European law (
ECE-R39) says speedometers cannot show speeds less than the actual speed, and they must never show more than the 110 per cent of actual speed plus 4 km/h. So, under those rules, a car could be moving at 100 km/h, but the speedometer could legally display as high as 114 km/h.
For ordinary passenger vehicles, there’s no law in the U.S. that regulates speedometers, but U.S. manufacturers (and most Japanese as well) subscribe to a standard called
SAE J1226. Your speedometer reading must be within a range of plus or minus four percent off, but that’s four percent over the entire range of the speedometer, and that range can then be shifted in what’s called a bias.
Aslinda Amerikada ben sapma yok diye biliyordum, yanlis biliyormusum, ogrenmis oldum +/- %4 sapma varmis. Ama su var ki Amerikada sapma + yonde olabilirken, avrupada bu mumkun degil (kusura bakma direk kopyaladim buraya ama, tercume gerekirse yapariz hemen sorun degil)