so i have come to figure out that my speedometer is displaying the wrong speed. i first noticed this with my obd2 reader displaying about 4/5 mph slower than the speedometer. then to test which was wrong i went through one of those police radars and it was displaying the same speed as my obd2.

does anyone know why this could be happening? thank you!

 

Bmw usually sets the speedos higher than actual speed, mines 2 mph hour.

 

According to my GPS, my speedometer reads 2 mph high at urban speeds, and 3 mph high at highway speeds. It's "normal."

 

The search engine found this for me. Hope it helps.
https://www.northamericanmotoring.co...archid=9885097

 

The speedo on our JCW reads between 3 and 4 mph faster than we're actually traveling on the highway.

 

Add tire and rim varrations to the mix....makes it even more off....
Think about it this way....
The speedo is set read normal or even slightly faster than actual (for legal reasons) with the wordt case factory tire/rim combo....if you calculate the revolutions per mile of the different OEM sizes, there is quite a bit of varration......

Once upon a time....some carmakers sold cars with Speedo's that you could input the revolutions per mile from the tire maker and have a accurate speedo....but some folks did not understand...and made the speedo read anything they wanted...made a legal issue...some place REQUIRE a car sold to have the speedo read HIGHER than actual....so BMW/mini does just that...
PS....
I would trust a GPS BEFORE I TRUST A RADAR SIGN.......