Tire/Wheel Size and Odometer Impacts (1 Viewer)

TheGrrrrr

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Ok, just trying to make sure I'm thinking about this correctly. If the speedometer is inaccurate after putting larger than stock tires, then wouldn't the odometer be off by the same amount? For instance if the stock 285/60/18 wheel/tire setup were replaced with say 305/75/17 wheels/tire setup, then it looks like the circumference increases by 11.1%, which causes the speedometer to show a speed that is 11.1% lower than actual. Wouldn't this also mean that a vehicle with an odometer that reads 200,000 miles, which had the stock wheels/tires replaced with 35's at 100,000 miles actually have 211,100 miles on the vehicle? With more unsprung weight and rolling resistance than stock wouldn't those 111,100 actual miles on the 35's be more work/per mile on average than the first 100,000 assuming similar usage?

Does this matter? Would this cause you to look at a higher mileage vehicle that has been modded differently? Do I even have my math/thinking correct? Mostly just curious as I hadn't really thought about this before.


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radman

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You are correct. Someone on here recently admitted to going big in order to cheat the odometer 😂 (not me!)
 
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Note that the spedometer is deliberately incorrect with stock tires - it reads a few mph fast at highway speeds. So you won’t be off as much as a chart would indicate. However, the odometer is more accurate with stock tires than the speedometer is. There is at least one thread on here covering this, do a search if interested. Something about liability to automakers in Japan if a speedo ever reads low. So the speedo deliberately reads faster than you’re going. That is the case with my 2016 with stock tires, versus gps readings and versus highway “you’re driving too fast” radar signs.
 

TheGrrrrr

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Note that the spedometer is deliberately incorrect with stock tires - it reads a few mph fast at highway speeds. So you won’t be off as much as a chart would indicate. However, the odometer is more accurate with stock tires than the speedometer is. There is at least one thread on here covering this, do a search if interested. Something about liability to automakers in Japan if a speedo ever reads low. So the speedo deliberately reads faster than you’re going. That is the case with my 2016 with stock tires, versus gps readings and versus highway “you’re driving too fast” radar signs.


I had noticed this with the speedo, but wasn't sure if it was a calibration problem or intentional from the factory. With many Jeep sold new with aftermarket tire/wheel packages, I would think that odometer accuracy would be a common topic of discussion, but have never really heard it come up before.
 

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