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spider rust
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VBMWMO #8708
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Is the instrument marked in anyway to specify solo or sidecar application.
Does anyone know?

schrader7032
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VBMWMO #7032
San Antonio, TX
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I was just thinking...why

I was just thinking...why would a tachometer care about gearing? It's reading crankshaft revolutions per minute which is affected by your right wrist, not the gearing in the transmission or final drive or if there is a sidecar attached. Seems to me the answer would be no.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Darryl.Richman
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Deutsch v. English

Kurt, in German a speedometer is a Tachometer and a tachometer is an Umdrehzahlmeter (marked in UPM, Umdreht pro Minuten).

It's very confusing.

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Darryl.Richman
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Now, to the question

Most German speedometers are marked with a W number (Wegzahlnummer). This is the ratio of the number of turns of the rear wheel (assuming the usual BMW arrangement of having a speedometer take off from the transmission output shaft) to a unit of distance shown by the odometer (in km or miles as appropriate). This number assumes a certain wheel size and final drive gearing, so the correct W number is not affected by having a solo vs. sidecar transmission, but is affected by the difference in sidecar gearing.

Usually the W number appears on the face of the instrument, and often it is also stamped into the case. If the instrument has been updated for a change, you may see the original number on the face scratched out or painted over and a new number added, and the same may appear on the case.

I have seen various tables showing final drive gearing and distance km/miles to W numbers, but I don't recall where. I'm sure a quick Google would find it.

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schrader7032
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VBMWMO #7032
San Antonio, TX
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Well, never mind! That

Well, never mind! That certainly is confusing...I'll have to try and remember that.

Here is one discussion of Wegdrehzahl, which according to the article, is this relationship of turns versus distance:

http://bmwvmca.org/joomla/index.php?option=com_content&task=view&id=118&...

Google translates Wegdrehzahl as "characteristic coefficient"...sort of works??

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'78 R100/7 '69 R69S '52 R25/2

spider rust
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Tachometer gearing

Darryl's reply confirms my belief that when the machines were delivered the Tachometer was geared for solo.
I understand the gear ratio fitted, for example to this instrument is 1.75, and that is solo.
The other inscribed number would be part or manufactured number? I think?

I know to work out what the reading should be is to roll the machine a set distance and note the number of cable turns.
This will give you speed but may not be accurate for long distance.

Does any other member have an original Tachometer with original dial plate.
And if so it would be interesting to learn about the gear ratio and speed accuracy for that instrument.

  • veigel_tachometer.jpg
spider rust
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Tachometer gear ratio reply correction

I am wrong the 1.75 is not indicative of solo. Darryl has correctly described what it represents. Although I saw this ratio described as solo on another site. But its interesting to clarify my question regarding if the motorcycles were fitted with solo or side car geared Tachometers.

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