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Discussion Starter · #1 ·
Question for clutch experts re disc/plate/flywheel wear pattern

2001 M5, 27k miles.

The clutch has been feeling "soft" on 2-3 upshifts for some time now and getting "softer"...i.e. tiny bit of slip. Recently the 1-2 shift has been soft on a run up through the gears also. In addition, I tried a launch the other night and got slip trying to hook up which I've not had prior (launching ~ 1800-2000rpm then properly engaging clutch with throttle). Given these symptoms and the general weakness of the small clutch design, I made the decision to fix it before it got real bad plus with Oktoberfest HPDE and autocross right around the corner, I wasn't going to take the chance of missing out on fun at track.

I know the whole story behind the stock clutch versus UUC's large clutch versus their direct fit clutch, etc., but I'm planning on installing the stock items again anyway due to time constraints coupled with the issues UUC is trying to resolve with their direct fit clutch (which had been my plan).

Ok, enough background info.

Examining the pressure plate, disc and flywheel just now, there is a wear pattern whereby the outer 1/3 of each appears to be "worn more" than the remainder of the surface. For example, on the flywheel there are factory circumferential grooves on its surface which you can still plainly see and feel except on that outer 1/3 or so of the engagement area where it has a more polished look to it and is smooth. Similarly on the clutch disc you can see what appears to be more wear in that region. Same deal on the pressure plate.

Examination of the pressure plate shows nothing unusual about the SAC mechanism or the spring fingers. The plastic parts of the SAC are still intact and factory looking. There is no evidence of overheating anywhere.

I have decided to install a new flywheel along with the the disc/pp since I can't guarantee the flatness of the whole flywheel surface, and I don't want to take any chances. I have my opinion of this whole deal, but I would like anyone with a lot of past clutch experience to comment, if possible, on their take on the situation, especially from a BMW warranty perspective if possible.

Thanks,
Chuck
 

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Re: Question for clutch experts re disc/plate/flywheel wear pattern

CSBM5 said:
2001 M5, 27k miles.

The clutch has been feeling "soft" on 2-3 upshifts for some time now and getting "softer"...i.e. tiny bit of slip. Recently the 1-2 shift has been soft on a run up through the gears also. In addition, I tried a launch the other night and got slip trying to hook up which I've not had prior (launching ~ 1800-2000rpm then properly engaging clutch with throttle). Given these symptoms and the general weakness of the small clutch design, I made the decision to fix it before it got real bad plus with Oktoberfest HPDE and autocross right around the corner, I wasn't going to take the chance of missing out on fun at track.

I know the whole story behind the stock clutch versus UUC's large clutch versus their direct fit clutch, etc., but I'm planning on installing the stock items again anyway due to time constraints coupled with the issues UUC is trying to resolve with their direct fit clutch (which had been my plan).

Ok, enough background info.

Examining the pressure plate, disc and flywheel just now, there is a wear pattern whereby the outer 1/3 of each appears to be "worn more" than the remainder of the surface. For example, on the flywheel there are factory circumferential grooves on its surface which you can still plainly see and feel except on that outer 1/3 or so of the engagement area where it has a more polished look to it and is smooth. Similarly on the clutch disc you can see what appears to be more wear in that region. Same deal on the pressure plate.

Examination of the pressure plate shows nothing unusual about the SAC mechanism or the spring fingers. The plastic parts of the SAC are still intact and factory looking. There is no evidence of overheating anywhere.

I have decided to install a new flywheel along with the the disc/pp since I can't guarantee the flatness of the whole flywheel surface, and I don't want to take any chances. I have my opinion of this whole deal, but I would like anyone with a lot of past clutch experience to comment, if possible, on their take on the situation, especially from a BMW warranty perspective if possible.

Thanks,
Chuck
If you wish, you can guarantee (measure) how flat your flywheel is with a $5 metal straight edge ruler from Home Depot & a $5 feeler gauge set to measure ole' point or spark plug gap.

Your clutch organic surface wear pattern is 100% normal for the Luk OEM setup. Outer radius wears a lot more in most all cases & I think it has to do with uneven force that the marcel spring places on the disc surface. If you're still paranoid, a 9" straight edge will prove your low mile flywheel is flat & not worn in the shape of a dish (lol). I've seen it before....I bet the flywheel is flat. jusfugedabudit.........
 

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Re: Question for clutch experts re disc/plate/flywheel wear pattern

Thanks. I'll check it out with the straight edge -- good idea. It is so smooth and polished compared to the other 2/3's, its hard to imagine it being fully flat. After examining the stock pressure plate, I'm a bit sick with the thought of installing a new stock one, but time constraints force the deal at this point. If I could, I would at least get the non-SAC plate from UUC and use the stock disc at the moment.

That said, a board member has ~15k miles on a new stock setup and it has seen well over 2000 miles of track time running two drivers during each event (he in instructor group, his wife in A-group), and his clutch is fine. Hooks up hard, firm on all shifts, etc... If treated from day one with mechanical respect for the part and knowledge of its shortcomings, it obviously can last under some heavy use. You know the other part of this thought process is that with the 15% CCA discount, a stock clutch job at my dealer (parts and labor) is $890.80 -- not really that expensive imo. I know if I had to do a clutch on the V70R it would cost ~$1400 for example.
 

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Re: Question for clutch experts re disc/plate/flywheel wear pattern

CSBM5 said:
Thanks. I'll check it out with the straight edge -- good idea. It is so smooth and polished compared to the other 2/3's, its hard to imagine it being fully flat. After examining the stock pressure plate, I'm a bit sick with the thought of installing a new stock one, but time constraints force the deal at this point. If I could, I would at least get the non-SAC plate from UUC and use the stock disc at the moment.

That said, a board member has ~15k miles on a new stock setup and it has seen well over 2000 miles of track time running two drivers during each event (he in instructor group, his wife in A-group), and his clutch is fine. Hooks up hard, firm on all shifts, etc... If treated from day one with mechanical respect for the part and knowledge of its shortcomings, it obviously can last under some heavy use. You know the other part of this thought process is that with the 15% CCA discount, a stock clutch job at my dealer (parts and labor) is $890.80 -- not really that expensive imo. I know if I had to do a clutch on the V70R it would cost ~$1400 for example.
is the BMWCCA discount only on parts or does it apply to labor as well?
 

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Re: Question for clutch experts re disc/plate/flywheel wear pattern

At my dealership, they give at 15% discount on parts and labor. Most dealerships only have parts discounts in my experience.
 

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Re: Question for clutch experts re disc/plate/flywheel wear pattern

CSBM5 said:
Thanks. I'll check it out with the straight edge -- good idea. It is so smooth and polished compared to the other 2/3's, its hard to imagine it being fully flat.
Organic compound disc can slowly polish "tool marks" found on a flywheel, but it can not significantly wear it down...as measured in thousandths of an inch. You will discover that flywheels are refaced for three reasons and uneven surface wear is not one of them:

1) warpage from overheat (very rare, unless accompanied by massive cracks)
2) Gouging from rivet contact (refacing works well)
3) remove surface cracks from overheat (refacing does not work well, since cracks go deep...will reappear)

If we're talking about abrasive racing discs (largely non-organic), some wear can occur.
 
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