Clutch Slipping on stock A91 MT...

[UYCR]

Hydro bearing failed on mine and it’s internal which is a ***** to fix when it fails.

the pedal does feel nice though

I saw your post about it. Are they going to be sending you a replacement? With how few are running it and how little it has been in the market as an option for us I would have expected them to react with some sort of urgency.

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[AJRMKV]

I saw your post about it. Are they going to be sending you a replacement? With how few are running it and how little it has been in the market as an option for us I would have expected them to react with some sort of urgency.

replacement arrives tomorrow, then we’ll open up the trans and find out exactly how this happened

 

[SupraCess]

This happened to me before with my boosted 86 right before track day. Smh!

 

[AJRMKV]

This happened to me before with my boosted 86 right before track day. Smh!

Failed slave cylinder/hydraulic release bearing that leaked fluid?

 

[BananaBoi]

I've made a full post about my experience here for those who care to read.

https://www.supramkv.com/threads/clutch-slipping-issues-and-warranty-denial.22940/

 

[Crool88]

I installed one of these today and it's a night and day difference, particularly on heel-toe downshifts where you have to be quick with the clutch to catch the engine revs at the right spot. Before I felt like I had forgotten how to heel-toe. Now it's very natural.

I think someone somewhere said this would be a five minute job.... yeah no. Not unless you have like two helpers and you've done it zillion times. ?

My notes on the install:

• Both bolts are a little tricky to get to and mine had a bit of blue loctite on them from the factory. Universal joints or wobble/swivel sockets help.
• A video I watched said to pull out the tip of the new slave before installing - don't do this. It just makes installation more difficult. It's "locked" in the closed position and there's a spring that pushes it out to full extension, but as soon as you put pressure to it, it's going to pop out on it's own. It's also just going to put more air in the system that you'll have to then bleed out.
• It took quite a lot of bleeding to get all of the air out. Be careful about that because you'll think (especially if not using a power bleeder) that you've got it bled, but you'd be wrong. I probably flushed the equivalent of four BMW bottles of brake fluid through it before I was really confident that I had gotten it all. I didn't have four bottles, but I was using a clean drain bottle so I put the fluid I drained out back in the power bleeder. (Definitely DON'T do this normally, but this car was built a few months ago and has under 1000 miles on it, all of the fluid I bled looked exactly like the new BMW fluid and I used a clean container to drain into. Just buy way more brake fluid than you think you'll need, the BMW spec stuff is cheap.)
• Now that I think about it, you might avoid some unnecessary bleeding if you have your new slave ready and disconnect the line from the old one and immediately plug it into the new slave. If you remove the bottom bolt on the slave first, the bracket holding the line comes with it and you'll be able to let it dangle out of the way while you work on the top bolt, which is easier to get to with the line out of the way. Otherwise, gravity drains a lot of fluid out of the line and the master.
• I used a Motive Power Bleeder, part number 0109. 15 psi as recommended worked just fine for this.I bought mine from Summit a long time ago, but you can get it from FCP Euro at the same time as the slave here: https://www.fcpeuro.com/products/european-power-bleeder-black-label-motive-products-mot0109 Note that there's some assembly required with these and you'll want some teflon tape handy to seal the threads on the connectors.
• If you use a power bleeder, you'll overfill your fluid reservoir. Have a syringe handy to suck brake fluid out of the reservoir until it's down to the "Max" level. I used one I had lying around that the vet gave me for shooting antibiotics down my cat's throat. ? Looks like this and works great: https://www.amazon.com/dp/B07P25XH8Z/
• I also used a Longacre brake fluid bleed bottle, part 52-45202. This thing has a magnet on it (which saves you time futzing around with zip ties or baling wire) and I hung it from the angled surface where the firewall is transitioning into the floorboard. Worked great in that position. https://www.summitracing.com/parts/LNG-45202
• I used BMW low viscosity DOT4, part number 81220142156. I assume the low viscosity helps in the winter with clutch feel/speed. Again, buy like four bottles just in case, particularly if you don't expect to be able to reuse your flushed fluid like I did. From FCP Euro: https://www.fcpeuro.com/products/bmw-brake-fluid-81220142156
• I bought my clutch slave from FCP Euro as well: https://www.fcpeuro.com/products/bmw-clutch-slave-cylinder-21526785964

Thank you for the details! Do you need any parts other than the new slave cylinder? I see someone mentioned a z-shaped piece of metal tubing. Is that required? If yes, do you any info on it?

 

[Spart]

Thank you for the details! Do you need any parts other than the new slave cylinder? I see someone mentioned a z-shaped piece of metal tubing. Is that required? If yes, do you any info on it?

I am not sure what that would mean but yes, I only needed the slave cylinder and fluid.

 

[kingdooksdb]

So I am experiencing the same issue with my twin disc… from first to second WOT it just doesn’t grab…. I have to trial and error because at first I thought it was my clutch and now I’m thinking it’s operator error… it’s quite possibly I’m not depressing the clutch fully while timing my stick shift it ‘whines’ briefly in the pedal before it grabs. I need to practice more and see if maybe I’m just an idiot and bad at shifting

 

[Spart]

So I am experiencing the same issue with my twin disc… from first to second WOT it just doesn’t grab…. I have to trial and error because at first I thought it was my clutch and now I’m thinking it’s operator error… it’s quite possibly I’m not depressing the clutch fully while timing my stick shift it ‘whines’ briefly in the pedal before it grabs. I need to practice more and see if maybe I’m just an idiot and bad at shifting

Forgive me if you've already mentioned it, I searched this thread for your name and didn't see you state anything about it: have you deleted your CDV yet? It's certainly not helping if you still have it.

 

[kingdooksdb]

Forgive me if you've already mentioned it, I searched this thread for your name and didn't see you state anything about it: have you deleted your CDV yet? It's certainly not helping if you still have it.

CDV was deleted upon installation of the current clutch which was done this week

 

[tharris4995]

CDV was deleted upon installation of the current clutch which was done this week

I have a dual disk clutch and I’ve found that if you drag it it hates you, if you just drop the clutch full out it loves you.
It wants to go.

 

[kingdooksdb]

I have a dual disk clutch and I’ve found that if you drag it it hates you, if you just drop the clutch full out it loves you.
It wants to go.

I appreciate your response I gotta chill a bit though I only put 50 miles on it before I opened it up and I don’t know how risky that is with the break in process. I really don’t wanna stress about it but here we are lmao

Edit: anyone with experience, is it the “end of the world” if I opened her up a bunch of times before a full break in? If I’m being fair I hit her from a dig I’d say once but I did test WOT from 1st to 2nd about 6 or 7 times to try and recreate the slipping symptom to which only one time I managed to. Most of the time my gear shifting even while WOT is conservative in the sense that I’m not flat foot shifting. My concern is hurting this brand new expensive clutch and having to spend money AGAIN because I’m an idiot

 

[tharris4995]

I appreciate your response I gotta chill a bit though I only put 50 miles on it before I opened it up and I don’t know how risky that is with the break in process. I really don’t wanna stress about it but here we are lmao

Edit: anyone with experience, is it the “end of the world” if I opened her up a bunch of times before a full break in? If I’m being fair I hit her from a dig I’d say once but I did test WOT from 1st to 2nd about 6 or 7 times to try and recreate the slipping symptom to which only one time I managed to. Most of the time my gear shifting even while WOT is conservative in the sense that I’m not flat foot shifting. My concern is hurting this brand new expensive clutch and having to spend money AGAIN because I’m an idiot

My mechanic (who is very well known in my area) advised me to break it in at low rpm’s. His suggestion was to not go over 3k rpm’s for the break in process.

 

[tharris4995]

I appreciate your response I gotta chill a bit though I only put 50 miles on it before I opened it up and I don’t know how risky that is with the break in process. I really don’t wanna stress about it but here we are lmao

Edit: anyone with experience, is it the “end of the world” if I opened her up a bunch of times before a full break in? If I’m being fair I hit her from a dig I’d say once but I did test WOT from 1st to 2nd about 6 or 7 times to try and recreate the slipping symptom to which only one time I managed to. Most of the time my gear shifting even while WOT is conservative in the sense that I’m not flat foot shifting. My concern is hurting this brand new expensive clutch and having to spend money AGAIN because I’m an idiot

I don’t think it would damage the clutch beyond repair, those dual disk clutches are designed to be abused.

just out of curiosity, does your clutch pilot bearing make a lot of noise at idle in neutral?

 

[kingdooksdb]

I don’t think it would damage the clutch beyond repair, those dual disk clutches are designed to be abused.

just out of curiosity, does your clutch pilot bearing make a lot of noise at idle in neutral?

Makes no noise it’s actually really quiet.

edit: I have a bad feeling it’s a faulty synchro ring. I’ve experienced this symptom with my original clutch and if after upgrading said clutch the issue persists it’s either driver error which is possible, or something transmission related which tbh might make me cry

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