Clutch Wear

So...

[TLDR version: $450 car needs a clutch...I want to use a good, used clutch disk with my old pressure plate...I know I'm nuts...how nuts am I?]

I'm just going to sort of ramble and type-think out loud here.

I've never "worn out" a clutch, though I have procured and seen/driven cars that had slipping and worn out clutches.

In general, I assume that it is primarily the friction material on the disc that wears, making the disc thinner. Then when the pressure plate tries to clamp, there's not enough disc where there should be disc, and you get slippage. Right?

With this in mind, I figure I don't need to replace the pressure plate on the '85 325e I just bought...I could get away with just replacing the clutch disc.

UNLESS...unless it's fairly common for pressure plates wear out, which I assume would imply that the spring steel has lost its spring. I don't think this is a typical failure mode...but I'm sort of throwing it out there to see if anyone has experienced it.

Yes...optimally, I'd replace the whole package (clutch, pressure plate, throwout bearing...and likely several other things).

Yes...I'm aware of the consequences (doing a clutch job TWICE).

I'm just not sure how to quantify the risk are using an old pressure plate with a good disk. I think the odds are in my favor...but wanted to run in past folks who think it's a good idea to throw a bunch of cheap, used parts into/at a car and then take it to Florida to compete .

Clem

think of the pressure plate and flywheel like your brake rotor, and the clutch disc as your brake pads.

they will wear into one another, and sometimes the pads will make grooves in the rotor, which will require turning to make the rotor surface smooth again for the new pads.

if you pull it all apart, and the flywheel and pressure plate surfaces are smooth, you could possibly get away with just a roughing of the surfaces and a new disc. if the clutch has been slipping, this will not likely be the case, as the rivets that hold the friction material to the disc usually cut grooves into the pressure plate and flywheel. also, if there has been any significant slipping, the flywheel and PP could have also been burnt/discolored/warped.

if you have all the time in the world to go back in and re-do the work, then go ahead and try just doing the disc, but for the amount of effort required, its usually cheaper to do it once and replace everything than to take it apart twice to replace things that should have been replaced the first time in.

Strizzo is right. But if you really want to just replace the disc, look at the pressure plate for heat discoloration--aside from the obvious grooves from the rivets. If it's multi-colored, just replace it. Also, check the throwout bearing for runout and if it sounds "gravely" when you spin it.

Your time and money. And since this is not your daily driver, try a used clutch disc. Personally, I think it's an exercise in unbolt, bolt, unbolt, install new clutch, bolt.

triumph5 wrote: ...And since this is not your daily driver, try a used clutch disc...

Oh no...it will be my daily driver.

I'm not afraid of a couple of little grooves...but yes, if I get in there and it looks bad, I'll replace stuff as necessary.

You know how it is...we cheat the system sometimes because we can. Yes...it's best to replace all the typical components...but if I can take a look and be relatively sure all the parts are ok...I'm fine with it.

Heck...I could drive it indefinitely with the slipping clutch...but that's no fun.

Mostly, I want to be the guy who's got $600 into a running, driving E30. The car only has to last through the next year or so...but I have a feeling it'll last longer.

Really...I'm not looking for advice on whether to do this or not, but just discussion about clutch failure modes.

So...it's been a long time but I did have a pressure plate fail on me one time. It was in an old '65 Chevy truck with a 3 speed behind a small block chevy.

I went to push on the clutch. It gave some resistance, so I pushed harder and something broke and the pedal went to the floor. I got to drive home sans clutch disengagement.

I don't recall the exact failure mode, but it was definitely the pressure plate.

So that's not a case of a pressure plate "wearing" out...but it did break.

Clem

i've seen them come back to autozone after the pressure plate cracked in half... i'm sure that made a helluva racket.

They will ultimately fail to grab all together. I mean, shift into gear, let up on the pedal, rev engine, and move no place. Zip, zilch. No moevement.

Bite the bullet, buy a clutch kit, get it over with. I have a feeling you'll have other areas body where you can cut corners. And since this IS your daily-get-to-work-so- you-can-get-paid-car, that places the clutche's reliability factor a lot higher on the list of "this must work right."

The other thing is that the Pressure plate can fail to disengage. THEN YOU CAN'T GET IT TO DISENGAGE the pressure plate.

This happened to my Mitsubishi Mighty Max. I could drive it, but had to shut if off at a light/stop sign. Slip it into first, then turn it over with the starter, engine woujld catch, and I'd drive it by quickly upshifting, and matching revs on the down shift. The clutch plate fingers had been eaten by the throwout bearing.

Also look for broken/rusted pressure plate springs, aforementioned plate finger wear--you'll seee a circular groove cut by the throwout bearing. And check the clutch fork for excessive sloppiness. If that fails. see above about fail to disengage.

Good luck with the project. I applaud your direction, just think agree to disagree with your priorities on it.

Looks to me like you can get an OE (Sachs) clutch kit (disc, pressure plate, TO bearing) for less than $250. Unless you value your time in pocket change/hour, I don't see how used makes sense here.

I think this is one where the journey is AS important as the destination.

Ask yourself this. Do i want to do this job twice? If answer is its not that bad to do then toss a disk at it and go but if its one of those PIA jobs save your time and $$ and buy a clutch KIT with disk, plate, and bearings.

44

Your comments are correct in or opening thread. And if the the pressure plate and flywheel are fine, you can indeed go with just replacing the clutch disc and be fine. No different than doing a brake job by installing new pads and nothing more.

But you don't know how the pressure plate is until you get inside and look at it.

So don't buy parts until you take the transmission out. Then decide.

And, depending on how horrible the transmission removal job was, that will likely steer your thinking some. For some transmissions are easy to drop, some are a nightmare. I've no idea where this BMW transmission falls.

This is more of a VW specific problem, but pressure plate failure can get ugly. This nearly new pressure plate failed while out on track at Spring Mountain Ranch. The first picture shows a little of the damage that happened inside the bell housing. The second picture is of the pressure plate after it disassembled itself while at speed. In other words, slipping might not be your only problem with a used plate.

foxtrapper wrote: Your comments are correct in or opening thread. And if the the pressure plate and flywheel are fine, you can indeed go with just replacing the clutch disc and be fine. No different than doing a brake job by installing new pads and nothing more. But you don't know how the pressure plate is until you get inside and look at it. So don't buy parts until you take the transmission out. Then decide. And, depending on how horrible the transmission removal job was, that will likely steer your thinking some. For some transmissions are easy to drop, some are a nightmare. I've no idea where this BMW transmission falls.

This is the right answer.

I've replaced the disc only, many times.

I say used parts

Cone_Junky wrote: This is more of a VW specific problem, but pressure plate failure can get ugly. This nearly new pressure plate failed while out on track at Spring Mountain Ranch. The first picture shows a little of the damage that happened inside the bell housing. The second picture is of the pressure plate after it disassembled itself while at speed. In other words, slipping might not be your only problem with a used plate.

If anything...this proves that a new pressure plate is suspect and one should only go with known good, stress tested parts.

Yes...I'm joking...but still, you have to admit that that is the point that is made.

So...I've not made up my mind about this...and as I've stated before, I'm FULLY aware of the consequences if I were to decide to just stick in a disc and my decision ends up being wrong.

Options at this point are:
Used clutch disc and pressure plate.
New clutch disc, pressure plate, throwout bearing, and pilot bearing.
Used clutch disc only (with old pp).
New clutch disc only (with old pp).

In this situation, saying "It's only $250" seems a bit out of place. I don't want to make the discussion about my particular situation...but as it is, it's a $450 car. When running right...the car will probably not be worth but maybe $1,000. So...I don't need to throw hundreds of dollars at it.

Now...that said, if I could use a new clutch on another E30 car later (and I think I can), then it would influence my decision a bit. Same with shocks and struts and such.

I would actually go with used also. I think the e30 and VW transmissions are so easy to pull out it's a non-factor. Labor is free, but new parts are not. I would gamble with a few extra hours of labor anyday.

fwiw i think e30 transmissions are pretty easy. i forget if you have to drop the exhaust, but i think it makes it easier, sometimes depends on the model. the two 'trickiest' parts are putting the starter nuts/bolts back in if it isnt a newish threaded starter and disconnecting the clip to remove the shift carrier, though thats easy once you get the trick. the bellhousing bolts are probably mostly inverted torx, and you ought to drop the driveshaft center support to pull it off the output flange. just mark the location as it ought to be preloaded forward a small degree.

i'd run a good used clutch as long as the old stuff wasnt all warped or badly hot spotted. i'd get a new throw out bearing though as its cheap enough to warrant not having to do the labor again.

The throwout bearing should be easy to obtain locally (I need to check that out) and I can have one on hand. If there is ANY hint that it's bad, I'll throw a new one in (assuming I use used parts for the clutch/pp).

I definitely agree it's cheap insurance against extra labor.

Clem