On the B8 (and B6/B7) the clutch fluid is shared with the brake fluid, via a slave cylinder. My ridiculously over specified Brembo brakes can handle the heat just fine. My clutch system cannot and if I’m too busy with the gears at the track, I get bad clutch slipping.
What happens is about 10 minutes into a session, the clutch pedal doesn’t come all of the way back up on every shift. It will sort of stick half way down. To avoid it, I’m shifting less. I’m making sure I slightly over-rev (instead of under-rev) the downshifts. I let the clutch out more slowly and deliberately, also known as grannie shifting.
What are my options for fixing this? Can I have two master cylinders and separate the systems? Should I go back to JHM and switch from the stage 3 organic/metal hybrid disc to the stage 4 kevlar/kelvar disc?
The sticky clutch pedal is a common problem with the B7 RS4s. It has to do with the self-adjusting clutch mechanism of the pressure plate. The RS4 guys have been switching to the JHM R-series pressure plates and clutch discs. The stage 3 and 4 JHM clutch kits for the B8 S4s use a upgraded Luk pressure plate that has a self-adjusting clutch mechanism. I would replace the clutch and pressure plate with the 1R or 3R clutch kit along with the flywheel liner, throw-out bearing, and hardware. You probably have to call JHM for the R-series clutch kit because I don’t think that it is on the website yet.
By the way, here is a link to a post in my Jimmy’s Garage thread that talks about installing a 5R clutch kit.
The heat issue is with the clutch not the fluid. The fluid feed to clutch master comes from the brake res. the coolest area of brake fluid during a session
I am aware that West has a B8 S4. He is likely slipping the clutch a lot while on the track and by this point he probably needs a new clutch anyways. How many track days do you think that West has on the stage 3 clutch kit? Probably at least 30, maybe 40. Sadly it is a consumable part just like tires and brakes.
It really only sticks after turns in which there is extreme braking. With my vBox data, I can see I do 123 MPH in section 1 of Laguna (downhill), which immediately connects to a 38 MPH minimum speed in section 2. The car can do a 4-3 shift, but if I do a 4-2 shift then the 2-3 sticks.
This is just something I’ll have to live with until I start tracking a car with a proper PDK.
Do you use a lot of motor breaking during that time. I would guess not right. That would slow the car down. I see your point on the heat and the direct relationship with the PP not responding. After the sticking 2-3 shift will it come back to life again and work normal. Or is it like that for the rest of the lap
Saki, I am pretty sure that JHM have the 1R and 3R for the B8s. Dru was recommending the 3R for the B8 S4 that I put the 5R in. To be honest it would have been better to go with the 3R because the 5R is pretty aggressive but live and learn. None of the R-series clutch kits are on the website though. If they only have the 5R then that is news to me.
wonder if they have them yet, they tried to put one in my car as a test and it didn’t engage right since it was for a different platform than the b8 at the time.
Im really wondering if this really is a problem with the clutch hydrolics heating up.
If it is I would attempt to change out your slave cylinder for a new one and maybe even the master.
Are you running a stainless steel clutch line? The OEM line runs right by the exhaust manifold which transfer a lot of heat to the clutch fluid. When I installed my USP clutch line I was able to run the entire line behind the heat shielding! This helped with my clutch problems. I was getting the squeaky/grainy clutch feel when the car heated up. Now I’m encountering the problem far less and it’s reduced in severity.
Unfortunately I really feel that your problem is occurring because the pressure plate is heating up. In that case I really think you need a new pressure plate and clutch while you’re at it. I’m really loving my JHM stage 4
yes the sticky clutch issue that so many RS4 owners complain about comes on 2 ways
revving the car while parked with teh clutch down. Let go of the clutch pedal after the revs are done and the clutch will stick to the floor or half way. Or, if you’re near the top of the RPMs while driving, and you push the clutch pedal to the floor (say to coast in neutral and leave it down) it will stick after that. This happens when logging for example when you hit redline and push the clutch pedal in…or happens at the dragstrip when you’re deep into 4th gear and after you cross the line if you push the clutch in to chill out. Stickysauce. I always just let it rev down in those situations
slip the clutch typical of poor driving/poor engagement. This is likely what west is doing, since we know he’s not that great at changing gears briskly or accurately (see his quartermile vid…he takes a month between gears and slips engagement each time)
Having put 90,000 kms on my stock RS4 clutch (along with teh 45,000 the previous owner put on) it is still perfect, holds hard, rips hard, but if I fuck up a gear shift and get it wrong, or don’t rev match properly, or mess up engagement, sure enough it will stick. Happens about once every 2 months, generally when I’m gearing down and revmatching a downshift for aural inspiration. Normal hard driving, no problem.
So Jimmy I bet you’re bang on with your assessment. Problem is if you’re a bad driver and slip the R series clutches, you’ll fuse them. Best thing for west to do is buy a B8 S4 with DSG. Or another bitchster.
I mean, am I shifting slow because the clutch is sensitive? Or because my neurons fire slowly and I lack coordination, depsite my amazing footwork with the accelerator and brake, and an accurate hand on the wheel that can hang 4" of tire in the dirt at an apex five times in a row?
Clearly my next car will be another PDK. Why would I want to deal with this crap again when Porsche has solved it for every level of track car? Now that they are in the turbo game across the whole linup, we will see how good the PDK is on reliability.
West did you every hit JHM up about this. They are usually very good with customer service. I would e mail them and see what they say.
I know for the higher hp cars they have some of the R line solutions and for the kind of racing your doing and the abuse the clutch takes in some sections of the track they might have some more input.
Yeah I got in touch with JHM and they said they can do a 5R. I will investigate the stainless steel clutch line relocation and see if they provides any relief. It’s not critical because it has a workaround, it’s just something I need to address eventually.
