Speedo change

[tedlogan]

Does anyone know if its legal to change a speedo? Im restoring my Traveller and like the look of the black speedos. Would I have to the the milage to that of the old one? If so ho do you do it? Will there be any problems with changing over? Thanks Ted

[charlie_morris_minor]

legally there is no problem changing a speedo, unless of course you reduce the mileage and then claim it is the true mileage.

the only problem you will have is finding a black speedo which has the correct TPM to match your axle. idealy you will need to find a black speedo which has the same tpm as you have on your gold speedo.

[mike.perry]

What engine/box/axle do you have in your Traveller?
If it is a '63 1098 then you can fit a later black speedo with a 1408 TPM
If it is a 948 with a 1504 TPM then you can fit a black speedo out of a 1098 LCV with the same TPM as that uses the same 4.55 axle

[bmcecosse]

It is possible to 'adjust' the mileage on the odometer - I understand you need to slide feeler gauges in between the number dials then twiddle them round carefully with CLEAN fingers until it reads what you want. There are also various Mini black speedos that fit - with different TPM numbers to suit different final drive ratios.

[charlie_morris_minor]

I understand you need to slide feeler gauges in between the number dials then twiddle them round carefully

ah! that i should have done it when I set the mini speedo to zero.. i just used my fingers to separate the wheels.. was not very easy but it worked

[tedlogan]

What does TPM stand for and how do I work out what my current Speedo's TPM is? Also would I set the new speedo to the shown mileage of my current speedo or reset to 0? Thanks

[mike.perry]

TPM = Turns per Mile. It is the four figure number on the dial next to the serial no.,1504 in the case of a 945/4.55 diff, 1408 for a 1098/4.22 diff.
There is a chart on the Series MM website under car ident. http://seriesmm.mmoc.org.uk

[fussyoldfart]

TPM is Turns Per Mile and refers to the number of turns of the cable per mile travelled. This reflects the turns per mile of the wheels, the final drive ratio of the differential and the ratio of the speedometer drive in the gearbox. The speedometer itself will be geared to convert the TPM into MPH and also miles travelled.

Most manufacturers provide instruments that are a bit "optimistic" regarding MPH and try to be realistic about miles travelled. You can look up the turns per mile/kilometer for the tire size you have and the gear ratios are listed somewhere in the shop manuals to let you do the arithmetic. (Perhaps someone here knows exact chapter and verse reference for this information.)

The right instrument for your car will be the one that comes closest, you may not get it perfect. If your car has radial tires, for instance, they probably make more turns than the original bias-ply tires so you may appear to be going faster/farther than you really are.

For my own car I bought an electronic replacement that can be calibrated precisely by pressing a button, driving a measured distance, and pressing the button again.

Now you all know how I got to be called fussyoldfart

Darrell McDonald