Pressure Plate Help

#1

I am curious to know if anyone has had problems concerning pressure plates breaking? I have had the car for over four years, and a year ago after the original transmission (shift fork) broke I have been having pressure plate woes. There are straps in three locations on the pressure plate that position the friction disk. These straps are breaking… The first two were OEM (sachs) kits and the 3rd was a reinforced pressure plate from Ft. Wayne Clutches. I have tried different engines, transmissions, flywheels (refinished/balanced) all unsuccessfully.

I have been told that the only reason this could happen is bad driving style related to unmatched high RPM downshifts for engine braking. I’m not really ready to accept this yet as I don’t believe my driving style has changed so dramatically that all of a sudden I blow up pressure plates in twenty minutes on track. I drove this car as I built it through DE’s and into racing for three years without a problem. I also haven’t been doing standing starts but do heal/toe downshift matching revs as best I can.

I am fishing for any alternative theories of what could be causing this problem or trying to see if anyone else has run into it. Eliminating everything I have changed out of the equation leaves the hydraulic system (master / slave) cylinders as just about the only things left. Thanks in advance for any ideas or help.

#2

Do you have a clutch stop to limit over travel of the pedal?

#3

Kelly - This must be an agonizing experience. Scott Ferguson had a similar failure of the pressure plate at VIR earlier this year, however his was an original clutch with xxx,xxx miles and at least a year of race events.

I know you have done the usual stuff - replaced the clutch disk, pressure plate, release bearing as a set. It almost sounds like an alignment issue, but if you have replaced the transmission and engine, then that is minimized as a culprit. Mike and I beat on our cars, over 2 seasons, and although we have had one clutch disk issue, no pressure plate problems. Maybe your thoughts on a clutch slave issue are worth fleshing out. Another thought is the lever arm that acutates the release bearing. Again, just trying to help with potential culprits. Best of luck in sorting this out.
Ed

#4

Kelly, I feel your pain. I went through the exact same thing a couple years ago. I broke 2 pressure plates in very short order and had to pack up early on several race weekends. Based on what worked for me, I’d recommend two things:

  1. Call Rob @ Bimmerworld, tell him what’s going on, and have him order you an extra beefy pressure plate/clutch from Clutchmasters. They can custom make a pressure plate with extra strapping in those areas that are failing. If memory, serves they made mine with 5 metal straps versus the usual 3.

  2. Unless you can guarantee that it’s good, replace your slave cylinder. When I replaced the clutch with the Clutchmasters one, the slave cylinder was found to be leaking and I think that was at least contributing to the problem. (Clutch wasn’t fully disengaging between shifts. Do you notice upshifts are slightly harder than usual?)

The Clutchmasters stuff won’t be cheap (I think ~$600 or so, you have to buy the clutch disc and pp together) but it’s worth it to have this frustrating problem over and done with. I’ve had zero problems with mine since.

BTW, everyone told me the same thing – that my driving style must be too rough on the car. Like you, I didn’t buy it because I had been driving on the track for years and while I’m not perfect I had been relatively easy on equipment, was heel/toe’ing since way back, etc. Apparently, these pressure plate straps are a weak point that often break on higher horsepower cars (E36 M3, etc.) but it’s somewhat rare to have them fail on E30s.

Hope this helps,
-Joe

#5

Thanks for the info… we tried one reinforced pressure plate but we are swapping the slave cylinder tomorrow to see if it is contributing to the problem. I’m crossing my fingers. Thanks for the info!!!

#6

Well the slave cylinder didn’t help… but I got some interesting video of the last one coming apart. The stranger thing is it happens when I push the clutch in (not out) during an upshift from 3rd to 4th gear. The video is uploaded at: http://www.youtube.com/watch?v=9yrzE03Q0qw

I’m looking for any theories as to the cause… Thanks,

#7

kchildre wrote:

I would venture to say the opposite; proper fast up shifts (called speed shifting in drag racing) could be causing strain on the pressure plate. Speed shifting is usually defined as shifting before RPM’s fall to match the next higher gear via fast shifts or riding the rev limiter between shifts. My point, maybe your up shifts are harder and faster than the average person’s.

#8

Cory1970 wrote:

[quote]
My point, maybe your up shifts are harder and faster than the average person’s.[/quote]

You must not have seen any video of Kelly’s starts…:laugh:

#9

I have heard that a broken crank can cause problems like this, a slight crack will unbalance it and could be the issue.

#10

Drive shaft still balanced properly?

#11

Sounds similar. Results may shed some light?