Incorrect Speedometer Reading

[Hammer]

Originally Posted by SquattingDog

I finally confirmed that my speedo is reading 2-3 MPH faster than it should be, at any speed. 2011 X5d, has factory 20" rims and OEM rubber....

How did you confirm your speedo is out?

Not sure what it's like in North America but in Australia all speedo readings are optimistic (compared to true road speed). This is simply a liability protection by manufacturers to ensure they don't get blamed for anyone caught speeding (or worse, involved in an accident).

But I'm talking small numbers here (2-6 kph difference) ie. true road speed is slower than what's indicated in the speedo (or HUD).

Plus the 20" staggered wheels have a smaller rolling diameter compared to the 18" or 19". The effect of this is to make the speedo read more optimistically that the true road speed.