ZF Transmission: Clutch pedal stiffness causes?

[I*Do*Werke]

So there has been a lot of discussion about the "correct" combination of master, slave, clutch disc, pressure plate, and throw out bearing with the zf trans. As with many threads on this forum, a lot of the information is incorrect. Im looking for a definitive answer on the right way to do this.

Here is my personal experience and setup:

- 1991 airbag 325is originally automatic. Swapped in an M52 and ZF transmission from a 1996 328is
- The airbag e30s have a strange pedal box in that it is welded to the steering column. Couldnt use a manual pedal box so I just swapped the plastic clutch pedal and brake pedal over from a manual e30. Because I have the automatic pedal box, there is no place for the helper spring. I have a clutch stop as well
- When I first did the engine and manual trans swap: I used a Sachs e30 325is master cylinder, hard clutch line, Febi e36 328i slave cylinder, ebay e36 328i single mass flywheel and "stage 2" clutch/pressure plate, new e36 328i TO bearing and pilot bearing. Everything was bled properly.
- With the above setup, the clutch pedal felt very very stiff, more stiff than a stock e30, and much more stiff than an e36
- 700 miles after the swap, the e30 master cylinder seal blew out. I assumed it was a defective part and got it replaced with another Sachs master cylinder.
- 800 miles after I replaced the master cylinder, it blew out again. Fvck that.
- next time I bought a cheaper, Uro parts brand master cylinder. I noticed quite the difference between the Sachs and Uro master cylinder. The Uro MC looked stronger and the piston had more travel length than the Sachs MC.
- I figured out why the previous 2 Sachs MC's blew out; the piston travel was much too short and the added force needed to disengage the clutch put extra wear on the seals and ultimately blew them out.
- Fast forward ~7,000 miles and the Uro MC is still doing fine although the pedal is still extremely heavy. I have gotten used to the pedal feel so it never bothered me until last weekend when the fvcking clutch pedal snapped in half.

Seriously, the plastic clutch pedal snapped in half with an explosion rivaling that of an M-80 firecracker. It was so loud it actually scared me.

Anyway, I decided that enough was enough. I ordered a new clutch pedal (which was impossible to find) and searched through r3v to see what others had to say. Ignoring simple problems like bleeding properly and kinks in the hard line, what could be the other causes for a stiff pedal?

My main thoughts:
1. It has to be the e30 master, if you are using the complete e36 driveline, it would make sense to also use the e36 MC. I have measured the bolts and the e30 and e36 master cylinders have the same bolt spacing so I know that the e36 master will fit. Most likely I will end up buying an e36 master and using that
2. Maybe the heavy clutch is an unavoidable side affect of putting the e36 driveline into the e30. The e36 clutch pedal has a much better leverage point on the master than the e30 clutch pedal and thus makes me think the e30 pedal was never made to support such an extra load.
3. I have heard many other people's inputs but they seem to address the problem of high/low clutch pedal friction point rather than stiffness. My clutch pedal has a normal friction point, but an abnormal stiffness.

Please, lets keep this discussion intellectual and informative. I would love to hear your personal experiences and knowledge. Also, anyone who knows for a FACT the correct way to address this issue will receive adoration and respect from all e30 swappers across America.

Thanks in advance :up:

[328ijunkie]

'stage 2' ebay clutch/pp setup has alot to do with it, and the rest you can try throwing an M3 slave in there which has a larger bore iirc.

[I*Do*Werke]

'stage 2' ebay clutch/pp setup has alot to do with it, and the rest you can try throwing an M3 slave in there which has a larger bore iirc.

my friends e30 with 'stage 4' clutch/pp feels about the same as mine. its weird how stiff my clutch is. Ive had experienced bmw guys tell me that my clutch is the stiffest they have ever felt

[328ijunkie]

grease the tob guide tube?

[Voluted]

My buddy with a 99 328i has the same ebay stage 2 flywheel/clutch kit in his car and his pedal is very stiff too. Maybe it's just the pressure plate they use in that kit.

[Wanganstyle]

problem:

EBAY (f1 criptforce) Pressure plate. There is one of those locally that is blowing the slaves.

some relation of flywheel and pressure plate and friction disc is WRONG

My e30 has a sachs master in it, and sachs slave for ZF320. It is paired with a BMW OEM 2009 335i twin turbo clutch and the genuine hydrolics been taking the genuine BMW twin turbo clutch for a while. No such weird issues with S52 dual mass+ s52 genuine clutch in M20 with g260 either.

6 months of dd/street/1 track day/ 1 drift day. happy hydrolics

[DTFE30]

Does anybody know the difference in displacement between the E30 master cyl and the e36?

[nando]

- The airbag e30s have a strange pedal box in that it is welded to the steering column. Couldnt use a manual pedal box so I just swapped the plastic clutch pedal and brake pedal over from a manual e30. Because I have the automatic pedal box, there is no place for the helper spring. I have a clutch stop as well

that's because late cars don't have the "helper spring". the part # for airbag manual and auto pedal boxes are the same - the only difference are the pedals.

it's not welded to the steering column either, but it's more difficult to change the pedal box than just the pedals.

also, those plastic pedals are shit. you can get metal ones - I got mine from a 318is, but I have no idea which cars came with plastic and which came with metal.

a "stage 2" pressure plate (whatever that means) is probably significantly stiffer than a stock one, which also contributes to your pedal stiffness.

[I*Do*Werke]

My buddy with a 99 328i has the same ebay stage 2 flywheel/clutch kit in his car and his pedal is very stiff too. Maybe it's just the pressure plate they use in that kit.

problem:

EBAY (f1 criptforce) Pressure plate. There is one of those locally that is blowing the slaves.

some relation of flywheel and pressure plate and friction disc is WRONG

That would make sense, but the pressure plate that came with my ebay kit was actually a Sachs sport PP. The clutch disc and flywheel were not, however.

Edit: I just checked with the ebay seller (gripforce/f1 racing), the pressure plates used in all of their Bmw kits are indeed sachs heavy duty pressure plates

Does anybody know the difference in displacement between the E30 master cyl and the e36?

This. I would like to know

[nando]

the 618pp is pretty stiff. it sounds like it could even be normal.

[I*Do*Werke]

the 618pp is pretty stiff. it sounds like it could even be normal.

Normal enough to blow out 2 master cylinders and snap a clutch pedal in half?

[nando]

the plastic ones? sure. I'd hate to have one of those.

the MCs - I have no idea. I know for sure my clutch is much stiffer than any other car I've driven. the "HD" pressure plates have about 50% more clamping force than the stock pp. you'd expect there to be a 50% increase in effort. my wife won't drive my car. :p

not to say you don't have a real problem or it couldn't be made better - just saying, a significant amount is definitely being caused by the HD pressure plate.

[328ijunkie]

Assuming your mc isn't overtraveling then yeah. You have to think of it. The master does all the 'work' the slave is similar to a caliper piston for your brakes. It just distributes
The work from the master. <lol

Throw a normal clutch setup in there and it'll
Change everything

[I*Do*Werke]

Is there a master cylinder that would lessen the required force to disengage the clutch? e36 master cylinder? maybe a ///Master cylinder?

[Wanganstyle]

e34 clutch master cylinder. or the metal threaded e36 unit, they eyeball side to side as compatible

I have a e30 stock master cylinder in my car and it has paired happily with ZF sg320 e36 M slave and the e46 zf sg320 slave also.

is your master cylinder dead?