I concur.

 

FWIW - My car was showing 26 today when I was being clocked at 25 by a radar speed limit sign that shows you your current speed.

 

The only car speedometers that are REALLY accurate are the ones in certain police vehicles. They are required to be so that when they pace you, it can be used as evidence.

 

Speedo 67 mph speed limit LED sign 62 mph.

 

I had a chance to take a picture at 200km/h.
The GPS speedo showed 189km/h.
The orange thing in the picture is to hide where I took this picture.

 

Wow, big difference - cool pic though!

 

Are you afraid the Japenese police would track you down using that picture?

 

I am at 77 MPH on digital speedometer at 3000 RPM in 6th gear (as I recall, I think it should be 75 based on calculations). Also with the radar signs that post your speed that have been around town, it seems that I am 2-3 MPH higher that I actually am.

Another way to check speedometer/odometer accuracy is to measure actual mileage over a known distance. My trip computer is about 20 miles more than my odometer at over 8000 miles, (which does not make sense to me).

 

with Garmin GPS it indicates my speedo reads 2mph faster than I'm going

speedo = 80 mph
gps = 78 mph