11 replies to this topic

[Danuneek]

Ok, where to start. Not only is my new/old centre speedo making a bad buzzing sound (speedo mechanism inside must be rusty) but its speed is out as well so it would need calibrating. Now im looking at new speedo's and have just discovered that I need to get a particular speedo that is geared to my final drive. So I need to find out what final drive actually is and what the final drive for a 93 Spi Cooper would be. It's been tampered with too, 13/7 wheels, stage 1 kit and HIF 44 SU carb. I dont know whether this would make a difference? I need some advice because I've worked hard all week converting from a 3 clock gauge to a centre speedo, spraying, wiring a harness, speedo cable etc... to find the mechanism in the speedo is going.

[pyromaniac_yeti]

i belive the final drive on the injections was sposed to be 2.7-1 not sure. maybe someone else could confirm.

there was a speedo calculator out there somewhere aswell. think its in guessworks signature. that'd give you all your answers

[matt615]

You don't need to change the speedo. You need to change the speedo drive gears in the gearbox.

[ZED]

or if your lazy like me, follow someone and get them to give you the fingers (3 for 30 etc) and if your lucky, the kmph actually read the right speed!

or speedy cables web site give you a formula to work it out and they can recalibrate your speedo, costs about £60.

Zed

[Danuneek]

Im largely changing the speedo not solely because the speed reading is wrong (which it is) but because its making an horrendous noise. I stopped and unscrewed the speedo cable to see if it was the cable or the speedo and the noise stopped which suggests the mechanism inside the speedo is a bit old. I was trying to save money buying off ebay, but didn't realize there were different speedo's for different drive ratios. The SPI is a 3.2, but thats with 12 inch wheels. Mine has 13 inch. I dont really want to risk buying another knackered one so im thinking of getting a new one from mini sport and getting them to calibrate it. Thats unless someone has a suggestion on how I can fix this noise?

ps. Zed, tried that and it reads 30-27, 40-35, 50-43, 60-51, 70-60.

Edited by Danuneek, 22 October 2008 - 11:45 PM.

[Ethel]

I'd go off the odometer to calibrate the speedo (drive a known distance), particularly if there's a chance it's inaccurate anyway. You could swap over the speedo innards with pretty much any Smiths gauge. GuessWorks has loads of speedo info on his gearbox site.

[Guess-Works.com]

In summary....

You have an SPi cooper which will be running a 3.2 final drive as Std...

13 or 12" wheels does not really matter as the rolling distance of the std 12" tyre is not that different from the 13" tyre.

The speedo ( which I assume is a pre 1984 smiths central clock ) will have the tpm figure written under the odometer ( probably 1280 if it's a 90mph speed which is not off an 850 )

All that taken into account you want a 6/15 combination for the gearbox speedo worm and pinion... I believe I have both of these here.

This will make your speedo read slightly fast ( approx 1% error ) which is ideal.

[Danuneek]

In summary....

You have an SPi cooper which will be running a 3.2 final drive as Std...

13 or 12" wheels does not really matter as the rolling distance of the std 12" tyre is not that different from the 13" tyre.

The speedo ( which I assume is a pre 1984 smiths central clock ) will have the tpm figure written under the odometer ( probably 1280 if it's a 90mph speed which is not off an 850 )

All that taken into account you want a 6/15 combination for the gearbox speedo worm and pinion... I believe I have both of these here.

This will make your speedo read slightly fast ( approx 1% error ) which is ideal.

That sounds great, how would I go about fitting the gearbox worm and pinion and have you come across speedo's making a poorly sound and if so, what can be done?

[Guess-Works.com]

Replacing the speedo drives can be done in car but it's a little fiddly...

Firstly remove the radiator, then you will need to remove the n/s engine mount and bracket ( support engine with blocks or trolley jack )

You will then have access to the engine mount adaptor on the side of the gearbox, which again needs to be removed... once off you can see the end cover for the speedo worm. remove cover and withdraw worm.

The pinion is where the speedo cable is connected, so remove speedo cable, then undo bolt and remove speedo cable adaptor. you can then remove the worm..

as for the moise coming from the speedo, sorry can't help much there... it's possibly just surface rust on the rotating parts and may well wear off...

[Danuneek]

Replacing the speedo drives can be done in car but it's a little fiddly...

Firstly remove the radiator, then you will need to remove the n/s engine mount and bracket ( support engine with blocks or trolley jack )

You will then have access to the engine mount adaptor on the side of the gearbox, which again needs to be removed... once off you can see the end cover for the speedo worm. remove cover and withdraw worm.

The pinion is where the speedo cable is connected, so remove speedo cable, then undo bolt and remove speedo cable adaptor. you can then remove the worm..

as for the moise coming from the speedo, sorry can't help much there... it's possibly just surface rust on the rotating parts and may well wear off...

It sounds straightforward but difficult, i'll see what my dad ses. If im buying a new speedo to eradicate the noise, perhaps it would be easier to buy a clock that is already calibrated to my car. Do you know if the Cooper S speedo's that are geared to 3.44 final drive would be alright in my car with a 3.2 without any adjustments, would it just be a matter of been a little quicker?

Edited by Danuneek, 23 October 2008 - 05:04 PM.

[Guess-Works.com]

No it wouldn't

The cooper S speedo will still be a 1280 tpm clock, therefore you will be in exactly the same situation as you are now..

[Danuneek]

No it wouldn't

The cooper S speedo will still be a 1280 tpm clock, therefore you will be in exactly the same situation as you are now..

Thanks, one last question, do you know what SN code or tpm I would require for a 3.2 on 10" and a 3.2 on 13"?

Edited by Danuneek, 23 October 2008 - 10:59 PM.