Hi all.

John at Mini King has told me that all Aussie mini speedo worm and pinions are the same, but didn't tell me what the tooth counts were. I've just taken this pair of gears out of my Metro gearbox, and found 5t / 18t - which, according to the online calculator at www.tomsminisite.co.uk, will make for a 30% error - clearly no good. So my current plan is to just put the standard Aussie one in - but what is it? 6t / 17t?

If anyone is interested in my 5t / 18t combo, I suspect it will soon be for sale - not sure who might have an application for it though!

Thanks a lot for any opinions or advice.
Matt

17 and 6 is the standard Aussie ratio.

Thanks for cyber-quick reply!
Will it be possible to get a 7t worm or a 16t pinion, to get me closer to the calculated best, other than to buy new? I think a new worm or pinion would be quite expensive, but a better option than speedo recalibration, which I hope to avoid altogether.

(The calculator referred to in my original post suggests that 6/16 or 7/17 is a bit better than 6/17.)

thanks
matt

It should be easy to get a second hand speedo drive, I am sure that there are plenty around. But they are all 30 or more years old and the pinion gears have a habit of splitting.

I know very little about the speedo drives in Minis. All the car for the first 20 or so years used the same drive ratio with different speedos to allow for the different tyre size and diff ratios.
Some time in the early 80s they changed to different ratio speedo drives.

I am about to change the speedo and diff ratio in my 1100 and I am also looking for an easy way to get the speedo right.

I can recommend a look at these two sites for speedo calcs, but you'd do well to validate what they tell you:

http://www.guess-works.com/Gearbox/Technical/ratio.htm

(Shows true speed, then indicated speed in brackets when you finish the inputs)

and

http://www.tomsminisite.co.uk/speedo_calculator.php

(Doesn't show all of the worm / pinion combinations possible)

Neither are perfect, so if anyone else knows of others, or the actual mathematics for working it out, please post here!

Toms site does not have the diff ratios used in the Aussie 1100 and does not seem to have the speedo turn per mile that I have.

The other site does not include the tyre size that I have.

I don't know what to suggest - more googling?

I will just do what I always have done, work it out on a bit of paper!

Can you share the formula?
Something like wheel radius / diff ratio / worm & pinion ratio / speedo head setting?

I will share the formula when I work it out, it may take a while, don't wait up.

Just for those who may not know this, On most speedos there will be a number, For instance a Mini 850 has 1408, from memory a Cooper S has 1280 and so on, some speedos may have 1280rpml some may have rev per km, what this represents is say with the 850 at 1408 revs the speedo should read 60 Mph, this is the same for Mph Or kph what ever the number is, At that revs the speedo should read 60, I am not sure if this helps. I hope it does

you could just get your speedo recalibrated to match the drive you have. There are some details you need to provide - like number of turns the speedo cable makes per revolution of the wheel and the distance the wheel travels in one revolution. and take those along with the speedo to a place that calibrates them and they will do the rest.

_________________
David L


My greatest fear in life is that when I die my wife will sell my Mini and tools for the price I told her I paid for them!

Speedo calibration isn't nearly as attractive - to calibrate the needle side of the speedo only is $200 at my local shop, and leaves the odometer reading incorrectly. To fix both the needle and odometer is $400 at my local shop. Fitting the 6/17 combo gets me close, perhaps close enough.

Matt