Inaccurate Speedometer

[ranss12]

The speedo on my Model 3 reads about 1.5 - 1.7 mph high. Every time I pass one of those automatic radar speed indicators along the side of the road it shows either 1 or 2 miles per hour lower than indicated in my car. Is there a way for an owner to adjust this so it reads accurately or does the SC need to do it? I'm using the stock 18" wheels. What I wonder is if this affects the odometer, Wh/m readings, and/or other calculations.

 

[jelloslug]

I doubt it's the car that is incorrect.

 

[ewoodrick]

I doubt that car sign is correct, I doubt if the car is correct. As far as I know, there is no way to change this, as it becomes a legal issue.
I GPS is probably the most correct.

I believe that cars are allowed to be off by 5-10% in gauge readings and be legal, hence one of the reasons why law enforcement has to give some leeway in tickets

My previous Leaf was off by 2-3 mph, most cars are.

 

[Lloyd]

BMW does this also.... When I complained that it was inaccurate the response that I got was that "in US markets it was designed this way for safety and avoidance of litigation"

I argued that 'how is being inaccurate safe?'

Anyway, Tesla is not the only one.

 

[zosoisnotaword]

Your speedometer is correct. The radar speed indicators are always going to be slightly lower than actual speed due to the cosine effect.

 

[Kermee]

According to a high-resolution GPS receiver, least at speeds between 60-80 MPH, my speedometer registers a difference of <1 MPH.

 

[tivoboy]

I doubt that car sign is correct, I doubt if the car is correct. As far as I know, there is no way to change this, as it becomes a legal issue.
I GPS is probably the most correct.

I believe that cars are allowed to be off by 5-10% in gauge readings and be legal, hence one of the reasons why law enforcement has to give some leeway in tickets

My previous Leaf was off by 2-3 mph, most cars are.

I think technically the number is 4%, but it varies with speed. I haven't had a single car that was exact (measured only with a GPS vehicle speed testing device. changes in tire pressure, wheel size, profile, it's all going to affect the speedometer as it was set from the factory.

It's also traditionally not really user/owner adjustable unless it's really an issue.

 

[kmcdds]

I had Waze on while driving yesterday and Waze had me consistently 2-3 km/hr slower than my speedometer. I wasn't sure which one was accurate.

 

[Stu Redman]

I timed and tracked both speed and odometer on a 15 mi. stretch of mile posted highway. Both were 1% high at 60MPH. 19 in. wheels. Not too bad really.

 

[Reid]

BMW does this also.... When I complained that it was inaccurate the response that I got was that "in US markets it was designed this way for safety and avoidance of litigation"

I've actually heard that German cars read high because of GERMAN laws, where there's some legal liability if the speedometer ever were to read low (eg, if you put on the wrong size tires, it still has to not read low). Really vague and silly explanation, but I've heard it as long ago as 15+ years, and the German cars do tend to be off by more.

Motorcycles are REALLY bad, though (and here I'm thinking of Japanese motorcycles, not sure how others compare).