Quote Originally Posted by xsnaggle View Post
An easy way to check the error on your speedo is put in a route to google maps and set your cruise control. Then compare the speed on the satnav to your speedo reading. (you may have to go on a 40 or 50 MPH road and set the speedo at 43/54 )
A sat nav is a guidance tool and has no legal binding, the speed shown on your “speedo” is calibrated for both mph & kmh and subject to legal, product and functional regulation & safety.