Speedo vs GPS

[eldog]

Checked the car speedo tonight

road was busy so had to do it at 90 kph as the fastest speed I could do constantly with the heavy traffic.

car 90
gps average 86 fluctuated 84 to 88 most of the time at 86
calc 86.1

that same difference was noted when I did 100 the other day with the gps

now only to try it on the bike

done. Bike says 94/95, calculation from 5k signs and stopwatch 88
suggest don’t stop on side of motorway at night, truck drivers tend to follow red tail lights. Even though I was well off to one side one truck driver tried to make me into another lane
will try gps next time on bike.

[FJRider]

What I've always wanted to do is to find a friendly policeman at the end of a long straight ...

Anyone tried it?

One found me ... and although he wasn't that friendly ... the number on the ticket matched the max speed on my hand held (jacket pocket actually) GPS.

The GPS was right on the money. And I'd trust it over the speedo anytime ...