.... in comparison to the actual car speedo... i was driving today and car was saying 80MPH and TomTom was reading 72MPH

being gps, I would say the TomTom is no more than 1% out, and that is only down to poor refresh rates.

 

The speedo can be well out, but the average is 10%. This can be much more if you change your wheels for bigger/smaller ones.

I found my speedo was out about the same compared to the GPS and the AVCR-r

I have always found if you go 2 sizes up in wheels you will be 99% right with the tom tom :)

GPS is about as accurate as you get.

The speedo isn't.

thx everyone :D

The speedo on my zed is only out about 2 mph all the way up compared to my road angel :) on the bimmer its about 5 mph - doesnt seems to be % it looks constant throughout the range.

I always go by the tom tom makes the average speed camera roadworks pass at 55 on speedo lol, different in all cars. Van @ 100mph on speedo is about 93 on sat nav, my M3 is about bang on, 80 on clock is 79 on TomTom, my zed was about 4mph out at 80 (76 on satnav)

My clocks read about 5% under!

 

But the speed sensor on the gearbox to cock on to gps at a constant 70mph

My mates 2006 C2 was 11mph out at 75mph!! I was shocked!!! The Zed is about 4mph out 75!

My ZX is about 3mph out compared to the sat nav from around 70mph; it's almost bang on up to about 50 though.....

 

The SLK is seldom more than 1mph out at any speed but the Rav-4 is almost 10mph out at 90:smash:

 

Richard;)

my zed speedo always reads correct and the same as the gps... 0mph

 

i havent driven it for fookin ages :(

The speedo on my zed is only out about 2 mph all the way up compared to my road angel :) on the bimmer its about 5 mph - doesnt seems to be % it looks constant throughout the range.

 

So when your speedo reads 0mph, you're actually going backwards 2 mph;)

theres always 1

I was sitting at a steady 70 on the expressway today and my TomTom said 63mph, that was in my BMW.

If you are moving at a steady rate for more than about 5 seconds and the GPS can see plenty of satellites then it's reading will be pretty damn accurate. At 70 mph my BMW over reads by approx 1 mph, whereas the Z over reads by 6 mph.

My cars speedo is now no more than 1-2 mph out compared to tomtom (I have calibrated it to match), I also have a HUD which is no more than 1mph out as well, so lots of speedos (You can never have too many with so many speed cameras around)