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

**URL:** <https://community.cartalk.com/t/axle-ratio-tire-size-and-final-drive-ratio-s/16542>\
**Category:** Maintenance/Repairs\
**Created:** [July 11, 2008, 11:57am UTC](https://community.cartalk.com/t/axle-ratio-tire-size-and-final-drive-ratio-s/16542 "2008-07-11T11:57:19Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Benzfannc](https://avatars.discourse-cdn.com/v4/letter/b/e9c0ed/32.png) [@Benzfannc](https://community.cartalk.com/u/Benzfannc)\
**Post date:** [July 11, 2008, 11:57am UTC](https://community.cartalk.com/t/axle-ratio-tire-size-and-final-drive-ratio-s/16542/1 "2008-07-11T11:57:19Z")

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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

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**Author:** ![NYBo](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nybo/32/17281_2.png) [@NYBo](https://community.cartalk.com/u/NYBo)\
**Post date:** [July 11, 2008, 12:35pm UTC](https://community.cartalk.com/t/axle-ratio-tire-size-and-final-drive-ratio-s/16542/2 "2008-07-11T12:35:02Z")

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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.

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**Author:** ![Rod-Knox](https://avatars.discourse-cdn.com/v4/letter/r/a183cd/32.png) [@Rod-Knox](https://community.cartalk.com/u/Rod-Knox)\
**Post date:** [July 11, 2008, 3:32pm UTC](https://community.cartalk.com/t/axle-ratio-tire-size-and-final-drive-ratio-s/16542/3 "2008-07-11T15:32:11Z")

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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.

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**Author:** ![CapriRacer](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/capriracer/32/22_2.png) [@CapriRacer](https://community.cartalk.com/u/CapriRacer)\
**Post date:** [July 13, 2008, 9:39am UTC](https://community.cartalk.com/t/axle-ratio-tire-size-and-final-drive-ratio-s/16542/4 "2008-07-13T09:39:26Z")

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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.