[T3] Speedometer/Odometer ratio?

Brian Fye bfye at canyonville.net
Thu Feb 9 11:03:34 PST 2012


i would expect that to mean their version of a 'final drive' ratio.  Could
very much be that for every revolution of the wheel, you get .80 or .82
turns of the final gear in the speedo.

On Thu, Feb 9, 2012 at 11:00 AM, Jim Adney <jadney at vwtype3.org> wrote:

> 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?
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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-- 
Brian Fye
Canyonville Christian Academy
541 839 4401 ext. 110
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