If I have a clutch backing plate of unknown history but has obviously been machined for weight reduction and surfaced.....how may I measure to ensure that the same metal that has been removed from the friction surface, has also been removed from the three legs?

Is there a set of base measurements I use or take to check?

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

I think that height is supposed to be 1", but you are better off setting this height when setting up the clutch/flywheel etc. There are threads around on how to do this. Aim is to get the clutch diaphram spring "flat", and that is achieved by machining the horns.

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Steve

Mick, the original dimension is 25.0mm I think, but the only safe way is do a trial build with the flywheel, driven plate and drive straps.
This is because the flywheel face has probably been machined over the years too and this affects the result.
The diaphragm spring should be flat or very nearly so when assembled. I hold a 3mm twist drill against it, it should be parallel with the flywheel.
This gives maximum clamping force to the driven plate.
When the clutch is depressed, the spring goes over centre, reducing pedal effort and the force on the crank's thrust washers.

See http://www.minimania.com/web/DisplayID/ ... ticleV.cfm for Marcel Chichak's reasons why this is important.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Ok, thanks doc, certainly better on a case by case basis.
Having these legs a little longer would also lead to a later clutch up-take as well in my mind (with everything else in good order), is this right?

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Having the legs too long will give later takeup but maybe clutch slip.
It will also make the clutch feel heavier when pedal depresed.
My boss's 1275LS had clutch slip when the plate was only worn down 1.0mm. Years of backplate and flywheel machining (but not off the 3 ears) caused this.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.