Smith's speedos, what head needs what gearbox?

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Onder

Onder

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I cannot find the references to tell what speedometer head goes with what gearbox. Anybody point me in the right direction?
 
Not really sure what your question is, but the Commando uses 1.25/1 gearbox with 1000 rev per mile speedometer head.
 
Sorry, to be clear: what does the code on the bottom of the face mean...how does one read it.
I know the the final number is the reduction ration 1600 uses 2:1 for instance. But the other
numbers tells us what?
 
Onder said:
Sorry, to be clear: what does the code on the bottom of the face mean...how does one read it.
Click to expand...

Each speedo (SSM) or tachometer (RSM) appears to have been allocated a number but with no apparent pattern or logical code only that the higher the number the later the speedo/tacho.

The number after the "/" denotes an upgrade or minor change to the original specification.
 
So no way to tell exactly what gearbox you need for a particular head?
 
Except for the 850 Mk3 (with the speedo drive gearbox on the drive side) all Commando speedos whether '1000' MPH or '600' KPH use a 1.25:1 (15/12) BG 5330/171 speedo drive gearbox.
 
I want to put a different speedometer head (still a Smith Magnetic), need to know what to drive it with.
ssm 5001/03 1600
 
"1600" MPH would use a 2:1 drive gearbox (with the correct drive cable rotation).
 
If only it were so simple as 2 dimensions. Add on the variable of axle diameter. I obtained this nifty catalogue/chart put out by Nisonger in 1972 which specs each Marque and model by the ID of speedo, tachometer, cable and gearbox.
It includes Ariel, BSA, Enfield, Greeves, Matchless, Norton, Triumph and Veloce.
I’m sure that the answer being sought can be deduced from the charts.
 

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