of fact, too often the axle ratio “number” is mistakenly looked at seperate from the wheel/tire number. The old Ford 4.11 rear ends made stump pullers of the cars they were in but they had 7.00x15 tires which look miniscule compared to the tires on a late model truck. Engine RPM/road speed is the important ratio.

The small differences that a tire diameter would make (and still fit in the fenderwell) are not worth mentioning. Don’t forget, the speedometer accuracy would also be affected.