Michael,
The speedometer's odometer function is a direct mechanical wormgear -
pawl/ratchet and where tire size (radius) will affect the miles covered..
There is a 4-digit number on the speedo face (1120 on mine) that gives the
number of input cable turns it takes to register 1.0 mile. This is
mechanically fixed.
The speed part uses a magnetic bar to create a magnetic field that
deflects a metal plate that has the needle attatched to it. The speed part
can be affected as both magnetic bar and return spring lose strength over
time. You can carefully take the thing apart and change the position of the
needle relative to the plate, giving a little adjustment in speed
calibration. I think the only way to change the odo part is to put in
different gears, which seems pretty involved.
I've opened my tach and speedo up to clean and lightly lubricate. Your
speed part seems very accurate as is!
Jeff
CF13816U
----- Original Message -----
From: <SamuelsMA@aol.com>
To: <6pack@autox.team.net>
Sent: Sunday, April 30, 2006 4:44 PM
Subject: Speedometer/Odometer
> My question is, why would our speedometers agree almost perfectly, but our
> odometers be different by 4%? Also, is 18 mpg (or really 17, when you
> take
> the odometer inaccuracy into account) in mixed driving (but plenty of
> highway at
> about 65 mph) similar to others with similarly modified, non-overdrive
> cars?
>
> Thanks!
>
> Michael
> '76 Tahiti blue
> CF 57044U
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