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Old 11-07-2019, 04:46 PM   #35
davesrave
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Drives: 2014 Boxster S; 2015 Macan S
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Quote:
Originally Posted by Dadhawk View Post
Yea that would have been interesting. Odometers are relatively accurate but not 100%. Used to be that they rolled backwards in reverse which is why you could take a hand drill or other tool and literally turn back time (well miles) on a car (pre-70ish I think is when that stopped).

Current ones are more accurate but could be impacted by a change in tire size, just like a speedometer. They are also impacted by tire wear. As the tire wears, it becomes smaller making the odometer reading higher.

If the odometer is based on a 24.6" tire (that is new calculated circumference of a P215/45R17 tire) for every 1/8" of tire tread wear you gain 25 feet of measured ground per odometer mile. That means for every 211 miles you travel your odometer would be +1 mile off.

Now, I'm not sure if odometers are calculated for medium tire wear so that it balances out over time or not, of if some odometers use a different measurement other than tire rotation and size.
More interesting info, Thanks again. Don't know how they handle tire wear, but my new to me Boxster's computer asks what size tire your running, and weather it's a winter or summer tire.
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