Speedo mileage adjustment

[hdavy]

I am going to change my speedo for one that I have spare, but this one shows much lower mileage. I want to reset it to match true current mileage. Friends told me 'easy just take the back off and you can get at the numbers' . So you can but only the trip will shift and it would take more time tha I have left to wiggle it round that way. Any ideas.

[beero]

Why change it? Just photograph both speedos side by side , you then have evidence of the speedo change and the mileage change.

[chesney]

It is certainly more complicated than that! If you turn them by hand you will damage the pawl and gear.

[ian.mcdougall]

If i remember correctly i think if you start at the right hand end of the odometer and turn the number ring forward to half way between 9 and 0 and set them all the same way you can then start on the left hand end and set your mileage to the old odometer but do this at your own risk as I may just be having a flash of a past life that is all in my own mind as a test use the old speedo to see if it works ( I seem to remember as a child playing with old speedos and setting them all to zero ) it might even be the other way around. Please ignore these ramblings if nobody has done or heard of this before
yours written with a crayon and transcribed by the nurse/guard
Ian

[chesney]

I have zeroed these speedos and they must be taken completely apart to avoid damage to the pawl gear. Alternative, stand there for a long time with an electric drill and a speedo cable

[bmcecosse]

As above -high risk of doing damage.....I would leave well alone....... Is the new speedo same tpi as the old one?

[mike.perry]

The small Series MM/II speedo mileometer can be adjusted, never tried a large speedo

[chesney]

How I ended up doing it

[bmcecosse]

Crikey.....

[IslipMinor]

The Toyota box has a very different skew gear ratio to a Minor, so we needed a speedo head with 1000 tpm, which just happens to be the Series II standard! I took the head out of the casing, but not completely apart as Chesney did, and after some careful fiddling reset the mileage to the same as the old speedo. That was nearly 15 years ago, and still working well.

[charlie_morris_minor]

if anyone reading this thread wants a pdf manual on stripping a speedo drop me a PM with your email address

[hdavy]

Hmm. Thanks guys. I think I'll probably leave well alone, however Chesney how long would I have to use the drill to clock 50K miles?

[IslipMinor]

If you assume it is a 948 speedo that is calibrated for 1504 turns per mile (tpm) and the drill, which has to run in reverse, is running at around 1,500 rpm, it would take 50,000 minutes, or 833 hours or 35 days or 5 weeks!! Makes you wonder how many drills it would need - would one last 833 hours of continuous running?

Is the drill idea is a bit of a myth, at least for major mileage adjustments?

[chesney]

The drill idea works. It was sort of a joke, not really a feasible idea unless you're something like 5 miles from the figure you want.

[JOWETTJAVELIN]

I had the exact same problem, speedo showing 24k when reality was 88k. Now it CAN quite easily be done, but it is a very delicate job.

Remove the speedo, carefully prise the chrome surround and glass off by bending the flanges with a screwdriver. Next unscrew the small plastic nut holding the indicator needle on, taking care not to move the needle excessively, especially backwards. Remove needle by pulling off. Take out the two tiny screws on the small circular face disc and put them in a very safe place. Also remove the outer speedometer face.

This reveals the odometer and if I remember correctly you can start from the right hand side and move each number slightly to the right, thus disconnecting from the drive and enabling it to turn freely to the desired position. Then move onto the next number until the job is complete, making sure each number clicks back into place. Test by attempting to turn each number gently - they should be locked into position.

Note that when reassembling the speedo needle may be out of calibration due to being removed - I overcame this by driving past one of those flashing road signs which gives your speed, and noting the discrepancy on the speedo before adjusting the needle by X miles an hour. It has been bang-on ever since.