
Originally Posted by
QuaTTrings
Apparently a new Federal law was passed in the late nineties that allows for up to a 5% deviation from the actual speed. Manufacturers are much more likely to have speedometers that display a higher speed than actual, rather than a speed that is actually slower than what is displayed. There is more information on this on the NHTSA site as well as Deparment of Motor Vehicle websites. IMO it is unlikely that the S5 posted above was "actually" doing 163 mph unless on a grade or with a tailwind. The limitation for the S5 in Germany is 155mph
Yes, I am aware of the law, that's why I corrected your claim that the law mandates a higher speedometer reading than actual speed.
As I wrote, the law asks for accuracy with allowance for variance.
The deviation is to allow for manufacturing variance.
The law is for accuracy not for higher than actual. Under the law a speedo can also read lower than actual as long as it is within the deviation spec. Manufacturers are likely to comply with the law, but they do not make the speedo read higher for any other reason.
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