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To clarify that last bit a little:

'Back in the day' when mechanical clutch linkage abounded, you'd have to occasionally crawl up under there and adjust the pedal freeplay, because the more the clutch plate wore, the less the clutch pedal would properly disengage it.
 

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Discussion Starter #22
To clarify that last bit a little:

'Back in the day' when mechanical clutch linkage abounded, you'd have to occasionally crawl up under there and adjust the pedal freeplay, because the more the clutch plate wore, the less the clutch pedal would properly disengage it.
Yup and mine is "self adjusting" hydraulic, not mechanical, not sure where this all fits into the distance from flywheel to pressure plate disc sits...
 

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And yet, if I bought, and I have, a new pressure plate and clutch, the distance will be closer to a new flywheel
But it wouldn't, as the flywheel would be within that spec from the shoulder to the friction surface.

It's not the overall thickness of the flywheel that the spec provides, it's the distance from the machine face where the pressure plate rests to the friction surface is.

If it's .88" new, and you machine .010" off the pressure plate mount surface and .010" off the friction surface, then the distancer is still .88" ;)

If you got a new pressure plate and the distance was significantly closer than what you pulled off, then it's far more likely the pressure plate was well worn, had been turned too much at some point, or had really worn out springs.

Not a super big deal, but it would make a modicum of difference in the amount of pressure applied to the clutch disk, and may eventually even cause slippage under extreme driving conditions.
 

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Yup and mine is "self adjusting" hydraulic, not mechanical, not sure where this all fits into the distance from flywheel to pressure plate disc sits...
It doesn't. :)

It's strictly a system that allows the clutch pedal to operate correctly regardless of clutch plate wear without the need to deal with tools to do it.
 

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Discussion Starter #25
It doesn't. :)

It's strictly a system that allows the clutch pedal to operate correctly regardless of clutch plate wear without the need to deal with tools to do it.
Then what does that have to do with 22.5mm +/- .2mm spec you provided?
 

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Nothing.

The specs have to do with the distance the pressure plate face is from the flywheel face, and by virtue of that the pressure on the clutch plate.

Again, all the self adjusting does is make sure that when you push the clutch pedal, the clutch fork moves the throwout bearing the correct amount and thus allows for proper disengagement of the clutch (almost) regardless of the amount of wear on the disc.

The 'self adjusting' part is from the master cylinder to the slave cylinder and acts on/is limited to the fork.

The machining specs ensure that the flywheel friction surface and pressure plate friction surface are within a specific distance, which in turn ensures that the pressure plate squeezes the clutch disc to the face of the flywheel with enough force to provide proper function.

For all intents and purposes, they are two totally seperate things which have seperate functions that just happen to be connected to each other.
 

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Discussion Starter #27
For all intents and purposes, they are two totally seperate things which have seperate functions that just happen to be connected to each other.
I'm still lost. If you had those specs and had your flywheel and pressure plate turned (which is in the Alfa manual to have them turned) you'd upset that .2mm difference allowed unless you magically could place metal instead of removing it or by adding shims, which is not mentioned or even sold...
 

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I don't see where turning the pressure plate is in any of my books.

Replace it, sure, turn it, no, not in anything I've got, seen, or heard of. :shrug: (I wouldn't even if it were there as machining the pressure plate face would definitely screw up things as far as the spring pressure applied and the specs for the flywheel)


That .2mm/.010" is simply the tolerance level on the machine work.

If the ideal is .88mm from the flywheel friction face to the machine face where the pressure plate mounts, then with that .2mm spec, the distance can vary from .86mm to .90mm and still be considered useable, safe, and correctly machined.

Shimming would very likely push it out beyond spec leaving you with a slipping clutch at some point soon down the line.

Ignore the self adjusting clutch pedal system, it's not specifically pertinant to the flywheel machining operation and thus pressure plate fitment.

(yes, it's important, but not to the topic at hand)
 

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Discussion Starter #29 (Edited)
I don't see where turning the pressure plate is in any of my books.

Replace it, sure, turn it, no, not in anything I've got, seen, or heard of. :shrug: (I wouldn't even if it were there as machining the pressure plate face would definitely screw up things as far as the spring pressure applied and the specs for the flywheel)


That .2mm/.010" is simply the tolerance level on the machine work.

If the ideal is .88mm from the flywheel friction face to the machine face where the pressure plate mounts, then with that .2mm spec, the distance can vary from .86mm to .90mm and still be considered useable, safe, and correctly machined.

Shimming would very likely push it out beyond spec leaving you with a slipping clutch at some point soon down the line.

Ignore the self adjusting clutch pedal system, it's not specifically pertinant to the flywheel machining operation and thus pressure plate fitment.

(yes, it's important, but not to the topic at hand)
Now I got you! I thought you were saying the distance was from the flywheel to the pressure plate disc. You are giving, basically, specs on how much a flywheel is allowed to be turned before needing a new flywheel, same applies to brake rotors, minium thickness parameters...I see what you were talking about now..."Both surfaces" being the mount of the pressure plate to the flywheel and the clutch surface of the flywheel. Now I got you! Yes my shop did do that, hence the charging of $5 for each pin they had to pull and then replace afterwards.
 

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Nope, that's something else but I don't readily have the spec for that. LOL

When you had your flywheel off, it had a raised machine faced edge all the way around it where the dowels for the pressure plate went, right?

The specs I listed were for the distance from that machined face to the machined friction face of the flywheel.

When either the friction surface or that ridge is machined, usually the other needs to be too so as to maintain that spec distance so the pressure plate applies to correct pressure to the clutch disc.

If you turn the pressure plate, then that flywheel spec goes out the window as you'd have to start with the baseline .88mm +/-, then subtract the amount taken off the pressure plate to get things back in sync with each other.

EG:

Flywheel spec is 22.5mm +/- .2mm

You get it machined so that it ends up that way.

Now, you take the pressure plate in and get 1mm taken off it.

When you bolt it together, the distance from the pressure plate friction face to the flywheel friction face has grown 1mm, (because the pressure plate is now thinner) which means you'd have to take the flywheel out again and knock 1mm off the pressure plate mounting surface of the flywheel, but not the friction surface to get everything back in sync.
 

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Discussion Starter #31
Nope, that's something else but I don't readily have the spec for that. LOL

When you had your flywheel off, it had a raised machine faced edge all the way around it where the dowels for the pressure plate went, right?

The specs I listed were for the distance from that machined face to the machined friction face of the flywheel.

When either the friction surface or that ridge is machined, usually the other needs to be too so as to maintain that spec distance so the pressure plate applies to correct pressure to the clutch disc.

If you turn the pressure plate, then that flywheel spec goes out the window as you'd have to start with the baseline .88mm +/-, then subtract the amount taken off the pressure plate to get things back in sync with each other.

EG:

Flywheel spec is 22.5mm +/- .2mm

You get it machined so that it ends up that way.

Now, you take the pressure plate in and get 1mm taken off it.

When you bolt it together, the distance from the pressure plate friction face to the flywheel friction face has grown 1mm, (because the pressure plate is now thinner) which means you'd have to take the flywheel out again and knock 1mm off the pressure plate mounting surface of the flywheel, but not the friction surface to get everything back in sync.
New pressure plate, no need to have that disc touched, it is set at factory thickness. I fully understand what you were saying though, yes, mine is at spec now.
 

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yes that was what I ment by both surfaces the part the disk rubs on and the part the pressure plate bolts to. The pressure plate has a stop so it will not wear to far(it should stop and start to slip before it hits the rivits. But if you just cut the inner part where the disk slips and not the outer too then the stop will engage too soon and you will start slipping when there is a lot of meat left on the disk.
 

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:rolleyes: Leave it to Jim to get all technical on us with the drawings

;);)
 
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