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Speedometer off by -1 MPH

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Curious if anyone else has noticed the speedometer being off by -1 MPH, e.g. car says 60MPH but in reality is going 59MPH. I can verify this with both GPS and those radar speed limit sign things.

6046_61MPH_CLSTuPg.JPG
 
Mine is exactly on, when it is stopped!

On my 2007 Lexus LS460L the car reads about 3 mph fast for speeds above about 20 mph. In the Lexus group there was talk about challenging Lexus about their warranty, since it is both time and mileage based and the odometer shortchanges the warranty on mileage. No issue with unlimited Tesla mileage.
 
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Well - according to German law the speedometer can only have a tolerance to the high side. It can never show a speed lower than the one you are driving.

The formula is

actual speed < speed shown by speedometer < actual speed + 10 % plus 4 km/h

Source:
§ 57 Par. 2 StVO
Anlage zu § 57 Par. 2 StVO

I assume there are similar laws in other countries.

The MS has the most accurate speedometer of any car I have so far driven - I love it. Until I knew this, I had to pay one (small) speeding ticket. But now I know!
 
I've noticed a small discrepancy, but never really tested it to get an accurate number.

All of our previous cars (German) were off as well, and it scaled as you went faster). There was "talk" on some old forums about German automakers doing this because they didn't want to be held liable if a ticket was issued saying they were going faster than the speedo indicated.

Don't know how true that is, but almost immediately I noticed the Model S always seemed to indicate a speed closer to real speed than past cars.

*edit* and it seems Johann ninja'd me and confirmed the chatter.
 
Well - according to German law the speedometer can only have a tolerance to the high side. It can never show a speed lower than the one you are driving.

The formula is

actual speed < speed shown by speedometer < actual speed + 10 % plus 4 km/h

Source:
§ 57 Par. 2 StVO
Anlage zu § 57 Par. 2 StVO

I assume there are similar laws in other countries.

US law is similar.

PS The Prius is a big fat liar on speed and fuel economy.
 
Not a scientific measurement, however I have driven by many portable radar speed display trailers and my car's speed always shows at least one mile higher on the display than what the speed sign shows.

My other cars also show I am traveling faster than what the radar displays show, so it's not just Tesla that does this. Personally, probably a good thing due to the ease at which the S gets up to speed (and beyond).
 
I just want to add; The Tesla has the most accurate speedometer of any car I've ever driven. I am just curious if anyone else noticed the speeds consistently off by 1MPH. I'm trying to determine if it's a margin-of-error thing, or if it's purposely wrong by Tesla.

//On a side note, I have a BMW K1200S motorcycle which has always been dead accurate.
 
The roadside radar almost always shows +1 mph, the few times when it doesn't show +1 it's zero.

This is my experience as well. I was just watching this during a long road trip. Given the Elon design ethic, I would imagine that they calibrate the speedometer to be 0.5 mph high, just to be legal, but to be otherwise as accurate as possible!

I really appreciate being able to rely on the speedometer as accurate, as well as the incredible stability of the cruise control!
 
Speedometers on all cars read high from the factory. Modern cars less so than older ones as accuracy of the components is easier to guarantee now, but always high. It gives the manufacturer some wiggle room so as not to break the law stating they can't read low. (It also saves them from owner lawsuits when someone gets a speeding ticket!)