Mole wrote:
Speedos in modern mass-produced "type" approved cars are allowed to over read by 10% plus 2.5MPH. As has been said, they are not allowed to UNDER rear AT ALL. There's an EC Directive about it, 75/443/EC. The ship's depth sounder or aircraft altimeter analogy would therefore be that ships could only have depth sounders that recorded the water as being a bit shallower than it really was and planes could only have altimeters that recorded the ground as being a bit nearer than it really was. Under our Construction and Use Regulations, it is an offence to drive a car with a defective speedo. If you try to claim you were speeding because your speedo was defective, you just add a second offence to your speeding offence!
Heavy goods vehicles can get their tachographs re-calibrated but there's no mechanism for doing so on a modern car speedo. Quite often, the error the speedo records is non-linear anyway, depending on the speed travelled at. Also, the speedo's accuracy will vary with tyre size, pressure and level of wear.
I have a 1997 ford galaxy which i have just changed the clocks on due to the old ones being damaged the problem is the speedo i just fitted reads 45mph when i am doing 30mph & the faster i go the more inaccurate the speedo is, i have been told by my local ford garage that they can recalibrate the speedo so it is accurate but it will cost me £94, so i would assume that other manufacturers are able to do the same, even if the price is a rip off.