In article . com>,
says...
>A common defense against pacing I found is to challenge
>patrol car's speedometer's calibration.
>What kind of inaccuracy are we talking about here (i.e. in
>maybe 1-2mph, or up to 10mph)?

Insist on seeing the calibration certificate.

>And what is the relationship
>between tire pressure, wear and tear vs. the speedometer's
>calibration? Where can I learn more about it?

Low tire pressure and tire wear will all make the tire smaller. So the cars
real speed will be lower than the speedometer is reading. You should also
ask if the tires on the car when the speedometer was last calilbrated are
the same as the ones that were on the car when you were clocked. This time of
year many police cars switch to snow tires and that could affect the
speedometer calibration. Snow tires tend to be taller than summer tires and
the car will be traveling faster than the speedometer reading. You should try
to get this information before the trial so that you can properly prepare a
defense.
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Alex