Speed shown on display - accuracy?

[qldoldun]

I am interested to find out how accurate is the speed displayed on the screen? My previous vehicle (Forester) always indicated about 4% more than the actual speed (GPS).
Also, how does the MY actually read the speed? Sensors?GPS?
Any help appreciated.

 

[Mike_TV]

Today, I suspect it's GPS as my casual comparison to using navigation apps on my iPhone have the same speed exactly as what the car reports.

A future update will add dead reckoning which would use wheel sensors, compass heading but not GPS.

 

[GtiMart]

Since you could lose gps signal at any time, I don't believe it's gps based. I believe all cars rely on the number of rotations per minute of the wheels. It just happens that Tesla have made the speedometer pretty precise whereas many manufacturers make them more optimistic (read over).

EDIT: An Audi I had many years ago had the speedometer a few km/h higher but if you displayed the speed in a numerical data field, that speed was precise. It was by design.

 

[mongo]

I am interested to find out how accurate is the speed displayed on the screen? My previous vehicle (Forester) always indicated about 4% more than the actual speed (GPS).
Also, how does the MY actually read the speed? Sensors?GPS?
Any help appreciated.

Speed is from wheel speed sensors (same ones used for ABS/traction control).
Per federal regulation, it can read faster than actual, but cannot read slower.
Changing tire circumference will impact accuracy, Tesla has a config menu for the standard sizes.

 

[CarterStC]

My 2018 Model 3 is usually showing 2 mph faster than I'm actually driving. I haven't checked my week-old Model Y yet.

 

[Fourdoor]

My 2018 Model 3 is usually showing 2 mph faster than I'm actually driving. I haven't checked my week-old Model Y yet.

My 2021 MYP has the same 2 mph differential.

Keith

 

[JKad]

I checked with my GPS, and the vehicle was reporting exactly the same speed. I’ve had a cop check my GPS speed and it is spot on.

 

[MrOlatheGuy]

My experience over the years, all of my cars read about 2mph over. Given that consistency, I'm left wondering if that's the standard for all car manufacturers.

 

[Fourdoor]

My experience over the years, all of my cars read about 2mph over. Given that consistency, I'm left wondering if that's the standard for all car manufacturers.

My experience is that my Chevy Bolt is dead nuts on with the GPS speed and my MYP speedometer reads 2 mph faster than GPS speed, so it is not all manufacturers.

Keith

 

[TomServo]

I used my GPS DRAGY to measure speedometer accuracy BEFORE and AFTER I swapped the OEM 21” tires/wheels with some 18s. At various speeds up to 75 the car displayed 2 mph lower than the DRAGY.

After I swapped the 21s for the 18s with 245/50 tires and the error was the same, with the car displaying 2 mph less than a GPS accurate reading, 65 indicated is actually 63 mph. Oh and TSportLine told me to leave the Wheel Setting at 21”. There is a .4” difference in diameter between the tires but I guess not enough to trigger a delta.

That’s good info to know when changing tires/wheels.

 

[bob00]

My MY is good, pretty much dead on compared to numerous radar readers. My Merc was consistently 3kmph off (slower than actual) - 19" wheels

 

[DerbyCityY]

My experience with tires comes more form trucks. Clearance and all that. You can take one manufactures similar sizes and get different diameters with corresponding different circumferences. I'd be curious to see if our tires are uniform in build.

 

[CarterStC]

I'd like them to allow us to calibrate it to exactly the traveling speed.