A friend of mine recently traded his 5 series for a Toyota Highlander. He drives down to Florida every winter and remarked that on his BMW it was always showed about the same mileage every year. But in the 1st trip in the Highlander, the trip odometer showed a lot less mileage that the BMW.
Got me to wondering a couple of things.
First, how accurate are the odo/speedo gauges in any car? Are there regulated tolerances that must be met to certify the car?
Second, how much does tire wear affect the displayed speed and mileage? Obviously, as the tire wears it becomes smaller and it takes more revolutions of the wheel to go the same distance. But how much is this difference and could it lead to a material discrepancy?
Third, which was likley "more right" the BMW or the Highlander? Has anyone tested to see how accurate their speedometer or odometer actually is? How did you do it?
Any other thoughts?
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| Reply » Accuracy of odometer/speedometer |
All BMWs have optimistic speedometers by a fraction (around +5% or so). However, the odometer I'm pretty sure is accurate.
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| Reply » Accuracy of odometer/speedometer |
Odometer is normally just about spot on. The allowable speedo error is 10% + 2.4 MPH. In 3 BMWs, one is spot on, the other two are a bit off.
As the tires wear they odo will start to read high for the same real distance, the speedo will also read higher.
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| Reply » Accuracy of odometer/speedometer |
I compared my speedo on my E90 with the reading from a handheld GPS. The difference was 2-3mph faster for the speedo on the car. With other cars I have tested this the speedo and GPS were almost the same. Accuracy does depend on tire size. I once switched wheels going to a slightly larger size and the odometer started to show a noticeable difference on longer trips where I knew the distance prior to the wheel switch.
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Accuracy of odometer/speedometer