speedo

[Milby]

i noticed the other day on a nice drive down south my speedo was reading about 80mph and the sat nav was reading about 70mph is there any way to get the speedo calibrated ??

[dom]

What size wheels/tyres are you running? Incorrect tyre size can cause the speedo to read wrong

[thai-wronghorse]

This^^^

Plus the fact your car speedo should read approx 3-5mph above your actual speed which is more likely to be recorded on your sat nav.

[Milby]

185/55/r14

[dom]

185/55/r14

When I had my Mk3, it had 205/50/15s on and the speedo was pretty much bang on.

The difference between 205/50/15 & 185/55/14 is -4.45%

That amount accounts for just over 3mph when doing 70, combined with the speedo over-read you get as standard is about right. If you want to get it to read more accurately then you need larger tyres.

[mrsaunders]

i'd say its probly the sat nav, lets face it there not that accurate are they

[Dogbot]

As said above its the tyres throwing out the speedo, the sat nav  speed is done on gps, although as much as a second time delay it's the most accurate of the two

[mrsaunders]

yeah they are ment to be dead on but its probly just the one i used  i have had experience with a dodgy one

[Gavv8]

The police use evidence based on speedo speed not gps ..nuff said..

[thai-wronghorse]

And coincidentally their sophisticated  radar equipment isn't based around 15 year old analogue VAG clockwork.