Misread the slow reading in the original post. My speedometer reads 60 mph and the gps shows 65 mph, for example, so I am always travelling more quickly than the speedometer is indicating. I would be happy with 10% over but 10 % under puts me at risk of a speeding fine even when I am trying to behave.
Same point though in that if I find out how to adjust the speedometer I will share the outcome.
My understanding is that it is illegal to have a speedometer that under reads, whereas over reading isn't a problem. Something needs to be done!
