My speedo (Rover 213 dash) reads very much on the high side. Short of dismantling the final drive, I have no idea of what ratio it is, neither do I know what speedo drive ratios are fitted, and on top of that, I don't know whether a the drive ratio required for the Rover 213 speedo is different to the one required for the Metro speedo.
On top of that, I'm thinking about fitting a digital dash. What do they use to determine the car's speed, is it a speedo cable or some form of electrical/electronic transmitter?