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Speedometer mph vs gps mph

DaveORD

Member
Mar 12, 2020
629
550
Chicagoland
All depends on your make and model of GPS unit... ;)

But referring to MY, then no. Are you using OEM tires or did you install something else? Diameter is supposed to 28.0 for MY, that is what the speedo is expecting. If your tires are a slightly bigger diameter, either because you are using something different, or because they are over inflated, then that could cause it. Also, how do you know that your GPS measurement is accurate? Just because it is GPS does not mean precise. Number of satellites in view, the accuracy error, etc. all factor in. GPS could vary depending on bunch of factors.
 
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73Bruin

Member
Nov 7, 2020
91
30
Torrance, CA
My MY is showing about 2 mph faster than actual GPS mph with highway speed.
Will this be fixable with software updates?
I would assume that almost anything on the MY could be addressed by software updates. However, I would be very surprised if Tesla would ever base the speedometer on the GPS on a real time basis, or even use it to correct its errors periodically. From what I have read in the past, speedometers are more a quide than an absolute reference and for reasons tied to commercial vehicle rules read higher than the actual speed just like you are experiencing. There is a great Quora write up about this.

Is it true that car speedometers are slightly inaccurate to reduce speeding? - Quora
 

laceyboy

Member
Aug 9, 2020
133
87
Lacey WA
All depends on your make and model of GPS unit... ;)

But referring to MY, then no. Are you using OEM tires or did you install something else? Diameter is supposed to 28.0 for MY, that is what the speedo is expecting. If your tires are a slightly bigger diameter, either because you are using something different, or because they are over inflated, then that could cause it. Also, how do you know that your GPS measurement is accurate? Just because it is GPS does not mean precise. Number of satellites in view, the accuracy error, etc. all factor in. GPS could vary depending on bunch of factors.
I forgot to provide a bit more info.
My MY came with OEM parts, no aftermarket.
GPS I'm talking about here is my Galaxy S21 Ultra and using Google maps for navigation.
Mph reported on my phone matches with my previous vehicles I owned.
I will check with my MX later.
 

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