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I was curious about how the odometer reads mileage with bigger tires, so I tested my odo on a stretch of highway where they have an odo test. After the 4 mile mark, my odo read 3.5 miles. It seems like the odo reading should not be affected by tire size, but how would you explain my test result? Not that it is a bad thing...


Edit: I went from stock tires to 285/75/16.
 

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::TACOBOY:: said:
I was curious about how the odometer reads mileage with bigger tires, so I tested my odo on a stretch of highway where they have an odo test. After the 4 mile mark, my odo read 3.5 miles. It seems like the odo reading should not be affected by tire size, but how would you explain my test result? Not that it is a bad thing...


Edit: I went from stock tires to 285/75/16.
if your speedometer is off, then basicly your odometer is off the same percentage as your speedometer since they work together and both receive the same signal. but i wouldnt be complaining too much since your odo. is not counting as fast your mileage wont rack up as fast... :D but check the speedometer with actual speed by either gps or the signs that tell ya how fast u are going. u are probly actually going a lil faster than what it shows. and i know u dont want a ticket...
 

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Your odometer calculates mileage based on the number of rotations in the tranny. It must therefore be calibrated to the size of tire it came with from the factory. Going to a bigger tire will reduce the number of rotations necessary to achieve the same linear distance, so the ODO only thinks it went 3.5 miles.
 

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::TACOBOY:: said:
I was curious about how the odometer reads mileage with bigger tires, so I tested my odo on a stretch of highway where they have an odo test. After the 4 mile mark, my odo read 3.5 miles. It seems like the odo reading should not be affected by tire size, but how would you explain my test result? Not that it is a bad thing...


Edit: I went from stock tires to 285/75/16.
And don't forget when you are crying about your lost gas mileage with the bigger tires and the odometer says only 210 miles on that tank of gas that you actually went 240 miles. And when the speedometer says 35 you are going 40.
 

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well i can tell you what ive got goin on. 35s and 4.88 with auto. speedo reads 85 im goin about 73 or so. yet the odo is off by .1 of a mile. and when i put the dakota digital box in and then the speedo was dead but the odo read really low. i was gettin like 100 miled per tank according to it which i know it wrong. here is somethin else . when hooked up to the scan tool, the speed is dead on the scan tool and off on teh speedo. im very confused.

Justin
 

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I've run a few different tire sizes on a couple different rigs with 4.10 and 4.56 gears....

I've found a rule of thumb that works for me (at least on the stock 4.10 gears), is:
Every 2" increase in tire size makes about a 7% error in speedo/odo.

Best way to check it is to hit the interstate, and use the green mile marker signs with the odo....

Set one of your trip odo's to "0.0", when you are even with a mile marker sign....I usually go at least 10 miles, and usually like to go 20 or 25....Then compare that to your odo reading....

A GPS works well too....
I think my 99 origianlly came with the 265's, but when I bought it, it had 31" SSRs on it, and my odo reads just about perfect +/- 2 MPH compared with my GPS... :)
 
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