Hi every body,
I was on the autobahn last night and was at a controlled speed of 135km/h so just cruising.
I checked my gps and the speed was 125km/h at this moment.

10km/h difference at this speed is ok you think?
I just try at (much) higher speed later and the difference is almost 15/20km/h between tachymeter and gps...

What do you think?