For those of you with GPS ie road angel etc etc how does your speedo reading compare with the speed shown on the gps

Mine is out by at least 5mph up to 30 and well over 10 mph at say 70/80.

ie speedo reads 80 mph, GPS reads 68 mph

 

Blimey !

I tested mine with a GPS in 2002 and it was 4mph overreading throughout the range...

Mark

 

when the speedo is at 80mph .... my road angel shows 77-78mph. Pretty happy with the accuracy.

 

mine is about 5-6 mph out at 80mph and spot on at 30mph.
Prob adjusting the tyre pressures will account for most of that!

Dan.

 

My road pilot under reads by 3mph at thirty and 5mph at seventy this on a MY98 wagon and my tranny van,read somewhere it was normal for GPS to under read as
speedos in cars are designed to over read by 2-3%.
Perhaps if aftermarket wheels with a different rolling circumference to the originals are fitted then this may throw the accuracy of the speedo out the window too ?

 

might be worth adding ive got an sti5 with 17's on


tyres are 215/40/17

would this make much difference

 

My Snooper S6-R Neo is consistently 10% lower than what my speedo's telling me...

 

Ive got a S6-Neo and it shows around 77mph when doing 80mph on the speedo.

 

Blimey, that's much nearer than mine... 80mph speedo = 72mph Snooper...

I wonder if your speedo is more accurate? Mine's a UK MY00.

 

It'll be the GPS that is right, most car speedos over-read by about 10%. If yours is closer than that it is unusually good.

 

It's not a bad thing really. You never know when that 10% could come in useful...!

 

The 10% figure is about right which is why I'm usually the only one who will pass the copper on the motorway at an indicated 80mph.

 

Having changed all the gear ratios and final drive in my Scoob, with slightly non-standard tyre size on 17in wheels, we did a comparison and the Speedo is now exactly right - 1mph out at 100mph (on a private road of course!).

So it must have been way out before!!

Rannoch

 

My MY01 WRX has had a few different GPS devices in it and they have all read 5mph less than the car speedo whatever speed I'm doing.

 

On a standard WRX Wagon MY95 with standard wheels the speedo was checked using a SPA microprocessor and found to over read 5.5% at 80-100mph.
Changing from standard wheels and tyres will alter the speedo reading and going from 215 50 16 to 215 40 17 actually reduces the speedo error as the rolling circumfrence is slightly less on the larger diameter wheel and tyre set up.
In respect of GPS readouts always remember the indicated speed from the GPS will be something like 3 seconds behind real time.