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Discussion Starter #1
Certainly the shortcomings of the stock clutch are well documented, as are many aftermarket alternatives. But I have not seen many discussions dedicated to replacing the clutch with stock parts. For someone who does not want to spend $3k on a replacement clutch and does not take their car to track days (I took the forum's advice and bought a dedicated track car instead of mod'ing the beast), what lower cost clutch options are there?
 
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b2g said:
Certainly the shortcomings of the stock clutch are well documented, as are many aftermarket alternatives. But I have not seen many discussions dedicated to replacing the clutch with stock parts. For someone who does not want to spend $3k on a replacement clutch and does not take their car to track days (I took the forum's advice and bought a dedicated track car instead of mod'ing the beast), what lower cost clutch options are there?
Here are some lower cost options: SPEC Clutch Kits.

Cheers, Daniel.
 

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b2g said:
Certainly the shortcomings of the stock clutch are well documented, as are many aftermarket alternatives. But I have not seen many discussions dedicated to replacing the clutch with stock parts. For someone who does not want to spend $3k on a replacement clutch and does not take their car to track days (I took the forum's advice and bought a dedicated track car instead of mod'ing the beast), what lower cost clutch options are there?
b2g,

Two disturbingly popular options seem to be: 1) replace the undersized clutch often or 2) trade-in. Many folks take a short-sighted approach that ignores recurring failures & labor fees. They simply don't want to fork out the necessary funds for the proper hardware upgrade to correct this factory flaw once and for all (tiny SAC mated to beast motor and girthy chassis).

Three OEM-size Spec clutches have reportedly been installed by members of this forum. One slipped after replacement and resulted in trade-in for an X5 SUV. The other problematic Spec clutch was replaced twice due to out-of-box defect and the second kit has apparently been working for a month or so. This 2 out of 3 failure rate may atypical, but I don't know. Time will tell.

Choosing a stronger clutch requires careful technical consideration. This is because methods used to increase torque capacity of an undersized clutch invariably decrease streetability. It's much like installing race brake pads with elevated temp range. The clutch will become more grabby and difficult to modulate.

USA domestic V8 cars with engines producing over 200 HP invariably come with clutches over 10" in diameter. This has been the rule for 30+ years. In fact, all domestic V8 cars built for the last 20 years with over 230 HP have clutches at least 10-1/2" in diameter. Note that these domestic car clutches are sized for street, not track. These substantial clutches last "long enough" on the street...not too long (lol). Under severe duty race conditions, OEM 11" clutches found in a Corvette or similar car are, in fact, inadequate. Folks with C4 and C5 Corvettes typically see 30K mile longevity, if they're regularly churning tires or launching hard with their 11" OEM setup.

Domestic sports cars and ponycars exhibit "decent" clutch lifecycles on the street. BMW V8 cars do NOT exhibit decent clutch lifecycles on the street. Hmmmm! Both designs use diaphram-type single organic disk setups with marcel for smooth engagement. Both have "high force" pressure plates. The question of "why the difference in lifespan" boils down points to swept area & diameter. SAC is not always at fault, but it surely does contribute to the problem.

Lower cost M5 clutch options are invariably 9-5/8" diameter. This is a problem, when we're talking about a 2 ton, 400 HP car with 10" wide tires and almost 52/48 weight distribution. These cars do not churn tires easily because they have substantial traction compared to a noseheavy ponycar. As such, the clutch tries to slip instead of the tires. Small clutches with a greatly elevated torque rating will not offer smooth streetable operation because they must resort to race materials and design. This involves harder, hi-temp disc materials that you don't even find in most exotic sports cars. These racey setups offer rough on-off engagement action. I'm not sure passenger whiplash or chattery action is desireable in a $75K 4dr to save a few bux.

I will also caution you that folks with 280HP 540i cars who drive aggressively on the street are having similar clutch longevity issues. It's tiny clutch is virtually the same as M5 (9-5/8").
 

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Discussion Starter #4
Lscman,

I have read your posts on clutches in the past and definitely agree that the 11" would be the way to go. I'm just not sure I want to shell out that kind of money. The M5 is BY FAR the best car I've ever owned. But, I'll be working out of the house beginning in March and unfortunately (or fortunately) I doubt I'll put enough miles on the car to require another clutch. So I'm wondering if I should go with a stock clutch or is there something else I should be looking at. I'd rather put the money toward a SSK or wider front wheels.

BTW, a friend of mine has a 540 and his clutch went out with 45k miles on the clock. So you're dead-on.
 

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Same here,

Stock clutch may the wrong way to go, and the 11" UUC setup just costs a lot of money. For me the return of the original flywheel is not an option (shipping would kill me).

We dont have any tracks over here, just the one 1/4 strip, and some auto-X meets.

So I am looking for a clutch that can take some punishment acceling hard from traffic lights and so on.

Stock Sachs = $300 (give or take)
SPEC stage 3-5 = 700 (give or take) + a flywheel $400
UUC stage 1-3 = $3.500 (give or take)

So Im thinkin, the UUC is by far the best setup, but how often would I submit my car to that kind of punishment. Im not much of a burnout fan, and I try rev-match and protect my clutch as much as I can. I just want a clutch that can handle some hard takeoff's and aggressive driving, but still isnt hard to use in normal driving.

For the difference in price of a UUC and a SPEC stage 5 + flywheel I could almost get a Tubi cat back exhaust.

I really need some good advise on this one. I know that this subject has been covered more often than you experts can take. Us (the normal M5 owner who does not know wery well what to buy) would love some kind of a comparison table and buying tips database.

Still, thanks guys for your current input.
 

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Fart said:
Same here,

Stock clutch may the wrong way to go, and the 11" UUC setup just costs a lot of money. For me the return of the original flywheel is not an option (shipping would kill me).

We dont have any tracks over here, just the one 1/4 strip, and some auto-X meets.

So I am looking for a clutch that can take some punishment acceling hard from traffic lights and so on.

Stock Sachs = $300 (give or take)
SPEC stage 3-5 = 700 (give or take) + a flywheel $400
UUC stage 1-3 = $3.500 (give or take)

So Im thinkin, the UUC is by far the best setup, but how often would I submit my car to that kind of punishment. Im not much of a burnout fan, and I try rev-match and protect my clutch as much as I can. I just want a clutch that can handle some hard takeoff's and aggressive driving, but still isnt hard to use in normal driving.

For the difference in price of a UUC and a SPEC stage 5 + flywheel I could almost get a Tubi cat back exhaust.

I really need some good advise on this one. I know that this subject has been covered more often than you experts can take. Us (the normal M5 owner who does not know wery well what to buy) would love some kind of a comparison table and buying tips database.

Still, thanks guys for your current input.

Use caution with the stock Sachs option. After some investigation, I am concerned that Sachs is bundling "superceded" Luk pressure plates with their own disk and throwout bearings. Luk pulled a trainload of early vintage SAC clutches out of inventory and may have recycled them thru non-BMW sales channels. A Sachs Techie almost admitted this to me. FYI, Sachs pressure plate IS Luk-built. This means you may be getting an old, troublesome Luk SAC pressure plate design. If you're going to choose and OEM-ish kit, the best bet is probably sourcing from BMW to get the latest iteration of the Luk package. Their stock turnover is "brisk" for M5 clutch kits (lol), so there's no old stuff around.
 

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Also be advised that clutches that have seen significant slippage WILL need a fresh flywheel. This is a costly, complex repair job.

The best price for OEM BMW or Sachs factory-quality parts is closer to $1250, if you include a fresh dual mass flywheel.

I would not reuse an overheated dual mass. If a clutch job is done properly, a flywheel that has seen significant slip is generally replaced. The flywheel surface will become heat-checked and the dual mass system is very heat-sensitive. A cooked dual mass can result in malfunction or chatter with a fresh clutch.
 

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Fart said:
My clutch is not slipping, except if I shift hard from 2. to 3rd. and 3rd to 4th.

But it does rearly happen.

I still want to change the clutch before the flywheel starts to cook.
Hey, maybe flywheels don't overheat in Iceland?!. All kidding aside.....sounds like a good plan to change before slip becomes pronounced. This may allow you to install a clutch kit without a fresh flywheel. This recipe works, so long as you're satisfied with your OEM-ish failure rate, limited torque capacity, limited severe-duty performance envelope & recurring labor fees. If you keep the car for a long time, it may not be the cheaper option.
 

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I'm having this exact debate with myself. I just can't afford the UUC option, as much as I would like it. Add another $700 for installation. Ughhh.
The SPEC kits are having issues. So the stock option is making sense. I've got 45K miles on the clock. If a replacement stock clutch and flywheel lasts the same, that's not too bad. But then I think I'm going to get a chip one day, maybe an intake. Now the UUC clutch makes more sense. Damned, right back to where I started. All the things I want such as a chip, UUC short shifter with dssr, home made intake can all be had for the price differential between the stock setup and the UUC opton. That's tough to swallow. But if you can't get the power to the ground....I just don't know.

B2G...sounds to me like the stock setup will do you just fine.

LSCMan....interesting about the old kits. I've seen stock M5 clutches on eBay for under $400. Wonder if they are out of date??
 

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This recipe works, so long as you're satisfied with your OEM-ish failure rate, limited torque capacity, limited severe-duty performance envelope & recurring labor fees. If you keep the car for a long time, it may not be the cheaper option.
I am not satisfied with the OEM setup, thats why Im seeking advice. Its a question of the most bang for the bucks without having the car at the dealer every for a clutch replacement.

Does anyone have the torque specs for the SPEC stage 1-5?<!-- / message -->
 
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There are a few more clutch/flywheel options to consider. These are available from BeastPower:

- G-POWER clutch set GP R - E39 M5 5,0l amplified.
- Rogue Engineering Lightweight Flywheel for M5 (e39).

Cheers, Daniel.
 

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boostmiser said:
I'm having this exact debate with myself. ...........LSCMan....interesting about the old kits. I've seen stock M5 clutches on eBay for under $400. Wonder if they are out of date??
Safe bet. BMW & LUK have rolled out several running changes in the OEM pressure plate sine 1999. The latest rev was released less than a year ago. There is no known way to determine vintage.

You couldn't "give me" an out-of-date OEM-based kit. Ebay is not a good source for this reason, as you'll likely be getting NOS (new old stock). It's been rumored that Luk has been tweaking the kit (with limited success). It seems a serious SAC failure problem was addressed a couple years ago, followed by one or more spring & mechanism tweaks. Anyway, the substantial labor involved & countless rev's makes it unwise to choose kits of unknown vintage from unknown sources.

A full OEM kit job with labor and flywheel is around $2K.

A full UUC kit job with labor and flywheel is around $4K.

These "loaded" cost numbers are the one's I use to compare. Assuming a used dual mass flywheel to be "good" for another full service cycle in this over-dutied application is awfully optimistic, IMO. They are sensitive to age & heat (failure-prone) & simply do not last.

IMO, the 11" UUC solution is "more than twice as good" compared to OEM and it'll likely last "over twice as long". Folks intending to keep their car for a long time should consider recurring labor charges & long-term performance and durability ramifications. As such, it may cost less in the long run to run the optimal setup. This is especially true for folks failing clutches every 50K or less.

There is a substantial group of folks out there who customarily trade-in every 3-5 years and already have their eye on a new M5 or equivalent beast. To be clear, I am not speaking to this group. My commuter car is 17 years old & has 280K mi. :cheers:
 

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Comparing a 9-5/8" race-material clutch to BMW's 11" 8-series street-organic clutch is interesting.

This is like comparing an M5 with factory brake system and race pads to an M5 with a StopTech brake kit and premium performance dual-duty pads. Both systems seem to hold up & stop hard under race duty, but the hotter factory rotors fail much sooner. They take a terrible beating from aggressive race pads combined with lesser brake hardware. Alternatively, the oversize StopTech system has the ability to absorb more heat while keeping rotor surface temps within the operating range of the perf street pads. Take these 2 setups on the street and the StopTech setup with lower temp street pads behaves excellent, just like stock. The race pads and OEM rotors will chatter & squeak and cold panic stop performance will be poor. Modulation with race-compound materials will be poor at typical street temps.

WRT clutches...the high temp, hard compound disks with no marcel will, in fact, allow a 9-5/8" clutch to grip quick under severe duty. This is because the friction coefficient of the race material is impressive under extreme heat. The problem with this setup is it gives everybody whiplash and subjects the flywheel to race-level surface temps. This is not good because: 1) dual mass is not designed for this & 2) racers check and change their abused single mass flywheels on an aggressive service interval. This plan where the flywheel sees race-level temps & service requriements is counterproductive from a cost standpoint. Race clutch NVH issues mean your tasteful 4dr saloon will likely exhibit unnecessary driveability & harshness issues.

OEM rotors that have been destroyed by race pad temps can be changed in 1/2 hour. The same can not be said for a heat-checked or damaged flywheel. This is the fundamental problem with running a small race clutch. To me, accelerated brake service intervals are a "manageable annoyance" (acceptable)....while recurring clutch repairs are not.
 
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