Well tried out a GPS Navman pocket pc version in the car today , and it would appear that if we assume the GPS to be accurate , my Octy is showing 5 mph faster on the speedo . Is this normal that they are so inaccurate . :confused:

Sounds about right. Depends on the rolling radius of the wheels, but on mine if the clock shows 80mph, the GPS shows 73mph. I tend to hang at just under 80 on the clock to keep things kosher.

My rallied-up Scirocco showed 115 on the clock when the GPS showed only 100mph.

My Golf is only ever 2-3mph out.

Have you changed your wheels and fitted tyres with a different profile?

My Octavia is also 5mph out at 80mph, the Fabia is a bit less around 3mph out at 80mph.

There can be as much as 3-5mph difference between new properly inflated tyres and worn out, under inflated tyres.

Cheers

Lee

Hi,

My Octy TDI compares as follows to my GPS:-

GPS Octy

30mph 33mph

40mph 44mph

50mph 55mph

60mph 65mph

70mph 75mph

I have compared the GPS against a calibrated speedo and it is either spot on or 1mph under.

Regards

I am going to set the speed warning on the GPS for 75 mph , which will be 80 on the speedo . So i have not been driving as fast for these last 6 months and slowing down at cameras when i was not even over the speed anyway . P

My Fabia vRS is about 7% fast whatever the speed. Well, beyond a certain point obviously I wouldn't know ;-)

From 30 - 60, my speedo is 2 mph out

@ 70 it is 3mph out

@ 80 it is 3 mph out

@ 90 it is 4 mph out

you can guess the rest

Hi' date='

My Octy TDI compares as follows to my GPS:-

GPS Octy

30mph 33mph

40mph 44mph

50mph 55mph

60mph 65mph

70mph 75mph

I have compared the GPS against a calibrated speedo and it is either spot on or 1mph under.

Regards[/quote']

My A6 TDI (110) is exactly the same. GPS is original Road Angel.

My speedo is 4mph faster than Tom Tom Go says

So it would seem , that to know true speed one needs GPS , .Now all i have to do is test out the GATSO POI i have loaded , they all show up on the maps and i am getting the warning ping but so far they have all been on too far away , may need to reset the distance check . What would be the best recomendations for setting this distance .