All factory speedometers read between 5-10% faster than your actual speed.
This is specifically to prevent people from overspeeding, and to prevent lawsuits from people getting speeding tickets who will try to put the blame on a defective speedometer.
Very few cars have a speedometer that is properly calibrated. They used to do it for police cars in the US. Not sure if they still do.
The only time a speedometer will read too slow is if you have much bigger tires on than the factory tires.
I use Ulysses. Terrific interface, great display... easy to set up.
Do note that Android apps are limited by your phone's on-board GPS, which only updates once a second... but that's enough if you only want to know your average speed.







Reply With Quote
