Don't assume your speedo is out by as much as that. Some car speedos are actually quite accurate as long as you are driving on the tyres it is specced for. The legislation is that they are not allowed to understate the speed, and are allowed to overstate the speed by up to 10%.All car speedos ar calibrated to read high ie. It will read 60 when actual speed is 55 km.
Also the speedo reading acuracy can change depending upon the wear on the tyres
The calibration isDon't assume your speedo is out by as much as that. Some car speedos are actually quite accurate as long as you are driving on the tyres it is specced for. The legislation is that they are not allowed to understate the speed, and are allowed to overstate the speed by up to 10%.
The calibration of a car speedos is unilateral, meaning that instead of a plus or minus reading it plus or zero reading so it will always read faster than you are travelling but never slower, this takes into account of all uncertainties so you cannot blame the makers if you get done for speeding. Generally you will find at 60 mph your speedo will be reading 65Don't assume your speedo is out by as much as that. Some car speedos are actually quite accurate as long as you are driving on the tyres it is specced for. The legislation is that they are not allowed to understate the speed, and are allowed to overstate the speed by up to 10%.