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zad
13-04-2008, 08:09 PM
just got a v3 tom tom one today and just been out and about in it.

never bothered to plan a journey but have added the speed cameras file thats on here (works well by the way) however i have noticed the speed the sat nav says im traviling is a bit slower than my speedo, normaly about 5mph is this normal or would it indicate my speedo is wrong?
paul01609
13-04-2008, 08:20 PM
most likly your spedo is out,i would say gps would be better at monitering speeds
cosworth4x4
13-04-2008, 08:20 PM
most car speedos over read , id say tomtom is more accurate.
rickt
13-04-2008, 09:49 PM
I just recently read something about this and it read that car speedo's can be out by as much as 10% . Well , I never knew that ! So , it look's like your satnav can be more accurate.
xanadu
14-04-2008, 07:57 AM
GPS will be more accurate than speedo.

If you fit non-standard wheels/tyres to your car, the speed will be even less accurate.
TheBadger
14-04-2008, 07:59 AM
My go 910 shows mine as 4mph less than the speedo and this agrees with one of those checkers that flash up your speed by a school near me.
dave3dg
14-04-2008, 08:32 AM
I agree, believe the satnav as my TomTom 720 reads an accurate 4 mph less than my German engineered Audi. :D

dave3dg
ianskill
27-04-2008, 10:25 PM
hi,i have noticed this on all cars,the vectra (07) astra (54) saxo(01), all these are 4 mph faster than my tomtom. howether,the only accurate speedo to be spot on is my 05 galaxy, german engines/gearbox.
Gr8Guy
08-05-2008, 11:01 AM
My polo is 6mph out when i go over 60! at lower speeds its more accurate.
mf135
08-05-2008, 06:54 PM
my ford ranger is out 5mph the scania truck i sometimes drive is only 2mph that is with tom-tom720
Bazza
09-05-2008, 07:10 AM
My car is 2mph slower than the speedo reads which is a good idea as I set my cruise control at 70mph knowing I'm not going to get caught by any of those pesky cameras ;)
Detlef
09-05-2008, 11:08 AM
Car speedos are allowed ot over-read but not under-read so manufacturers play safe. That is why you get fast lane hoggers blocking at 65mph in the UK.

The difference between new tyres and ones down to 2mm can be 5% and the differences from manufacturer to manufacturer can be another 5%.

Rely on the SatNav.