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Speedo - how to read the numbers

I'm saw this kilometers speedo and would be interested to understand the small numbers on the dial.


Maybe this one is usable for my ulster with 4-speed gearbox.

thanks, Oliver

Hi Oliver,

Michael Flannery at Smiths Magnetic and Governor Speedometers on Facebook may be able to decipher the number code. You'll need to join the Facebook Private Group to take part in discussions.


The figure of interest is the number of turns per mile, which you need to match to your specific car (considering axle ratio, tyre size etc). Typically for an A7 the number will be something of the order of 1040 tpm.

If incorrect, a professional repairer can re-calibrate it within certain limits. 
Speedograph Richfield publish a method on their website to take the appropriate measurements.
They also sell (not inexpensive) external gearboxes to step the input up or down as needed. 
Others here have made their own though I don't know with how much success. 

Or like the rest of us you can just learn to factor the indicated speed as needed. Those solar-powered speed reminder signs they have on the outskirts of villages are invaluable here, and have enabled me to drive considerably faster than I used to.

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