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Sun May 31, 2020 7:01 am

whats the purpose for shimming the pressure plate? i was scrolling through the classifieds and saw a Gene Berg pressure plate shim kit that says its for use with short rivet but not long rivet p.p. , or maybe it was the other way around?

Sun May 31, 2020 7:54 am

You shim the pressure plate out to get best grip on the clutch disc.

My Stage I PP and CB Super disc held to 165 lb. ft. of torque.
My Stage II PP and Daiken 503B disc held to 175 lb. ft. of torque and still slipped in the buggy.
Of course I found out after I installed it since I "assumed" it would hold more due to being Stage II.

Once I pulled it all apart again I tested the old and then the new and found only a gain of 10 lb. ft.
I then shimmed it using the VW style wavy washers which happen to measure out at .031 inch. That gave me a gain to 250 lb. ft. I couldn't test it higher due to my torque wrench maxing out at 250 ft. lbs.

I ended up reusing the CB Super Disc along with the Stage II for best holding power.

You can buy shims if you want but you still need to test it to see if you gain or loose. Each disc and/or PP might be different.

Find an old transmission input shaft and weld a socket or a nut on the flywheel end and you can use a torque wrench to test it.
I use a flywheel lock to keep the engine from turning.

Sun May 31, 2020 8:14 am

I just posted this recently if you search through my post history. Thomas Simpson made a video explaining how to dyno a clutch so you get maximum gripping force when the clutch is engaged. Shimming also prevents the fingers from over-traveling to disengage, which causes the springs to fatigue faster. I stocked up on round shims in various thicknesses so I can do all my clutches and my customer's clutches too.

Sun May 31, 2020 9:08 am

great info, thanks. i can understand measing and adjusting for variations in disk thickness but aside from disk thickness i guess im not grasping the concept quite right.. wouldn't shimming the p.p. farther from the disk & flywheel give less clamping force?

Sun May 31, 2020 9:15 am

https://www.thesamba.com/vw/forum/viewtopic.php?t=730313&highlight=clutch

Sun May 31, 2020 10:46 am

The fingers have to be parallel, more or less when engaged. Some thick clutches have the fingers past parallel. Get it?

Sun May 31, 2020 11:27 am

Is this more an issue with disc thickness variations or pressure plate variations? Without a press/setup as Tom showed in the video, it seems shimming by trial and error and measuring torque to slip nunbers is how it is adjusted for optimum?

Sun May 31, 2020 6:22 pm

How is shimming effecting the balance of the pressure plate. My understanding is that pressure plate centering is critical to maintaining balance. How can you get it centered properly with a stack of washers where it should mate up?

Sun May 31, 2020 7:07 pm

A shim under each bolt is not going to effect the balance. If you are that concerned weigh the shims......

The shims adjust the angle of a diaphram clutch. There is an optimum angle for best clamping force. You can buy a fancy gauge and test it in a press...or you can get a cheap torque wrench and test the torque resistance by trying different shims.
6-8 eight millimeter wavy washers and a 250 ft. lb. torque wrench is more than likely in most VW peeps tool box....if it isn't......it should be.
The trans input shaft might be a little more challenging to find. I got mine from a VW/Import/Tractor repair shop that retired after 40 plus yrs of service. I just welded a 15/16ths size nut on the end of it to make it more than a clutch disc centering tool. Some people just weld a half inch drive socket to the end.

The only people concerned with testing a clutch would be someone putting out some serious hp.
A Stage I Kennedy is good for 180 ft. lbs torque....Mine actually held 201 ft lbs. torque to the wheels.

It takes a very healthy Stroker to get to 180 ft lbs. torque...at the flywheel.

Once you hit 200 ft lbs torque....you need to test your clutch.

Mon Jun 01, 2020 4:31 am

clonebug wrote: A shim under each bolt is not going to effect the balance. If you are that concerned weigh the shims......

I am not talking about the weight difference in the washers, that is didly-squat! I am talking about centering the pressure plate on the flywheel. The radial runout. Did you set up a dial indicator and adjust it for a close to zero run out?

The guy that balanced my rotating mass spent considerable time on this and peening the edges of the pressure plate to insure it went back on the flywheel each time without run out. By shimming the pressure plate away from the flywheel and the register groove it is supposed to sit in, what now locates it in the center? The bolt holes are not accurate enough to do this.

Mon Jun 01, 2020 8:23 am

If you have the tall rivets in needs to go in, short rivets need shims. They arent very thick and may not have an effect on centering. Needs to be checked before balancing so it can be peened with shims in place. Berg also makes a tool to measure the pressure plate. Height of the fingers. https://www.thesamba.com/vw/classifieds/detail.php?id=2373244

Tue Jun 02, 2020 7:15 am

shimming all depends on the disk thickness.. and what the pressure plate wants for compression for maximum clamping.

Most folks don't realize that installing a disk that is too thick actually diminishes clamping force. pressure plates have a range of compression where they develop full clamping force (usually around .050" range). Outside of that range, the clamping force drops off dramatically.

And, most disks are too thick as sold.
Anything more than .300" thick is giving up clamping force unless you shim it.

Folks throw things together and then say these parts suck when they have no idea if the clutch is in the "happy zone" or not.

A good rule of thumb is: For a Kennedy pressure plate, choose a disk in the .240"-.290" range and it will work as it should.
Anything thicker needs shimmed.....

Tue Jun 02, 2020 9:13 am

Hi, new here but appreciative of some great info. Trying to understand the shimming with these Kennedy pressure plates and Daiken discs.

I understand the Kennedy plates were until recently made with the short rivet which you can shim with a berg kit for example. I just received a new stage 1 and it has the taller rivet which berg say you can't shim.

I'm going on some old info that says cone height should be 29-30mm from flywheel to top of the plate cone. I'm guessing this is what the berg tool measures..29-30mm ?

With the old stage one (short rivet) I could use the berg shim kit and be right on 30mm with a Daiken super disc (approx 8mm thick,)

New tall rivet Kennedy is 28mm without shims but 32mm with so (same Daiken) I guess I need thinner shims. Is this a problem ? I'm not sure why berg say you can't shim the new plates...unless the rivets will hit the trans case as suggested ?

I'm not after crazy clamping force, just a nice feel/engagement to the clutch with a good life to it and no judder etc

How do other new discs compare in thickness ? Centerforce/dual friction that type ?

Tue Jun 02, 2020 2:36 pm

Ohio Tom wrote: shimming all depends on the disk thickness.. and what the pressure plate wants for compression for maximum clamping.

Most folks don't realize that installing a disk that is too thick actually diminishes clamping force. pressure plates have a range of compression where they develop full clamping force (usually around .050" range). Outside of that range, the clamping force drops off dramatically.

And, most disks are too thick as sold.
Anything more than .300" thick is giving up clamping force unless you shim it.

Folks throw things together and then say these parts suck when they have no idea if the clutch is in the "happy zone" or not.

A good rule of thumb is: For a Kennedy pressure plate, choose a disk in the .240"-.290" range and it will work as it should.
Anything thicker needs shimmed.....

for some reason that all of the sudden makes sense now...

Wed Jun 03, 2020 3:38 am

jason wrote: If you have the tall rivets in needs to go in, short rivets need shims. . Berg also makes a tool to measure the pressure plate. Height of the fingers. https://www.thesamba.com/vw/classifieds/detail.php?id=2373244

Could you expand on this a bit more please. Tall rivet plate puts my height at 28mm with my disc. Should I shim it to 30mm ? Is that what the berg tool measures..29-30mm ? Thanks

Tue Jun 09, 2020 3:18 pm

Great! More tools to buy! \:D/

Sun Feb 28, 2021 8:20 pm

Bookmarking for toilet reading😉