1275 gearbox- what speedo cable?

[moggiegeek]

I'm filling a 1275 gearbox with improved 1275 engine
What speedo drive arrangements do I need to make?
Final drive will be 3.9
Fitted with minilites.

[oliver90owner]

Check indication against a good sat nav and go from there?

Diff ratio changes, wheel size changing and tyre profile can all make a difference.

[Sleeper]

As above , drive for 10 miles or so and compare Satnav reading with Odometer reading...a little maths applied to the TPM figures ( usually four digits,sometimes three , on the speedometer ) should tell you what speedometer/tpm you're looking for.

John

P.S.
In the middle of re-building speedometer internals for Winter/Summer use.

[oliver90owner]

Depends on whether one wants the speedo or odometer to read correctly. They rarely agreed.

[Sleeper]

That's down to manufacturing tolerances,age and wear and can be re-calibrated out , the TPM figures are the figures to go by...

John

[IslipMinor]

What size tyres do you have fitted?

[Declan_Burns]

If you are fitting the T9 there are several different Ford speedo drives. You will have no way of knowing what was installed.
I make speedo corrector gearboxes and I always ask the customer to fill in a spreadsheet i.e. to do a comparison between the actual indicated speed and a GPS and check the tyre pressure beforehand. Then I choose the correction ratio and build the gearbox accordingly. These speedos are not linear over the whole range. The gearbox in the third photo sits on the back of the speedo. I have built quite a lot of them for MG's.

Regards
Declan

[moggiegeek]

Thanks for the advice re calibration.
Its a mg 1275 box so at a very simple level I wondered could I use the standard 1098 cable and drive?
Thanks

[moggiegeek]

Thanks for the advice re calibration.
Its a mg 1275 box so at a very simple level I wondered could I use the standard 1098 cable and drive?
Thanks

[IslipMinor]

The speedo cable itself is the same for any of the in-line A-Series gearboxes fitted to a Minor.

The tyre size and diff ratio will affect what tpm (turns per mile) are required in the speedo head.

What tyre size are you using?

[moggiegeek]

Ah thats great now I know cable is standard
Im a way off calibration with only a 1275 engine with some dun bits to build up as well as fitting a variety of mods over the winter