Thread: Odometer inaccuracy

Based on GPS speeds mine is about the same as yours. Even my 2 Mini's are about the same.

Hi Jesse B

The odometer (speedo) is designed that way out of the factory, I had this confirmed by the dealer. The decision process is; to have an accurate speedo reading taking into account wear on the types (which can be up to 20mm off the circumference from new to warn) and to not get sued by drivers for having an speedo that posts a speed over the rated limit, the manufacturers will up the speedo reading 2-5% above the "actual" road speed you are traveling. Its better to post faster speedo speed than the actual road speed.

This can be confirmed with a GPS which will show a far more accurate road speed than the Speedo. In fact, I jumped into my onboard GPS's diagnostics (press the top of the middle of the screen for 5 seconds and enter 753 as the code if you have one) and it shows the accurate GPS road speed.

At speedo speed 50kph I was traveling 48kph, 80 was 77 and 100 was closer to 96. This explains why cursing at 119 on the Highway the radar guys wave at me, I was really only doing about 114km!

This will of course have an affect on the odometer and mileage calculations, you will have actually traveled less than your odometer has reported.

Col.

Originally Posted by Colin Pedersen

Hi Jesse B

The odometer (speedo) is designed that way out of the factory, I had this confirmed by the dealer. The decision process is; to have an accurate speedo reading taking into account wear on the types (which can be up to 20mm off the circumference from new to warn) and to not get sued by drivers for having an speedo that posts a speed over the rated limit, the manufacturers will up the speedo reading 2-5% above the "actual" road speed you are traveling. Its better to post faster speedo speed than the actual road speed.

This can be confirmed with a GPS which will show a far more accurate road speed than the Speedo. In fact, I jumped into my onboard GPS's diagnostics (press the top of the middle of the screen for 5 seconds and enter 753 as the code if you have one) and it shows the accurate GPS road speed.

At speedo speed 50kph I was traveling 48kph, 80 was 77 and 100 was closer to 96. This explains why cursing at 119 on the Highway the radar guys wave at me, I was really only doing about 114km!

This will of course have an affect on the odometer and mileage calculations, you will have actually traveled less than your odometer has reported.

Col.

Lucky you're not in Victoria! You'd be pinged anyway, anything more than 3km over and you're done.

Originally Posted by Colin Pedersen

Hi Jesse B

This can be confirmed with a GPS which will show a far more accurate road speed than the Speedo. Col.

Just make sure your are on a flat road with the GPS or readings will be incorrect
Cheers Ken

Originally Posted by Colin Pedersen

This will of course have an affect on the odometer and mileage calculations, you will have actually traveled less than your odometer has reported.

Col.

Thanks Col - but this is not actually the case with my D4. Like yours, mine shows a higher than real speed on the speedo, which I am not fussed about. But instead of having traveled less km than my odo has reported I have actually done more!

I checked this by setting a trip meter to zero alongside a roadside marker plate saying "Perth 160 km". I also made a note of what was showing on the overall km count. Then when I reached the "Perth 60 km" plate I checked both - they were registering 96.7 km traveled, but I'd actually done 100 km. So, while the speedo is high the odo is low - hence my original statement that instead of having done 35000 km from new I now find I've done 36125 km - a fairly significant difference.

Just to be sure that it was not this particular set of roadside plates that were wrong I checked against two further sets, one being a distance of 80 km and the other 90 km - exactly the same percentage under-read!

Those signs aren't always spaced correctly.
Often they are out 5-7kms

Don't complain, reading lower is better for your resale!!!

Hi Jesse,

If you have a separate GPS unit, measure against that on a long straight level road. Or calc a travel distance using Google Maps and drive it.

Cheers,

Gordon

Originally Posted by gghaggis

Hi Jesse,

Or calc a travel distance using Google Maps and drive it.

Really? I've always found Google Maps to be pretty inaccurate themselves. Not just on actual road routes but on distances as well. whereis.com seems a bit better but they also seem not to be able to keep up with infrastructure changes making the actual distance different from that indicated on the website.

From what I can tell all new cars over the last 5 years come from the factory with low reading speedo's. I read "Wheels" regularly and they use "Actual speed at 100km/hr..." as a test point and nearly all of them are actually 96 or 97km/hr