[T3] Speedometer/Odometer ratio?
Jim Adney
jadney at vwtype3.org
Thu Feb 9 11:00:18 PST 2012
I believe that all US cars have speedometers that expect 100
revolutions of the speedometer cable per mile of distance traveled.
To get this right, appropriate speedometer drive gears are installed
in the vehicle transmission at the factory, and the speedometer cable
gets its drive from a special connection on the side of the
transmission.
VDO does this differently. On the back of every VDO speedometer there
is a stamped number which I believe is the ratio that makes this
speedometer/odometer correct for this car and tires. All the Type 3
speedometers I've ever seen, which get their drive directly from the
front wheel, have either W0.80 or W0.82 stamped there. I assume the
small change might have come with the introduction of radial tires,
or it's possible that VW just made a minor correction at some time. I
really haven't noticed whether this was a change that happened at one
particular time or if they started getting mixed at some point.
I also have a VDO speedo out of a Mercedes, and that is marked W1.47.
Those cars got their drive from the transmission.
So here's my question: What does the W0.82 mean? (I just measured the
diameter of my tires, and they are about 0.65 m. Not even close to
0.82.)
Does anyone know what this means?
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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