Has anyone experinced the difference in speed with the sat nav,ie at 50mph on speedo the sat nav records 47mph The sat nav I have is a 520 Tom Tom.

Yes , just about everyone will see the same effect as the speedo overreads.

Your margin of error sounds about right.

Yep, sounds about right. 70 on the speedo equates to around 67 on the sat nav.

160 on the speedo was around 145 mph on the sat nav (autobahn )

Yes , just about everyone will see the same effect as the speedo overreads.

Your margin of error sounds about right.

Thanks very helpfull glad to know all is OK

Yep, sounds about right. 70 on the speedo equates to around 67 on the sat nav.

160 on the speedo was around 145 mph on the sat nav (autobahn )

Thanks for info but too old to go ont the autobahn to try it out

Thanks very helpfull glad to know all is OK

By law speedos are allowed to overread by up to 10% but not underread at all.

Every car I've been in has been somewhere in the middle

By law speedos are allowed to overread by up to 10% but not underread at all.

Every car I've been in has been somewhere in the middle

What Law is that?

What Law is that?

UK law.

not sure if its the road traffic act or which bit.

actually think it comes from the DOT regulations for construction and use.

What Law is that?

Construction and Use regulations in the UK , though there will be an EU-wide equivalent for other countries