speedo reading 5mph out, according to satnav?

[Whalli17]

In my 01 1.2 16v dynamique, noticed the speedos out 5mph or so when im using the satnav. is this normal? as on my previous car it was the same except when i swapped the 13 inch wheels to 15 inch this sorted it.
any advice?

 

[jamesp24]

All speedos are set out.

 

[phoenix1]

sat nav speed is based on straight line ,level and flat , your speedo measures over any terrain. think of a triangle over the top is a longer distance than across the bottom

 

[Whalli17]

Ahhh i see... my bad haha
cheers guys!

 

[plasticmorph]

speedo will only ever be accurate up to about thirty. I would say that having worked through four cars in 18 months, but with the same satnav, clio's are especially bad!!