[GregW / Oregon]

Where is the speedometer driven from? As delivered my car consistently read ~2 mph fast, judging by various radar speed signs at several different speeds. Since upsizing the rear tires to 305/30R20 it is now about 1 mph. Not a big deal, just curious. I had read a long time ago that Germany allows leeway for the speedometer to read fast, but none to slow.

[KC87ZB]

Almost every manufacturer sets the error on the speedo high. I find my M2 to be 1-2 mph off at 70, which actually isn't too bad. My motorcycle is off 4 at that speed (only going 66). GPS confirmed on both.

I don't know if BMW has a dedicated speed pickup or uses the wheel speed sensors.

Every forum has posts about this and then the possibility the odometer is off.

[ednir98]

Every BMW has +2mph programmed into the speedo, even more noticeable in cruise (set cruise to 80 it will go 78). It can be coded out pretty easilly but it’s probably still not worth it.

[Laguna Seca Blue]

Completely normal. Every BMW I’ve owned has read about 3mph or 5km/h high. BMW calibrates its speedometer for stock tire circumference.

I like thinking I’m going faster than I am — sure it’s saved me a few tickets

[RockCrusher]

Since circa 2002 various cars -- German cars -- have had an optimistic speed reading from a worst case of 5mph to 2mph. All cars fitted with factory sanctioned wheels/tires, in some cases larger than the base wheel/tire size.

But in viewing the vehicle speed via an OBD2 scan tool the reading is accurate, that is it agrees with GPS speed and the occasional side of the road speed sign which relies on radar.

With the first car that I noticed this speedo optimism I checked the odometer over 200 miles of pretty straight/flat driving (across northern KS) and the error was 0.2 of a mile over 200 miles. Can't remember now if the error was in my favor or not.

At any rate I was comfortable the speedo error was not affecting the odometer and thus I was going to get a full 50K miles of warranty.

[JABCAT]

Originally Posted by ednir98

Every BMW has +2mph programmed into the speedo, even more noticeable in cruise (set cruise to 80 it will go 78). It can be coded out pretty easilly but it’s probably still not worth it.

Apparently this. It's annoying if you have other vehicles besides BMWs. Always have to remember that the display is +2-3 mph.

[Carefree]

All 3 of my BMW vehicles display 2-3mph higher than radar and laser devices.

[techwhiz1]

Every BMW I've owned in the last 30 years has read high.

BMW would rather be optimistic than you get a ticket because it was reading low.

[DomMuc]

add other wheels/tires with with more rolling circumference-- speedometer will be more exact...
because of that it has to show more with oem spec
( in europe it has to show 1-2% more by law)

[Tag]

Nothing new. On the flip side they also always underrate their cars power output figures.

[Squidget]

And not just BMWs. I've also driven Toyotas and Fords that read high. I assumed this was a just a common practice, TBH.

[blue135]

And Lexus and Chevrolet - in my experience

[aerobod]

Porsche and VW, too.