Clutch is ridiculously stiff

[1990m3]

Can't figure out why it's so stiff, but I've never driven another car with a clutch that felt like this before. Here's my list of parts that is related to the clutch system:

- Bimmerworld LTW flywheel
- E34 M5 clutch disc
- e36 m3 stock pressure plate
- e36 m3 slave cylinder
- e30 m3 master cylinder (23mm)
- e21 brake booster
- UUC Stainless Steel clutch line

Anyone have any ideas? i've driven about 5 s50/s52 swapped cars all with the same clutch/flywheel setup and I've never experienced a clutch pedal like mine before. I have the engine/trans out right now for some body work on the car and I'd like to solve this problem before it goes back in.

Note: clutch operates very well, never slips and doesn't make any wierd noises.

Could I have been shipped the wrong pressure plate? Could the master cylinder size effect the clutch pedal effort? Could the UUC SS line really make the clutch pedal feel so overly stiff?

A few members of this board have driven the car, maybe they'll chime in too.

Thanks

Dave

[matt]

The size of the master cylinder is 100% to blame for your pedal feel.

Isnt the regular e30's clutch m/c like 20mm? Swap to that, it'll get softer.

[aeryk7]

Mine is pretty stiff but i like a stiffer pedal compared to a stock bmw feel.

[1990m3]

The size of the master cylinder is 100% to blame for your pedal feel.

Isnt the regular e30's clutch m/c like 20mm? Swap to that, it'll get softer.

I have e30 m3 brakes so the master cylinder should be correct for that setup

[matt]

There are two different master cylinders... one for brakes, one for clutch.

Your brake master cylinder has nothing to do with how your clutch feels. Your clutch master cylinder has everything to do with it.

You need a lesson in how your clutch works, sounds like.... your brake booster doesn't have anything to do with it either.

[Jason89i]

Hi dave -

i have had the e36m3 and e36 slave. i believe the e36m3 slave is a lot "softer" and has a larger bore diameter. i currently have it in my s52m3. i did notice (with the other white car) that one vendor sent me a standard e36 slave (in lieu of the e36m3 one i ordered) and it did feel a bit stiffer. you drove it, not sure if you noticed it was a bit stiffer than my current car.

cheers, jason

[erik325i]

The size of the master cylinder is 100% to blame for your pedal feel.

Isnt the regular e30's clutch m/c like 20mm? Swap to that, it'll get softer.

I know people swap out the brake master cylinders, but I didn't know you could swap out the clutch master cylinder for different sizes. Maybe I can get a larger master for my clutch because my clutch pedal is too soft...


-Erik

[1990m3]

There are two different master cylinders... one for brakes, one for clutch.

Your brake master cylinder has nothing to do with how your clutch feels. Your clutch master cylinder has everything to do with it.

You need a lesson in how your clutch works, sounds like.... your brake booster doesn't have anything to do with it either.

The clutch has a slave cylinder, not a master cylinder. I'm including the braking system in my parts list because the whole system is linked together. It uses the same hydraulic fluid as the brakes. You're right, I don't understand why my clutch pedal is stiff, but I do understand how the system works.

Jason - you drove my car...it still is significantly stiffer than your white or black car are. Not sure what the deal is. I'm going to take a look at the slave cylinder again and pull off the trans and make sure everything is lined up properly. Got any other ideas?

[matt]

The clutch has a slave cylinder, not a master cylinder.

OK, whatever you say.

[FredK]

Matt is right.

The only relation between the hydraulic systems is that the clutch and brake systems share a reservoir. That's it. The clutch pedal is connected to a
clutch master cylinder, which in turn actuates the slave cylinder.

21521156000 is the clutch master, 21521116300 is the clutch slave in a regular 325i.

That said, I've never heard of a E36 PP and JUST using the spring hub clutch disc from the M5, together with a stock thickness lightweight flywheel. Please correct me if I'm wrong! I just want to help you track down this problem and if it's a clutch disc / PP issue, it shouldn't be hard to address (well, except the dropping the trans part of it all!).

I believe the only flywheel made for the E34 M5 clutch is the UUC one. They have two lightweight flywheels, one for the stock E36 M3 clutch, and one made for the M5 clutch. Most E36 owners complain the pedal action is too light after switching to the E34 M5 setup and a UUC flywheel, not the other way around. I think there's something wonky with your setup.

[FredK]

I've attached a picture of the clutch system. You'll notice the lack of any brake boosters and brake MCs in the clutch hydraulic circuit.

[1990m3]

fair enough, my apologies. I didn't realize there was a master cylinder at the base of the pedal, I thought it was only visualizing the slave cylinder.

Which pressure plate do you suggest? Bimmerworld claims they have many clients using the m5 clutch disc with their LTW flywheel. My friend has the same setup as mine (s52 e30) and his pedal feels normal. Mine has no apparent friction point and is just generally stiff like a diesel big rig. Maybe there is something wonky with my setup. Right now my engine and trans are out of the car so it's easy for me to swap parts around.

[FredK]

Doesn't Bimmerworld suggest reversing the E34 M5 clutch disc for the install, or something strange like that?

Unfortunately I don't really have any experience with other clutch setups besides the stock E36 one.

[1990m3]

yes they do, and yes I did reverse the clutch. I have no ltw flywheel rattle as a result, none! I initially thought that was the problem and I was going to switch it back, but Bennetts22 on this board has done that also with no problems. I'll have to call him to see which pressure plate he used...

[Jason89i]

I have no ltw flywheel rattle as a result, none

im so jealous. mine rattles like a marble in a coffee can.
i would bet its the slave or pp (pressure plate). ive had pps go out on me before, they either go mush or get the big rig syndrome. ive also had certain vendors give me the e36 slave in lieu of the e36m3 one. they look the same, but the e36m3 one gives a SLIGHTLY softer pedal feel. check the part number on the pp to find out what it is. (i bet its the m5 one.) check for bent forks. cheers, jason