Techie clutch question

[wheeljack888]

Morning PHers

A question for all you engineers out there. I've just removed the clutch from my 4.0 and I seem to have uneven wear on the friction plate.

The pressure plate rotates with the flywheel and as the clutch pedal is brought up the friction plate is axially clamped by the pressure plate to the flywheel face. Therefore there is no relative movement between the two clamping faces. With this in mind how come the flywheel side of the friction plate has worn faster than the pressure plate side?

Any thoughts will be much appreciated.

[incorrigible]

How much faster, what are the relative thicknesses

I've never seen completely even wear, could be a case of "they all do that sir"

Any chance of a piccy

[wheeljack888]

At least 1mm difference. I'll get my vernier out and post a piccie after work.

Thanks

[ribol]

There are three reasons why that can happen.

The main one on an older car is that whilst people always replace a clutch cover and plate they rarely skim the flywheel. That means you have a perfectly flat surface on the new cover side but a bad surface on the flywheel side. That will cause the flywheel side to get off to a bad start and wear out more.
The second cause is despite the fact that nobody in the world does this, some people rest their foot on the clutch pedal whilst driving. Bad news for clutch wear.
The final one is that the plate is not free to slide on the first motion shaft properly, s—t or rust on splines etc. Hope this helps.

Ivan

[wheeljack888]

Sounds about right, probably is foot on clutch pedal or crap on driveshaft causing plate chatter. Could also be the difference in friction coefficient (material and/or machining finish) or alignment of the different clamping faces. Anyway new one goes on this coming weekend!

Thanks for your comments.

[ribol]

Drive plate chatter is normally caused by the springs rattling around because they are either tired or like on some old GM cars put in there loose for a reason.
The linings on both sides will be the same otherwise the plate would judder whenever you gave it any excuse to.
There cannot be any misalignment of the clamping faces that will cause wear on one side, that will only cause judder.

Will we be replacing the spigot bearing and skimming the flywheel and doing a proper job

Ivan

[wheeljack888]

Yes, I'll be replacing the bearing and arm as well. Through work I've got access to a CMM and so can do a flatness & parallel check on the flywheel (also machining if necessary)