[s-cars] When clutch plate wears out, why does disengaging the clutch bec...

[Paul Gailus]

My understanding of the cause of a stiffer clutch pedal with a worn
clutch disk is along the same lines as Chad's comments.

When the clutch disk is new, the diaphragm spring in the pressure
plate assembly is typically nearly flat when the clutch is engaged.
When the clutch disk is worn thin, in order to get engagement the
diaphragm spring has to pivot so that its outer edge pushes the
pressure plate closer to the flywheel. The inner part of the diaphagm
and the tapered fingers (formed by radial slots in the diaphragm)
therefore pivot away from the flywheel. Because the diaphagm
is now dished instead of flat, it is harder to deflect, at least during
the intial travel of the clutch disengagement. Kind of like the bottom
of an oil can that is dished outward at the center.


> In a message dated 3/23/03 12:52:41 AM Central Standard Time,
> Paul.Park at colorado.edu writes:
>
>  My clutch is slipping and is due for replacement. I'm wondering
>  though, how does a worn out clutch plate cause the disengagement
> of the clutch to become stiffer/more difficult? How does this
>  translate into an engagement point that eventually finds itself
> at the end of clutch pedal travel?
---------------------

>  My theory on this is that when the disk gets thinner the geometry of the
> pressure plate fingers gets to a point where it requires more effort.
There
> is not a lot of travel in the pressure plate due to the low profile
design.
> . . . .
> Chad Tobin