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Discussion Starter · #1 ·
Alright. Having my speedo off is finally pissing off enough to get it changed. Is there a chart or calculator to find what speedo gear I need for my gear and tire combo? I've searched and come up with nothing. My local dealer wasn't worth a pinch of $hit either.
Thanks for the help. Ryan
 

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Each tooth change is approx. 3 mph
 

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Yep, 1 gear tooth = 3mph change, running at 60 mph.
 

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Got this off a Jeep site, but the caculation is the same..

oldgear is the # of teeth on your current speedometer gear
newgear is the # of teeth of the replacement gear you need to recalibrate your speedometer.

Simple Speedometer Recalibrations
Jeepers are perpetually modifying their vehicles. Sometimes, these modifications make speedometer recalibration necessary. Any change in the ring and pinion or tire size can throw off the speedometer. The simple way to calculate the proper speedometer driven gear is by setting up a ratio. The ratio should look like this:


newGear * newTire = oldGear * oldTire

or

newGear/newRingAndPinion = oldGear/oldRingAndPinion


Solve this ratio for newGear to determine the proper tooth count for the speedometer gear. For example, if you had 225/75R15 tires (approximately 28.2" in diameter) and you swap in 33s, you would set up the following ratio:

newGear * 33 = 27 * 28.2

newGear = (27*28.2) / 33

newGear = 23.07 (23 tooth gear)

Tom
 

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Discussion Starter · #6 ·
Thank you!!!! Now ill finally get to see my real mileage numbers! The 14 just wasn't cutting it anymore
 
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