General inaccurate speedo punto mk1

[badladjohn]

hi guys,noticed my speedo is way out today whilst checking it with my sat nav.seems its showing 47mph on the sat nav whilst at 40 on the clock, gets worse the faster you go, i have checked my vectra with the sat nav and its showingthe car is travelling slower than the speedo is showing.just wondering if the wheel/tyre combination is throwing things out.its running 14 inch alloys with 60 profile tyres, could this be the cause? its a mk1 90elx cabrio. would like to get this sorted as leeds is the land of the speed camera!. any ideas?

 

[MadMan0]

if you have changed the wheels to a larger or smaller size then this will cause a difference in speedo reading. i thinks it's the bigger the wheel the slower the speedo - so if you fit bigger wheels 40 mph will appear 30 mph on speedo , this will change of course depending on the size.

Also, if the speedo does not move smoothly up the gauge then you might want to oil the conector, im not sure if the puntos the same as the panda but with panda we just undid a few srews then the whole face panel of gauges pops out.

Once out find the wire going to speeddo, clean conectors, and apply a light oil, i.e Wd-40 or this 3 in 1 can stuff

Alternativly you could ask a police man with a speed camera to help with speed checks! im in North East London and find that most will help you out

 

[will4318]

It could be the speedo sensor, on my old mk1 the bottom threaded part that sits in the gear box had snapped off from the sensor so it was spinning on it's own giving the sensor odd readings.

 

[6Speed]

hi guys,noticed my speedo is way out today whilst checking it with my sat nav.seems its showing 47mph on the sat nav whilst at 40 on the clock, gets worse the faster you go, i have checked my vectra with the sat nav and its showingthe car is travelling slower than the speedo is showing.just wondering if the wheel/tyre combination is throwing things out.its running 14 inch alloys with 60 profile tyres, could this be the cause? its a mk1 90elx cabrio. would like to get this sorted as leeds is the land of the speed camera!. any ideas?

I've used a number of different satnavs and all of them show a higher speed than the speedo of the car. Appartently car speedo's are set 3mph below the actual speed anyway(I cant back that up though) and the satnavs ive used are usually about 5mph higher than the clocks (ime). The wheel size does affect the speedo but all you need to do is compare the size of the current wheel to the size of the factory fitted wheel using this website...

http://www.tyresave.co.uk/tyresize.html

and you should be able to work out the speed difference.

 

[m20b25]

It could be the actual needle itself, when it reads 42 on my Seicento its actually doing 28 according to the sat nav and local speed meter signs. Anyone heard of an unmodded 899 on a flat road doing 105mph??!!!

 

[6Speed]

I've used a number of different satnavs and all of them show a higher speed than the speedo of the car. Appartently car speedo's are set 3mph below the actual speed anyway(I cant back that up though) and the satnavs ive used are usually about 5mph higher than the clocks (ime). The wheel size does affect the speedo but all you need to do is compare the size of the current wheel to the size of the factory fitted wheel using this website...

http://www.tyresave.co.uk/tyresize.html

and you should be able to work out the speed difference.

This website is better, does the working out for you.

http://www.miata.net/garage/tirecalc.html

 

[badladjohn]

thanks for your input guys, going to have a play this week and see if i can sort it. will post the results (or my frustrations!)