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senikc 12-02-2012 09:33 PM

Z3 Speedometer error
I have a 1999 Z3 speedometer is about is about 8 MPH slow, I have checked it with my GPS, also the car has a trip computer which displays the same speed the Garmin GPS does. I feel like the sending unit in the differential should supply the same signal to the trip computer as well as the analog speedometer. I believe the instrument cluster has been changed out at some point in time, prior to my purchase.

any suggestions or thoughts on the error.

Thanks for any information.


Blacklane 12-03-2012 05:21 AM

Look over this thread:

senikc 12-03-2012 06:02 PM

Thanks so much for the information, I did a search prior to posting but did not find the thread. It's a shame BMW did not do a recall to repair this item.

Thanks again

Pinecone 12-04-2012 08:02 AM

Why? It meets their specifications.

BMW specifications are that the speedo read no lower than actual speed and no higher then 10%+2.4 MPH. So at 60 MPH, it is perfectly acceptable for the speedo to read 68.4 MPH.

senikc 12-04-2012 06:09 PM

speedometer error
You have a point, after all why would anyone want to know they are driving 43 mph in a 55?

Pinecone 12-05-2012 07:19 AM

It has to with German TUV requirements that the speedo NEVER read lower than the actual speed.

You can get it closer by changing your tire size. Running 255/40-17 rear tires on our M Roadster and 265/41-18s on the E46 M3 have both speedos almost spot on.

Or one could get a GPS (very useful for other things) and use the speed readout in it.

smayo964 12-05-2012 11:03 AM

Agree with Pinecone on the tire size change. I changed my rears from 50 series to 55's and my speedo is right on the money. The hard part was re-learning not to drive 4-5 miles over what I wanted. LOL

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