Re: Speedometer error

[Mike Wattam <101714.1343@domain.elided>]

Peter, Andrew,Guy, other Digest members

It doesn't matter what gear you're in, whether the clutch is slipping or if
the torque convertor is not in lock-up, the speedo is positively geared
directly to the road wheels and will not vary due to any of these things. 
Refer to my earlier message about speedo head accuracy and
correct/incorrect diff ratio and tyre sizes.

Also be aware that measuring the height of the road-wheel centre from the
ground is most certainly not to be recommended as any way of measuring the
revs per mile, as the ROLLING radius is quite different from the STATIC
radius.  The only way of doing this accurately is to contact the tyre
manufacturer and ask him how many revs per mile for a new tyre of his make,
pattern and size.  This will be accurate.  

Mike Wattam
Triumph Stag Register