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Discussion Starter #1 (Edited)
www.speclutches.com


i purchased a stage 3 with lightweight option and flywheel. it has been in my M5 for 3 days, and WOW what a difference! a friend that races mustangs told me about spec... he says he'd be very suprised if i could tear up this clutch with a 400hp car. so if anyone wants an upgraded clutch and doesn't want to spend UUC $ this might be for you(i paid $1500.00 for everything listed).

i'll keep everyone posted as i rack up the miles :wroom: . i finally feel i have a 400hp car ;)

the dealer (yes, BMW) was so pleased with how my car turned out, they are now a SPEC vendor.
 

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that product looks very promising. Nice website, and good list of different style clutches. Good luck, and let us know how it works......i'll most likely use them as my next clutch, whenever that will be.

-Jonathan
 

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Wanna hear something even better...

SPEC Is the maker of the Flywheels and clutches for UUC...but they take the 850 csi size clutch and mate it to a new flywheel for UUC...not a standard size M5 disk.

The spec stg 4 is equiv of the UUC stg 3....
 

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The best combo for street M5 is an organic disk combined with a big clutch.

1) aluminum flyheels are not for street use. A street car needs stored kinetic flywheel energy to launch smoothly and effortlessly at light throttle. A heavy street car with a light flywheel is the worst combo. An aluminum flywheel in an M5 will exhibit excessive rollover noise.

2) clutch diameter/swept area needs to be large for street use.
A small clutch may, in fact, hold up well in a race-only track car if a super high temp, grabby, whiplash-inducing ON-OFF clutch material is employed. The problem is...the resulting clutch behavior is not suitable for a tasteful 4dr street car. Street cars need a clutch that can be smoothly engaged while providing a couple seconds of low-throttle slip under certain parking/maneuvering conditions.
 

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dbox said:
www.speclutches.com..i purchased a stage 3 with lightweight option and flywheel...
Very nice :cool: Did you get the aluminum flywheel? Is it the stock diameter? How's the rollover noise? Is it "grabby" at all?
 

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Good post, I will definately keep this option in mind when my clutch finally goes (crossing my fingers right now, 40k and counting).
 

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We've been using SPEC as the manufacturer of our exotic-material clutch offerings for about two years now. In fact, we're a SPEC distributor and offer all fitments at a significant discount from SPEC's online price. It's no secret... our website and online order forms say "SPEC Stage (X)" in the options list.

While the SPEC Stage3/4 material may have greater capabilities than the same-size organic disc, the same abuse from an inadequate size still affects the longevity... and the smaller size is definitely more "grabby" than the larger size we use in the UUC V12 clutch conversion simply due to a smaller area of material being responsible for the complete engagement.

But in all reality, that's only half the story with the E39 M5 clutch problem... the other part of the equation is the problems with the pressure plate.

SPEC's OE-fitment clutches use "enhanced" pressure plates for more clamping force, the same OE plate you get in a new BMW clutch. What this means for M5 owners is that the SPEC E39 M5 pressure plate retains the Self Adjusting Clutch (SAC) mechanism. To quote from the explanation on our website:

Many E46 3-series and E39 5-series owners have experienced mushy clutch feel, inconsistent engagement, and premature wear of the clutch in their manual-transmission cars.* The reason is quite simple - the original BMW (LUK-manufactured) clutch in the E46 and E39 has a new "SAC" (Self Adjusting Clutch) design.* This new mechanism built into the clutch pressure plate is supposed to keep the clutch pedal engagement point the same as the clutch wears... but in all reality, it's a case of* "an answer to a question that nobody was asking." They have added a layer of complexity and feedback isolation, filling a need that didn't need filling - it is not too often that anybody notices that their clutch engagement point as moved 1/2" over 50K miles.

The SAC mechanism itself causes problems; it over- or under-adjusts the pressure plate and therefore causes the clutch to slip or burn out prematurely. They are also known to shift, causing the pressure plate release fingers to slip off the plate, keeping 1/3 of the pressure plate engaged at all times. Bottom line is that the only fix is a complete clutch job, and your dealer is likely to claim "driver abuse". We have seen it happen too many times.

The SAC mechanism may not give a clean release like a standard clutch. Instead of just two sets of springs, there is an adjuster mechanism that makes engagement feel mushy or slow.

The UUC M5/V12 clutch conversion eliminates the SAC mechanism and restores traditional clutch feel with predictable and crisp engagement.


It's no fault of SPEC that LUK designed this sort of mechanism... but it does mean that the SPEC product equipped with SAC still has the same flaws. All the same SAC-related problems that afflict your original E39 clutch afflict the SPEC clutch in the same fitment.

We've had limited luck with "locking" the SAC mechanism to disable it... but truth be told, that had only limited success. A hard shift, or a hard driveline lash shockload force, would still cause an "adjustment" - more accurately a "misadjustment" - and problems would arise. And no matter what is done to modify the SAC, the clutch feel is still that same disconnected, mushy feel.

An analogy to a different activity hampered by equipment is appropriate here, one could say driving a SAC-equipped clutch is like "taking a shower in a raincoat."

At this point, UUC refuses to sell any brand clutch with a SAC mechanism, regardless if the part comes from BMW or SPEC. The reliability/durability is simply not up to our standards.

We gladly offer SPEC products in the non-SAC fitments (and we can even provide a SPEC Stage1 organic disc as an option) as we do for the M5 and all of our other flywheel fitments.
 

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dbox said:
i purchased a stage 3 with lightweight option and flywheel. it has been in my M5 for 3 days, and WOW what a difference!
QUOTE]

dbox,
Thank you, you have given us some hope and hope is a powerful antidote.:) . I have a few questions:- 1. In terms of feel what is the difference between the stock clutch and the stage 3 clutch you installed? 2. For the normal driver who does not do track or drag racing but just simply want to know that he as a good clutch that can support the 400 hp the M5 bring is the stage 3 the ideal clutch? 3. Is there any empirical data that shows that the stage 3 is a better clutch than the stock clutch? Thanks in advance for your thoughts.
 

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Lscman said:
The best combo for street M5 is an organic disk combined with a big clutch.

1) aluminum flyheels are not for street use. A street car needs stored kinetic flywheel energy to launch smoothly and effortlessly at light throttle. A heavy street car with a light flywheel is the worst combo. An aluminum flywheel in an M5 will exhibit excessive rollover noise.

2) clutch diameter/swept area needs to be large for street use.
A small clutch may, in fact, hold up well in a race-only track car if a super high temp, grabby, whiplash-inducing ON-OFF clutch material is employed. The problem is...the resulting clutch behavior is not suitable for a tasteful 4dr street car. Street cars need a clutch that can be smoothly engaged while providing a couple seconds of low-throttle slip under certain parking/maneuvering conditions.
Question for LSCMAN,
What are your thoughts on DINAN's lightened FlyWheel? Im more interested in your opinion on the Stage 1 Lightweight Flywheel (Dual-Mass) .
Thanks!
Robert :M5thumbs:
 

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Discussion Starter #10
ELEVENS said:
Very nice :cool: Did you get the aluminum flywheel? Is it the stock diameter? How's the rollover noise? Is it "grabby" at all?
very grabby, i did get the flywheel...as far as i know its stock diameter. is rollover noise gear lash? if so, i do have it but its worth it to me to have the car drive the way it does now.
 

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Discussion Starter #11
Sonic M5 said:
dbox said:
i purchased a stage 3 with lightweight option and flywheel. it has been in my M5 for 3 days, and WOW what a difference!
QUOTE]

dbox,
Thank you, you have given us some hope and hope is a powerful antidote.:) . I have a few questions:- 1. In terms of feel what is the difference between the stock clutch and the stage 3 clutch you installed? 2. For the normal driver who does not do track or drag racing but just simply want to know that he as a good clutch that can support the 400 hp the M5 bring is the stage 3 the ideal clutch? 3. Is there any empirical data that shows that the stage 3 is a better clutch than the stock clutch? Thanks in advance for your thoughts.
the pedal feel of the stock clutch was much harder than this one. the pedal is so soft it takes some getting used to. barely push it in and you're ready to go. i went with stage 3 because i didn't want to worry about anything. funny thing is the dealer actually paid for this clutch. i purchased the car with 29500 miles...clutch went out at 33000. the used car manager paid for it since it's a CPO car. i'm sure i would have been ok with a stage 3, i'm also sure i didn't need the flywheel. i just wanted to get everything, you know how that goes :blink:
 

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Discussion Starter #12
Rob Levinson said:
We've been using SPEC as the manufacturer of our exotic-material clutch offerings for about two years now. In fact, we're a SPEC distributor and offer all fitments at a significant discount from SPEC's online price. It's no secret... our website and online order forms say "SPEC Stage (X)" in the options list.

While the SPEC Stage3/4 material may have greater capabilities than the same-size organic disc, the same abuse from an inadequate size still affects the longevity... and the smaller size is definitely more "grabby" than the larger size we use in the UUC V12 clutch conversion simply due to a smaller area of material being responsible for the complete engagement.

But in all reality, that's only half the story with the E39 M5 clutch problem... the other part of the equation is the problems with the pressure plate.

SPEC's OE-fitment clutches use "enhanced" pressure plates for more clamping force, the same OE plate you get in a new BMW clutch. What this means for M5 owners is that the SPEC E39 M5 pressure plate retains the Self Adjusting Clutch (SAC) mechanism. To quote from the explanation on our website:

Many E46 3-series and E39 5-series owners have experienced mushy clutch feel, inconsistent engagement, and premature wear of the clutch in their manual-transmission cars.* The reason is quite simple - the original BMW (LUK-manufactured) clutch in the E46 and E39 has a new "SAC" (Self Adjusting Clutch) design.* This new mechanism built into the clutch pressure plate is supposed to keep the clutch pedal engagement point the same as the clutch wears... but in all reality, it's a case of* "an answer to a question that nobody was asking." They have added a layer of complexity and feedback isolation, filling a need that didn't need filling - it is not too often that anybody notices that their clutch engagement point as moved 1/2" over 50K miles.

The SAC mechanism itself causes problems; it over- or under-adjusts the pressure plate and therefore causes the clutch to slip or burn out prematurely. They are also known to shift, causing the pressure plate release fingers to slip off the plate, keeping 1/3 of the pressure plate engaged at all times. Bottom line is that the only fix is a complete clutch job, and your dealer is likely to claim "driver abuse". We have seen it happen too many times.

The SAC mechanism may not give a clean release like a standard clutch. Instead of just two sets of springs, there is an adjuster mechanism that makes engagement feel mushy or slow.

The UUC M5/V12 clutch conversion eliminates the SAC mechanism and restores traditional clutch feel with predictable and crisp engagement.


It's no fault of SPEC that LUK designed this sort of mechanism... but it does mean that the SPEC product equipped with SAC still has the same flaws. All the same SAC-related problems that afflict your original E39 clutch afflict the SPEC clutch in the same fitment.

We've had limited luck with "locking" the SAC mechanism to disable it... but truth be told, that had only limited success. A hard shift, or a hard driveline lash shockload force, would still cause an "adjustment" - more accurately a "misadjustment" - and problems would arise. And no matter what is done to modify the SAC, the clutch feel is still that same disconnected, mushy feel.

An analogy to a different activity hampered by equipment is appropriate here, one could say driving a SAC-equipped clutch is like "taking a shower in a raincoat."

At this point, UUC refuses to sell any brand clutch with a SAC mechanism, regardless if the part comes from BMW or SPEC. The reliability/durability is simply not up to our standards.

We gladly offer SPEC products in the non-SAC fitments (and we can even provide a SPEC Stage1 organic disc as an option) as we do for the M5 and all of our other flywheel fitments.
so i am still screwed?
 

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dbox said:
so i am still screwed?
Clutch-wise, yes. The shockload forces on the pressure plate I referred to before are even more abrupt with the more aggressive material.

By the way, you already have experience with SAC failure. Your comments about the difference in pedal effort between the original bad clutch and your new clutch are specifically one of the symptoms of a SAC problem.

I suspect that if you keep that car, we'll be talking about your alternate options within a year.

- Rob
 

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The stock dual-mass flywheel is required for a complete absence of idle rattle. It can either be full-weight (assembly with clutch is 52 lbs.), or cut-down to 11.0 inch diameter to take off 7-8 lbs. (8 lbs. by my measure). This machining can either be farmed out individually to a competent machine shop (rebalancing required), or you can purchase a Dinan Stage 1 flywheel (modifications already completed).

However, with this approach you will be limited to a 240 mm (9.6 inch) diameter clutch. The two clutch upgrades that have been tried by Board members are: (1) to have a beefed-up pressure plate made by a specialty clutch shop, likely using the stock disc; and (2) use the pressure plate and clutch disc offered by Sachs Race Engineering (p/ns 748/978). This latter is a quite stiff pressure plate and a much higher quality bonded disc, and is not inexpensive. The downside of the Sachs clutch is that a raised area near the flywheel-to-crankshaft bolt circle needs to be machined down to clear the Sachs disc (the Dinan Stage 1 flywheel has this machining already done). You cannot use the stock disc with the Sachs pressure plate, as there is not enough pedal travel to obtain full release.

Pedal effort will be quite stiff with the Sachs race unit, but this can be brought down to an acceptable level (still stiffer than stock) by substituting the 26.99 mm. diameter slave cylinder. This combination is quite driveable on the street, is QUIET with the factory-recommended trans. lube, and does not even think about slipping behind my S2.

To give Lscman his due, things would be even better with a larger diameter clutch. However it is not practical to machine the stock flywheel to accept a larger clutch; one must use a single-mass flywheel such as the product offered by Rob Levinson or the custom steel flywheel made by Mark (MIB) and deal with the turnover noise.

Regards, Dick Roberts
 

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Michaelc said:
Rob,

My apologies if you have been asked this question before (perhaps many times!) but is there no option available for the E39 M5 of a standard sized but uprated clutch i.e. one that does not require a new flywheel?
The fundamental problem with the shortened lifespan of the M5 clutch is specifically tied to the basic clutch characteristics, thes two critical factors being 1) size, and 2) clutch/SAC design.

Size is size. You can't put a bigger clutch disc within the same pressure plate, and you cannot attach a larger pressure plate to the OE flywheel. Even with uprated material, the size is a factor because of too-small maximum clamping force of the pressure plate - the grabbiest material in the world is of little use if the pressure plate cannot adequately hold it between the high-torque motor and the high-mass chassis.

Clutch/SAC design is what I discussed previously. The only "conventional" direct-fit replacement is the Sachs Racing clutch that is designed for use on M3 racecars. It's still not a great solution because you have to modify your original flywheel, machine off an inner lip. With all the labor charges, plus the risk of getting shavings in the dual-mass mechanism, plus the fact that the dual-mass flywheels themselves are only rated for 3 clutch cycles (and usually die during the second or third anyway), that option loses it's attraction. So besides the modification difficulty, short flywheel lifespan, costs of modification labor and the almost $1K racing clutch, you even have one other issue - greatly increased pedal effort.


Failing that, are there flywheels available that do not cause the horrid chatter at idle?
Strictly looking at chatter (gear rattle - read more by clicking here) as an issue, any solid disk/solid hub clutch will be pretty noisy. Distinctions between brands are insignificant, the condition of the particular car's transmission is more of a factor.

But discarding all of those basic setups, there are only two options that do anything to significantly address the gear rattle.

One is the recent Dinan flywheel that is a modified/lightened BMW dual-mass unit. That retains the mechanism which cushings the power-pulse variations that cause the noise. It works well, but still uses the small OE clutch and retains all of the problems. Additionally, as the dual mass mechanism has a finite life, it is not rated for more than three clutch replacement cycles and will be discarded as part of normal maintenance procedure.

The other option is the sprung-hub clutch disk that UUC uses in the V12 clutch conversion, a design that has the torsional damper built into the clutch instead of the flywheel. This is the basic design of the large V12 clutch has the sprung-hub center as standard... the V12 850 CSi (same weight, power, and same-family gearbox as the M5) used a solid flywheel and this clutch. While there still may be a small amount of residual rattle, it will be dramatically less than a standard lightweight flywheel setup installed in the same car. The upside to this design is that the flywheel itself is a lifetime part, no mechanism to break (surface may need replacing about every 6 clutch replacements, but that's a $100 part). With every clutch replacement, the torsional damper mechanism is refreshed as it is built into the clutch.

- Rob
 

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Rob,

Is the mass moment of inertia of the UUC flywheel/clutch similar to the stock setup (i.e. do you know the radius of gyration and mass of each combination)? I know the UUC flywheel/clutch may be lighter than stock, but it does have a bigger diameter, so I'm hoping its moment of inertia is similar.

I would prefer not to lose the current level of stored energy of the stock setup as I find it just about perfect for launching the car hard and everyday driving.

Thanks,
Chuck
 

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For me the dual mass unit is a NECESSITY. I want no noise at all. The other necessity is for a stock mass flywheel. I am trying to operate within those parameters. Again, I have not seen any lightened-flywheel M5 turn really strong 1/4-mile times and absolutely did NOT like the feel of Dinan's lightened flywheel when driving on the street in an couple of S2s.

I am looking for options with those restrictions.
My options seem to be as follows:

- The SACHs unit with high effort pedal and possible slave cylinder mod

- Some combination of the SPEC products with organic disk

- A custom job by UUC, if possible
 

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CSBM5 said:
Rob,

Is the mass moment of inertia of the UUC flywheel/clutch similar to the stock setup (i.e. do you know the radius of gyration and mass of each combination)? I know the UUC flywheel/clutch may be lighter than stock, but it does have a bigger diameter, so I'm hoping its moment of inertia is similar.

I would prefer not to lose the current level of stored energy of the stock setup as I find it just about perfect for launching the car hard and everyday driving.

Thanks,
Chuck
I have a friend who also looks at the message boards once jokingly ask me, "Do you put up the website for your own amusement? I'm not sure anybody reads it..." :)

We strive to have every little detail of technical information anyone could possibly want just short of CAD files. The MOI data and calculations you seek are all right here:

http://www.uucmotorwerks.com/flywheel/m5_flywheel.pdf

Please let me know if you need additional info.

- Rob
 
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