"The Natural Philosopher" wrote in message
...

I think you will find my speedo is calibrated to be correct within 1
mph. 8-)

I seriously doubt it, because the wear on your tyres and the temperature
of them will make more difference than that.

Not to mention substituting a different make. Rims are exact. Tyre outside
diameters are not.

Who said it was mechanical?

Bye.