> I believe my calibration is off, can anyone explain how to match
> the correct
> speedo with the car? How do you ascertain the car ratio and the
> speedometer
> ratio to determine the correct part?
There are instructions at
http://mywebpages.comcast.net/rhodes/speedo.html
In a nutshell, find the "turns per mile" of your tires, usually available
from the dealer, like
http://www.tirerack.com/tires/Spec.jsp?make=Kumho&model=Euro+Metric+771
multiply by your differential ratio (usually 3.7 for a TR4A)
and divide by the speedo drive gear ratio (2.5 for a stock TR2-early TR6
gearbox).
That will give you the calibration number that should appear on your speedo.
Of course there won't be an original speedo with that number (they didn't
match exactly even from the factory), but comparing the numbers will give
you the relative error.
Randall
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