Car is eating pressure plates what gives? E36 M3 1995

[JaredM3]

2 years ago I replaced the original clutch and flywheel with a UUC ltw flywheel that uses a M3 PP and a sprung disk.

1 year goes by on this setup 2 track days and a drag strip run. The last run at the drag strip a stap on the PP cracked around the rivet.

I replaced it with a sachs HD PP with 3 straps thick instead of 2. I put 600 miles on it all street and a strap lets go in the exact same manner.

I replace it with a stock pressure plate 200 miles in and 1 track day and on the 3rd session strap breaks in the exact same manner once again. I babied the last replacement and was perfect on my downshifts and babied the upshifts for fear it would let go once again, and it did.

-The fork, t/o bearing, and pin were replaced every time. And I know my driving is NOT a factor.

-Not a HP monster (couple bolt ons)

-Driving/heel toe/rev matching NOT A FACTOR

My finger is pointing toward the flywheel because I never had clutch problems before it went in.

[99MPower]

2 years ago I replaced the original clutch and flywheel with a UUC ltw flywheel that uses a M3 PP and a sprung disk.

1 year goes by on this setup 2 track days and a drag strip run. The last run at the drag strip a stap on the PP cracked around the rivet.

I replaced it with a sachs HD PP with 3 straps thick instead of 2. I put 600 miles on it all street and a strap lets go in the exact same manner.

I replace it with a stock pressure plate 200 miles in and 1 track day and on the 3rd session strap breaks in the exact same manner once again. I babied the last replacement and was perfect on my downshifts and babied the upshifts for fear it would let go once again, and it did.

-The fork, t/o bearing, and pin were replaced every time. And I know my driving is NOT a factor.

-Not a HP monster (couple bolt ons)

-Driving/heel toe/rev matching NOT A FACTOR

My finger is pointing toward the flywheel because I never had clutch problems before it went in.

the blue flywheel strikes again

[bennyfizzle]

oh gosh another one of 'these' threads.

[magnetic1]

The PP is a weak point in the E36. Ive gone through quite a few and it sucks when it happens in a race. You can get upgraded PP from Bimmerworld or get custom done.

[ssburns]

Fort Wayne Clutch will resurface your PP and add three straps to for much less than a new stock PP. May not fix the problem, but much cheaper than buying new stock or HD PP's.

I swapped back to a stock FW when I had the above done, so I can't say if it will 100% prevent reoccurence with the LTW FW or not.

[JaredM3]

The PP is a weak point in the E36. Ive gone through quite a few and it sucks when it happens in a race. You can get upgraded PP from Bimmerworld or get custom done.

Well its hard for me to buy the weak point when I put in a heavy duty 3 strap PP and it broke in 1500 miles of very light street driving...

I never had a problem for 3 years and 25,000, it was after I put in the flywheel and its just chewing through them.

[dbbmwm3]

I've been using the BW 6 puck ceramic clutch set up with success and no complaints. Here's the description from their website:

This BimmerWorld clutch kit is designed in cooperation to meet the needs of the road course racer. The pressure plate incorporates a ductile iron casting that has been designed with a different fulcrum point to increase leverage for increased clamping pressure while keeping pedal pressure reasonable. The straps and hardware attaching the casting are also beefed up to withstand heavy use. The clutch disc is lined with a Steel Backed (TM) friction material for better bite, improved thermal dissipation, and long life. Now, all BimmerWorld/Clutchmasters kits employ a stack of FOUR heavy-duty straps, held with up rated rivets. These added strength parts will endure extended extreme use. Clutch disc is a 6 puck ceramic design to optimize grip and durability, but retain paddock drivability. Complete kit also includes throw out bearing.

[SG_M3]

the blue flywheel strikes again

Well its hard for me to buy the weak point when I put in a heavy duty 3 strap PP and it broke in 1500 miles of very light street driving...

I never had a problem for 3 years and 25,000, it was after I put in the flywheel and its just chewing through them.

I was blowing through pressure plates in a weekend, twice we had this happen. Turned out the crankshaft was tweaked in the engine. Swapped engines, no more pressure plate problems. That engine hadn't done it before, but we suspect the vibration/harmonic finally got bad enough where the single mass flywheel couldn't control it and the pressure plates were suffering. Thank god for Clutch Masters standing behind their products, working with them on this issue was great. Can't thank Clutch Masters and BimmerWorld customer service enough.

[sstecker]

the first of 3 - straps broke and a dowel was pulled out with a 4 puck unsprung clutch/lightweight fly. no problems since switching to bimmerworld clutchmasters segmented disc and upgraded pressure plate.

[Rob Levinson]

For those citing the flywheel - let's have some common sense. He's not having vibration issues or anything else.

First question for Jared, because I didn't see it mentioned in your posts... have you removed the CDV? See:
http://www.uucmotorwerks.com/html_te...heck_valve.htm

The CDV causes excessive clutch slippage no matter how you release the clutch, and this can overheat a clutch assembly.

Second thing, which I've discussed at length in other threads, is track downshifting technique.

If you use excessive engine braking (downshifting and using the transmission to slow the car), then you are "reverse loading" the pressure plate and compressing the straps. Straps are strong in tension, fragile in compression.

Pressure plate (PP) straps generally look like this:


What you're seeing above is an overbuilt UUC PP with multiple extra-thick straps. The OE PP uses fewer and thinner straps.

In a track situation, especially with R-compound race tires, extreme engine braking and the resulting reverse-loading compresses the straps. This will either cause the strap to buckle or break, or even break the rivet holding it to the pressure plate, or simply break the pressure plate at the point of the rivet. Results look like this:



Reverse loading is the only thing that I have ever seen break a pressure plate strap in this manner, a phenomenon that my engineer friends at Sachs have confirmed in discussions about the phenomenon. We started seeing this more frequently in the early 2000s when the E46 M3s were first seeing track use... a heavier car with wider rear rubber exacerbated the problem, and early-production OE pressure plates were popping.

Obviously, this type of damage is more likely in a light-duty OE pressure plate (such as the OE M3 one that you had initially).

Take a look at the broken straps, I think you might even see they were bent before breaking... look at any on the same PP that did not break.

Hope that helps!

[JaredM3]

I understand where your coming from Rob, It is not my technique that is causing falure. I know that for a fact. Due to breaking a Heavy duty PP with light street driving in 1500 miles.

The last one that broke was being babied around the track and I was extra careful about downshifts and upshifts even...I had a bad feeling about it and it came true when I thought I missed a shift when the clutch was dragging due to a broken strap.


*all 3 have broken in the exact same manner, a slight fracture on a strap around the rivet hole.

And like I had said I never had one problem with this and I could beat the absolute crap out of it, and now with being gentle it is still lunching the PP...

[SG_M3]

http://forums.bimmerforums.com/forum....php?t=1008871

There is the thread from my similar problem.

[Rob Levinson]

http://forums.bimmerforums.com/forum....php?t=1008871

There is the thread from my similar problem.

Ah, I forgot about your bent crank issue!

Yep, that could do it. Puts the flywheel in a different plane than the clutch disk (which rides on the transmission input shaft), which then stresses the pressure plate asymmetrically. That's not a good thing at all.

And like I had said I never had one problem with this and I could beat the absolute crap out of it, and now with being gentle it is still lunching the PP...

See Sean's thread above... that might be the situation.

[JaredM3]

Well I doubt my crank is bent, I will put a dial on flywheel, crank, balancer and so fourth and check the clearances and tolerances...

I am in a BMW tech program and I have spoken to a few people and fingers seem to point to a flywheel issue...

I just honestly cant buy into a bent crank, the motor only has 30k on it and has had an easy life.

The only thing that changed was the flywheel and thats when I had pressure plate issues, it really seems like common sense (to me anyway)

[Rob Levinson]

Well I doubt my crank is bent, I will put a dial on flywheel, crank, balancer and so fourth and check the clearances and tolerances...

I am in a BMW tech program and I have spoken to a few people and fingers seem to point to a flywheel issue...

I just honestly cant buy into a bent crank, the motor only has 30k on it and has had an easy life.

The only thing that changed was the flywheel and thats when I had pressure plate issues, it really seems like common sense (to me anyway)

Let me know what you find.

I'd be surprised if it was the flywheel, but if anything is out of spec on it, I will gladly replace it and the clutch that you purchased with it.

Please call me directly at 678-679-5360.

- Rob

[ssburns]

To the OP,

Have you noticed if any of the PP bolts are loose?

I went through a similar set of failures (with a non-blue LTW FW), and noticed that the PP had backed out partially on several occasions. Went through several attemps to loctitie bolts, etc., but never quite figured out whether the bolts were root cause or sympton vs. the straps (i.e. which failed first).

Also my straps cracked on the outside of the rivets as you describe and were not bent from reverse loading as Rob's picture shows. While I can't guarantee that my driving didn't contribute, I haven't had issues with the stock flywheel, would say that if anything with the LTW FW I would grap too many revs on occasion rather than "engine braking", and have observed fellow racers who more often than not don't heel and toe at all and don't have problems.

After trashing my bell housing and destroying the third gear synchro I went back to stock flywheel with the HD pressure plate and have had no problems.

Despite Rob's comments about "common sense" it's obvious the LTW FW's in general (not neccessarily any particular brand) are a contributor to these issues as I don't know anyone who has done this with a stock FW. Sean's crank issue may explain some portion of them. There have also been some threads pointing to worn out crank dampers and high rpm operation leading to FW bolts backing out. While a seperate failure mode, I can see how that level of vibration might cause issues for the PP even if the FW bolts don't loosen.

Good luck. I look forward to another data point with some real info beyond the typical "it's the driver stupid".

Sean,

Without reading your whole thread do you know where the crankshaft was bent (i.e. at the output as Rob had commented or elsewhere)? How was it diagnosed?

[gobuffs]

Are the flywheel bolts tight? I put on a blue flywheel 4 years ago. I had the tranny out a few months ago and didn't check the flywheel bolts (figured I hadn't had an issue in 4 years, why tempt fate?)- wrong decision. Replaced it with a Clutchmasters ceramic kit from BW. No issues so far.

[Rob Levinson]

Also my straps cracked on the outside of the rivets as you describe and were not bent from reverse loading as Rob's picture shows.

Take a close look at the damaged clutch pic I posted, you can see it has the eventual outcome of a broken strap, the strap flipped around (top part of the pic) or broken out entirely (bottom part).

Despite Rob's comments about "common sense" it's obvious the LTW FW's in general (not neccessarily any particular brand) are a contributor to these issues as I don't know anyone who has done this with a stock FW.

As I posted above, the first instances of this that we saw were with 100% stock flywheel/clutch assemblies on E46 M3s.

- Rob

[SG_M3]

Sean,

Without reading your whole thread do you know where the crankshaft was bent (i.e. at the output as Rob had commented or elsewhere)? How was it diagnosed?

I don't know specifically, we swapped engines and the problems went away. A year later and no more pressure plate issues since the engine change.

[szed]

Just curious, for those who have broken pressure plate straps...have you guys looked into strapless designs such as the OS Giken units? Evosport is a distributor and I remember a thread a long while back with good results.

[ssburns]

Just curious, for those who have broken pressure plate straps...have you guys looked into strapless designs such as the OS Giken units? Evosport is a distributor and I remember a thread a long while back with good results.

Pricey and not legal for stock or prepared classes.

Take a close look at the damaged clutch pic I posted, you can see it has the eventual outcome of a broken strap, the strap flipped around (top part of the pic) or broken out entirely (bottom part).



As I posted above, the first instances of this that we saw were with 100% stock flywheel/clutch assemblies on E46 M3s.

- Rob

Mine were broken on the left side of the left rivet in the top pic (opposite of where the bending is occuring in your pic) . Radial crack from the rivet rather transverse crack from bending fatigue.

E46 M3 is an entirely differnt car. Any E36 M3's (even with sticky track tires) breaking PP's with stock flywheel? I'd tracked my car for 6 years (including a season of WW racing) with stock flywheel. First weekend with a LTW FW (not the blue one) I started experiencing issues. Struggled with it and lost several more weekends to the issue. Reinstalled stock FW, no more issues.

It's possible that the LTW FW degrades my ability to match revs, but 1) it decreases the rotational interia of the engine thereby offsetting at least some of the effect of mismatched shifts, 2) as I mentioned, if anything I would tended to grap too many revs with the LTW FW when downshifting because it takes a smaller throttle blip to get the revs needed.

[Rob Levinson]

Mine were broken on the left side of the left rivet in the top pic (opposite of where the bending is occuring in your pic) . Radial crack from the rivet rather transverse crack from bending fatigue.

Something has to give, so there are different modes of breakage depending on whose exact clutch it is. Some use stronger straps, some use stronger rivets or bolts, some use stronger or weaker plates in the cover. Weakest link goes first, so the same effect causes different damage.

E46 M3 is an entirely differnt car.

How so? An E46 chassis is virtually identical in every design with the exception of details and minor dimensional differences - everything on the E46 is very close to the E36, just about the same but with updates... suspension design, layout, weight balance, engines, brakes. In fact, the E46 M3 in Europe was a disappointment because the motor was so similar to the E36 S50B32... like all they were getting was an updated cosmetic style.

Any E36 M3's (even with sticky track tires) breaking PP's with stock flywheel?

Ayup. I've seen it myself.

Realize that track tire technology has come a long way since 1995, they are stickier than ever before. This contributes to reverse-loading.

Granted, it does happen more often in the E46 M3 due to the higher speeds and wider tires, but the E36 is not immune. Strengthen one part of the chain (stickier tires) and new weaknesses are revealed that were not evident earlier.

I'd tracked my car for 6 years (including a season of WW racing) with stock flywheel. First weekend with a LTW FW (not the blue one) I started experiencing issues. Struggled with it and lost several more weekends to the issue. Reinstalled stock FW, no more issues.

I don't know the particulars of your situation, why it would be chronic when practically all other Prepared-class racers are using lightweight flywheels without pandemic issues. Do parts break in racing? YES. You've got a racecar, you WILL break something eventually. To state the obvious, stresses are quite a bit higher in a racecar or track-use street car than the average leased 323i automatic.

It's possible that the LTW FW degrades my ability to match revs, but 1) it decreases the rotational interia of the engine thereby offsetting at least some of the effect of mismatched shifts, 2) as I mentioned, if anything I would tended to grap too many revs with the LTW FW when downshifting because it takes a smaller throttle blip to get the revs needed.

What brand flywheel and clutch were you using? I might be able to give some insight as I know how many other brands are built.

- Rob

[Moar Powr]

to the OP: Check the balance on your crankshaft.

[ssburns]

What brand flywheel and clutch were you using? I might be able to give some insight as I know how many other brands are built.

- Rob

JBR FW (earlier one I believe as the PP bolts/threads were English vs. Metric)
2 seperate PP's failed. 1st was Sachs HD PP used with a Sachs friction disk. 2nd was a Clutchnet HD PP with a Clutchnet Kevlar 6 puck friction disk.

Again usnsure if the bolts backout before or after the strap failures.

to the OP: Check the balance on your crankshaft.

How do you do this w/o tearing down the engine?

[Moar Powr]

JBR FW (earlier one I believe as the PP bolts/threads were English vs. Metric)
2 seperate PP's failed. 1st was Sachs HD PP used with a Sachs friction disk. 2nd was a Clutchnet HD PP with a Clutchnet Kevlar 6 puck friction disk.

Again usnsure if the bolts backout before or after the strap failures.



How do you do this w/o tearing down the engine?

Not sure you can, sorry.