Gps Speedometer

[alter ego]

My gps speedometer was indicating 143MPH but my isf car speed said 150MPH.Obviously this was recorded on a stretch of the Autobahn recently!!

So it looks as though your isf speedos are it liitle bit fast which isn't a bad thing.Having the gps speedo is great because now i can travel a bit faster as its dead accurate.Does anyone else have a gps speedo?I bought mine fromWWW.DIGITAL SPEEDOS.CO.UK as advertised in Classic & Sportscar magazine June 2015 issue.

[steve2006]

I use my sat nav for the speed in those 50 MPH roadworks, nav at 50 shows 52 on car speedo so theory seems to be correct with under reading.

[Corrado]

I think all cars over read for legal reasons, it's a question of how much they over read. The ISF doesn't over state the speed as much as a lot of cars.

[scudney]

Gps speed is always lower than car speed and is the more accurate.will leave it at that for the time being lol

[MrW]

4-5% over reading seems about right. So that same margin at 50mph would have it showing 52 ish. Sounds bang on to me.