questions for upgrades in 1275cc Minor

[Declan_Burns]

If a 1625 speedo under reads then he will need a higher TPM not a lower.
One of my corrector gearboxes could be used but 10% change means larger gears.
The photo shows one of the new generation boxes (1:1.4) with a 3D printed housing.
Regards
Declan

[Mogs]

Thanks Declan. I've various speedos in my workshop with assorted codes (albeit mainly classic minis) so will first experiment to see whether any of those are closer.

[Mogs]

Just thought.... Perhaps I can use a 90mph face only, to replace my 80mph one. The speeds' positions look as if they'll address the original's under-reading (pity it'll then be a mix of black and silver colours, but easy to do!?).

[Declan_Burns]

Mogs,
Why not-an easy way out!
Regards
Declan

[Sleeper]

Declan

" If a 1625 speedo under reads then he will need a higher TPM not a lower. "

A 1625 speedo needs 1625 turns to show 60mph ( or 1 measured mile )

His is under reading ie. showing for example 50 mph at an actual 60 mph , he is getting less turns per minute/mile than before..

so

He needs either a faster input to show the same speed ( back to the original diff ) or a speedometer that shows 60mph at a slower input ..

1462 tpm ?

John

[Mogs]

I've nearly finished installing a 90mph (black) face to replace the original silver 80mph face. The resulting speedo looks a bit odd with silver centre and fuel gauge but it's worth a punt to see if it reads anywhere near accuracy! At a glance the reading should certainly be better than 10% under. I'll finish and test it with GPS tomorrow. I'd put additional Smiths Oil, Water, etc gauges in a triple pod under the speedo previously, so it doesn't look too incongruous, provided it works...
Onward and upward!
Richard

[Sleeper]

I think the black faced speedos range from 1248tpm to 1504tpm so the result should be better..

John

[Declan_Burns]

Declan

" If a 1625 speedo under reads then he will need a higher TPM not a lower. "

A 1625 speedo needs 1625 turns to show 60mph ( or 1 measured mile )

His is under reading ie. showing for example 50 mph at an actual 60 mph , he is getting less turns per minute/mile than before..

so

He needs either a faster input to show the same speed ( back to the original diff ) or a speedometer that shows 60mph at a slower input ..

1462 tpm ?

John

Yes John you are correct-another one of my senior moments
Regards
Declan

[Mogs]

With reference to the under-reading speedo, I took the easy way out. I've replaced the 80mph face with one from a spare 90mph speedo head. I tested it with GPS this morning and the result is a satifactory fix. Instead of the original 10% under-reading because of my higher ratio diff, the speedo now reads closer to 10% over. Bearing in mind these old speedos typically read 5 to 10% over by default and registering "over" is safer than under, I'm happy with the result. The photo shows what the head now looks like. Not ideal but not too incongruous against the Smiths supplementary gauges in the pod below.
Thanks for the other ideas offered, anyway.
Richard

[oliver90owner]

It is illegal to have a speedo that reads under - or at least it is not legal to supply a new vehicle that way. That is why all original car speedos are over optimistic on the indicated speed. Basically allowed +10% and no negative error to be legal - although you should know your actual speed for the law.

[Mogs]

Absolutely. UK Authorities in some Police areas are apparently no longer giving drivers a 10% tolerance so apart from needing a speedometer that is at least over-reading, drivers need to know by how much. The average speed camera zones are also critical. I use a Sat-nav as a back-up/safeguard and at least the speedo on my Minor reads "over" not "under" now! As a member of the I.A.M. since 1979 I'm not anxious to be caught out.