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Smith Speedometers on Greeves road bikes

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  • Smith Speedometers on Greeves road bikes

    Following on from Pete Smiths article in LL198 listing the Smiths speedo types used on road models.
    I would point out these are just type numbers, on each speedo there is a gearing number usually in the 16** series. For each type there will be various calibrations depending upon the drive gearing, wheel & tyre size. the 16** number refers to revs per mile of the drive cable. It is important that the appropriate gearing number is used to get an accurate reading. It would appear that some fitted by Greeves were not the correct gearing number and as such the speedo gave an incorrect reading.

    To calculate the correct gearing number the formula to calculate turns per mile (TPM) for a given bike is:-
    TPM = 1680 x N divided by R
    N = number of turns of speedo cable to 6 turns of wheel & R = Radius of wheel/tyre in inches.
    After calculation you should get a number in the 1600 series. It needs to be within 35.
    (The info was published in The Classic Motorcycle March 1994)

    For some reason Smiths did not publish the all important gearing number for the instruments in their catalogue
    As for the later off centre needle, grey faced SSM2001/00 type instruments, these will fit any Greeves roadster and are interchangeable with the concentric needle black face instrument. Just a later design adopted by Smiths and used on many other makes including the BSA Bantam & Triumph Tiger Cub.
    I would add that should you wish to fit a different head lamp unit (I have a Yamaha one on my East Coaster) the grey faced unit by having an off centre needle pivot allows a bit more room for a larger light unit/bulb holder.
    Last edited by John Wakefield; 13/12/2017, 02:05 PM.
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