Morris Minor Owners Club

How do you work out the speedo turns per mile?

My Minor has a Marina rear axle and T9 Ford g'box and runs on 13" marina wheels

It all depends on the final drive and tyre size. On 948/1098/1275 boxes the speedo drive gear is the same ratio and the top gear ratio is 1:1 so you can compare the diff ratios.
There is a website http://www.etyres.co.uk/tyre-size-calculator.htm