Hey guys, check my logic here. I see this type of grooving all the time, on nearly every pressure plate I see - regardless of engine type, horsepower, etc. I hadn't given it too much thought other than, "I don't like it, but it happens every time." But I was just talking with someone and it occurred to me that this might be wear caused by a bad throwout bearing. If the grease is sticky, or if dirt has infiltrated the bearing, it may not be able to rotate/spin correctly and would slip causing wear.

The point of the throwout bearing should be to stop exactly this type of wear, right?
Doest this mean bad throwout bearings are super common?
Or is this a symptom of a loose clutch cable, not holding the throwout bearing tight to the fingers and that lets them slip?

How many miles are on that PP? What type of driving? Mine is in the same (worse)shape and I was also wondering this same question...

I always understood this was the opposite of a loose cable. I thought ideally your throw out should hover just out of contact with the pressure plate fingers to avoid premature wear to both the bearing and the pressure plate springs, but since many cars have their clutch cable too tight, you get this.

That looks pretty bad

I see two forces happening here. One is rotational. If the bearing is stiff (or frozen) then there will be some slippage maybe only at first contact. The worse the bearing the worse the amount of slipping. The other force is the bearing being pressed toward the engine. Even with the throwout bearing operating properly there will be some sliding of the bearing moving in and out on the fingers. This will cause some wear. I don't think there is any getting around that.

Looks like a real lot shifting, a too tight cable, or a bad release bearing. Not sure what any manual says, but I've always put a very light coat of grease on those fingers.

It happens to all pressure plates, regardless of car make or year.
The sun should outlive the plate itself. No point in investing efforts here.

This is one reason I have been taught in the past (I'm talkin' long ago) that the only time you should dis-engage the clutch is when sifting gears. When I come to a stop light etc. I shift the trans into neutral rather than sitting with the engine idling with the clutch dis-engaged. I used to have a 1960 VW bug (I'm talkin' long ago) and instead of a throw out bearing it used a block of graphite that rubbed against the PP to dis-engage the clutch. When the graphite wore down, the metal cup it was housed in would grind a groove in the pressure plate. The less time you held the clutch pedal down, the longer the graphite block would last.

I have learned this as well. Always go into neutral, never hold the clutch down at a stop. Probably easier on the clutch cable tube as well. But wouldn't a properly adjusted clutch just narrowly disengage the throwout bearing in neutral. So when the clutch is depressed every time, the bearing has to make contact with those fingers which are rotating and the bearing is not. Friction would occur at every gear change.

John

356 Pressure Plate of unknown age.
Click to view attachment

914 Pressure Plate of unknown age.
Click to view attachment

Do you have photos of the throwout bearing?
What does the bearing surface look like?

I have been reading quite a bit about this lately because the Mini needs all of this replaced and the PP looks worse than the first one you posted.

It's interesting, but it seems to be a more modern car issues because I never had any issues with big old american iron.

The resurgence of the blame being shifted to the driver is a poor excuse for building an inferior product, the throw out bearing or release bearing.

The crappy manufacturing has taken out a pressure plate, throw out bearing and left the clutch with less than 30 k miles on it....

This is just cheap parts in cheap cars nowadays.

Rich

Not on a 914, at the very least! Remember, the 914 has a spring on the pedal cluster that pulls the pedal down in the "press the pedal" direction. That means there is always pressure on the throwout bearing--though not a lot.

This kind of wear is exceedingly common--maybe universal? I don't know why, because it seems to me that the T/O bearing should be there to prevent that. Especially if the bearing is always in contact with the fingers on the plate, so it should not have a chance to slip.

Maybe it would be worse without a real bearing in place?




The top of the bearing has a rounded surface. Basically it's just the inverse of the wear that you see in the pressure plate fingers in the pics above.

Here's a pic:



--DD

Slight contact between the throwout bearing and pressure plate with not a lot of pressure would allow the pressure plate to turn faster than the bearing at times which would cause the wear. Like at a stop light in neutral punching the gas pedal - zoom zoom. Also as the bearing wears it would be less responsive to quick starts, again causing the wear on the PP.

I understand that the pedal is pulled down by a spring which would cause the throwout bearing to always have some kind of contact. I was under the impression that you do not want the throwout bearing to always be spinning which would cause it to wear out faster. Isn't that why we are told to not rest our foot on the clutch pedal while in neutral?

So my question, the PP picture in the first post, is it usable?
I ask because I'm the one that sent it to McMark wondering if I should use it for my 3.2 or buy a new one. It's a kep stage II.

I just changed my fifty plus year old original pressure plate in my MGA...the fingers were worn but not grooved. My guess is bad TO bearing.

The bearing in the A was definitely worn but spun freely...the face was worn in a matching pattern. The bearing should ride gently against the surface as pressure dictates...nothing more.

here is a good start for further investigation: see pages 4 & 5

clutch diagnosis

Aha!

Now i'm curious as well, but i see a clear pattern here.
Since my transmission always has had trouble getting into gear when at a standstill, i *always* keep it in gear and my foot on the clutch when stopped.

Interestingly enough, i never noticed any grinding noises ...

Doing as you do, Andy, is a guaranteed way to shorten the life of the thrust bearing in the crankcase. T1s and T4s are known for this (takes out the case, too), as are 4 cylinder VW watercooled engines. I've also seen it in Toyotas, Hondas, and even Hyundais. It CAN happen to you ...

The Cap'n

From what I could tell once it started to get loud, it was challenging to get into gear, but not everytime.
There was more than enough push to free up the clutch, most of the time.
Mine, on the mini, was worn down more than hallways through the spring teeth.

The issue we had was noise and hard shifting...never any clutch slippage.
To the OP , considering how hard it is to replace, you may want to do it now.....or just run it until it won't shift...then do it.

No, i guess i should have been more clear.


- The pressure plate in question is from my car, it's my old KEP Stage 2.

- Not being able to get in gear is a problem with my transmission internals and has nothing to do with the clutch setup. I've had this transmission for 12 years and it's always been like that.

- I simply commented above that i never heard any grinding noise when stopped. Judging from the amount of wear, you'd think there would have been some noise.

- Now i wonder what my current PP looks like. I went with a KEP Stage 3 setup a while ago.

Got it....
Again, it's a risk, but if it's free or super cheap, and you are ok replacing it eventually, go for it....but know it's an issue that will need to be fixed...soon.

I have yet to receive the beer i asked for it ...

That's only because I haven't seen you yet!!

Come by the shop.....all the beer you can

How soon....are we talking 5000miles, 50,000 miles.

If the tip of the fingers break off, what happens, anyone see that?

Thanks
Jeff

I don't think so. There's also a much larger spring on the transmission's clutch arm that pulls it back, disengaging. You need free play at the top of your clutch pedal, meaning no contact between the release bearing and the pressure plate until you press the pedal past the free play. I think those grooves are created from the friction of the "spin up" of the stationary release bearing as it matches speed after contacting the spinning pressure plate. When the grooves are deep that metal's gone and not coming back, so it's time for a new pressure plate.

When you sit at a stop light with the clutch disengaged you're wearing the throw out bearing, but much worse is that you're causing unneeded wear on the engine's thrust bearing. It's what limits the front-back movement of the crankshaft, and every time you press the clutch the pressure opens the pressure plate, but it also presses the flywheel and crankshaft forward, against the thrust bearing. And it's a heck of a lot more expensive to replace a main bearing set than a throw out bearing. You check how many miles are on the bug's T1 engine by pulling and pushing the crank pulley? Any movement is end-play from a worn thrust bearing, meaning a lot of miles on the engine (or a lot of time at stoplights with the clutch in) and an impending engine rebuild.

What transmission do you have? Because you're not describing a 901-based 914 transmission here--there is no spring on the throwout arm at all. Maybe the 915 version out of the mid-year 911s...

--DD

Ahhchh.... you're right, Dave, that spring is on a VW transmission, not a 901. The principle's the same, though.

Wow, What a dumb design. glad i read this. Another thing to modify as I slowly get this crate together. Neat little car, but lots of room for improvement no doubt.

Google images shows some of these with broken fingers, so it does happen. Worst case scenario you lose some or all of your ability to disengage the clutch. Then you get it home, pull the transmission with the engine still in place, and swap in a new pressure plate. If it were my personal car, I'd run it and plan on swapping it out in a year or so.

It's not just this car, it's every older car. Those clutches work fine for decades... just not forever. I've never seen a failure because of wear on the clutch fingers, the rest of the clutch is toast first.

Actually now that I think about it maybe I have, but it's not common.

Fingers broke on my son's Kennedy pressure plate just recently, but we think from a cracked diaphragm, not from common wear. If it fails it will make noises, won't disengage, and you'll know it ahead of time.

A lot of the comments seem to point to the throwout bearing spinning on the fingers. While this would cause wear, it may not be the problem at all. Each time you press on the clutch, the throwout bearing pushes in on the fingers even with the throwout bearing and the pressure plate spinning together (no circumferential slipping). Here the bearing must slide metal on metal without lubrication. This is going to cause wear. Grease would help but who wants grease so near the clutch. Harder bearing and softer fingers means the fingers will wear first.

I was referring to the clutch release bearing having slight contact all the time. I don't like that. nothing wrong with the clutch itself. Sachs makes good stuff.

Thanks, appreciate the input, I guess I'll plan on using it so I can get my car back on the road. Then I'll just have to start saving up for a new one, maybe change it next winter......if it makes it that long my throw out bearing is fairy new, so that may help....and no riding the clutch pedal.

Most clutches that I've replaced have looked like that at the end of their life.
I replaced one in the Saab I drive that had lost about a third of the fingers at the end. The big problem in that clutch though was that the driven plate came to pieces.
Worth looking at newer cars and how they run their concentric slave cylinders now. The bearing is designed to be in constant contact with the pressure plate. Throw-out bearings are typically a high clearance design and engine speed is hardly going to worry a bearing designed for 15krpm max. What kills bearings inside their design range is shock and pressure. The shock of a bearing coming from nothing to engine speed every time you touch the clutch will wear it faster than it resting lightly against the pressure plate all the time.
I really need to find the time to finish my concentric slave to replace the pull type I'm using now.