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Discussion Starter #1
Hey guys looking for some guidance once more,

had the uuc stage III clutch and flywheel installed. a couple of question for anyone that may have this set up or someone that just might know about it.

1. will the chatter dissipate after the break in period? (very loud right now)

2. from a dead stop the car shakes a bit as the clutch is engaging in first (almost the same kind of vibration you get from a vibrating drive shaft) but stop right away and doesn't happen in any other gear. Thoughts?

These two issues aside, the clutch feel great. A signficantly lighter pedal pressure, but you can feel the strength of the clutch. Very quick and precise shifts. First is going to take some getting use to as there is a significantly lower "catch point" but nothing that some practice won't help.

The lighter flywheel is a dream. It feels as if the car may have lost some power in the lower gears but highway sprinting is unreal. The car in 4th gear cruising at ~4000 rpm, stomp on the gas, and watch that rpm meter flyyy.

Assuming the 2 issues above will be resolved, I highly recommend this to any beast owner that's due to replace that P.O.S. Oem clutch. (Mods or no mods)

Guys let me thank you in advance for any info you can provide. As always it is much appreciated.
 

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Jay,

with the sprung hub design the springs in the hub will need some time to loosen up and therefore you should see a reduction in the noise level of the chatter. It will not however go fully away, but it should get better past about 1000 miles.

As for your vibration statement...all i can say is to ask Rob over at UUC about that...or maybe shadowman as they are the two people that seemingly have the most knowledge of this clutch pkg.
 

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Jay, congratulations on the new clutch! I got the same setup about 1 month ago and am very happy with the performance. I easily remedied the vibration upon takeoff by raising my rmp's (slightly) to about 1200-1500 when taking-off. If you tried that with the OEM clutch you would obviously "burn" the clutch, but I don't think it is going to have an adverse affect on the Stage III from UUC.

I can't really tell that the "chatter" has diminished much (if any?) during the time I have had the clutch (1 month). I did an "first impressions" as well as a "1-month update" here

Also, if properly installed the "chatter" goes away when you engage the clutch, and when you are in motion. The only time the "chatter" should be audible is when you are at a dead-stop, with your foot "off" the brake. Let us know if this is the case.

I agree with your initial assessment that the clutch is very street-worthy, and would work well with or without mods. I like knowing that I can now do anything I want to with HP upgrades without having to worry about upgrading the clutch.

Robert
 

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Discussion Starter #4
The chatter only occurs when the car is at a dead stop, as for the brakes, i'm not sure if it stops if i press on the brake, i'll have to check it out. I read your write up and I agree the first to second and the second to third shift have become so much easier, it was sometimes a pain with the OEM setup. But I've had some other weird noises today, when the vibration (almost a jerk like not giving enough gas at point of engagement) normally occurs i've had some kind of weird grinding noise almost. I'm going to have it checked out tommorrow. All the UUC guys are at SEMA so they won't be much help until Monday. Will keep you posted.

Thanks
 

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Kings MotorSport said:
The chatter only occurs when the car is at a dead stop..........
....and I might add, only with the transmission in neutral AND the clutch pedal out. At a dead stop with the clutch pedal depressed (pushed in), rollover noise does not occur, no matter what gear you're in. :rolleyes:
 

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We're baa-aaack! :)

The slight vibration you feel on taking off from a complete stop is a function of the multi-puck design and the material. As it beds in fully, that should smooth out. However, as you may have to do anyway with a lightweight flyhweel, a slight modification of your gas/clutch modulation can eliminate that. I suspect just in the normal course of getting used to it that your engagement style will adjust subconsciously.

The rattle should reduce as well as the sprung-hub springs loosen up. For full effect, it takes 500-1000 miles. Alternately, Amsoil showed us some variations of their ATF specifically to reduce gear rattle. We will be doing some testing over the next feww weeks, I will certainly report to the board if there is any worthwhile development. For M5 results, my own Euro E34 M5 6-speed is the perfect test case; I have experience with many different fluids within that same box, and it has the same general design and rattle characteristics as the box in the E39 M5.
 

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Alternately, Amsoil showed us some variations of their ATF specifically to reduce gear rattle.
Well, there was quite a bit of debate on this board about a year ago over what oil to use in the M5 Getrag trans. Evidently there is a non-metal part or two inside that will fail in the presence of incompatible oil. The damage is supposedly not evident right away, and in fact the car will shift smoother and quieter. But then..... blam. As a result, some of us that originally went to aftermarket fluids went back to the OEM fluid (which retails for about $28/litre btw, and you need 2 litres to fill the trans in our cars). Others have stuck by their aftermarket fluids and so far, so good but maybe it's just a function of the fact that most of our cars are still relatively new. So, I'll be very interested in seeing some long term testing of alternative oils but I'm not holding my breath. I'm convinced of the benefits of the UUC clutch upgrade enough that I will probably go that route when my clutch wears out but unless I get very good evidence, I'm not changing my fluids just to avoid a small bit of noise. :M5launch:
 

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please ,please, don't start the fluid 'thing' again.
N4S , if you've never had a aluminum flywheel'd car you don't know about the noise, when you go to the alum. flywheel any noise is louder than the stock you had, some loud and some fairly acceptable . It depends on each individual box. So the noise becomes annoying and you want to make it quieter asap. If there is no pure evidence of fluids ,and it is all here say they say from opinions from users to product sellers to engineers , you WILL try to make it as quiet as you can, or just live with it. Most would try the fluid change I'll bet! I did, 3 times in the m3 (97 turbo,alum. fly'd with euro 6SPD)

Rob, can you make a note to post back after testing the Amsoil, the rattle is just like I had in the M3, I knew there would be some noise as to be expected but this loud in a M5 not cool. I think the box was quieter with the R/P than with the Redline.
 

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Here is one person who confirms what I have said. The lightened flywheel feels weaker at launch. He says it feels like it lost power in the lower gears with the lightened flywheel. I am not sure if that is a technically correct expression, but it is not reassuring. The lightened flywheel S2 I drove felt absolutely weak on the upshift to 2nd, and it would drop about 300 revs. versus stock on the upshift. That absolutely has to cost time in a street race. The S2 was clearly quicker in gear than my stock M5 though. The S2 was reluctant to break loose in 1st gear starts. It didn't seem as eager as my stock M5 from the drop. It pulled harder afterward though. This was partly due to the huge dip in the torque curve (versus stock) at low to mid r.p.m.s that I have seen in S2 dyno. pulls posted on this board.

Dinan is not the untouchable engineering firm that is claimed. They are innovators and the quality is sound, but their engineering is NOT the absolute best. Look at the Z8 frame debacle, the poor visible contruction of their M5 header, the dip in the S2 power curve, and other stuff. Dinan is good, but highly overrated.
 

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HBRAMSTEDT said:
Here is one person who confirms what I have said. The lightened flywheel feels weaker at launch. He says it feels like it lost power in the lower gears with the lightened flywheel. I am not sure if that is a technically correct expression, but it is not reassuring. The lightened flywheel S2 I drove felt absolutely weak on the upshift to 2nd, and it would drop about 300 revs. versus stock on the upshift. That absolutely has to cost time in a street race. The S2 was clearly quicker in gear than my stock M5 though. The S2 was reluctant to break loose in 1st gear starts. It didn't seem as eager as my stock M5 from the drop. It pulled harder afterward though. This was partly due to the huge dip in the torque curve (versus stock) at low to mid r.p.m.s that I have seen in S2 dyno. pulls posted on this board.

I'll try to give an explanation, but I will preface it with the statement that none of it must be taken out of context or glossed over. If appropriate attention is not given to all that I write below, then none of it should be read.

When you install a lightweigth flywheel, there is no torque loss from the engine. Period, end of story, verify it on a dyno.

A flywheel, by it's very nature, is an energy storage device. It's purpose is to either absorb excess energy from the engine, or average out the energy being put into the transmission, when an imperfect rpm vs. gear/wheelspeed clutch engagement happens.

The energy is stored in it's mass. When you rev your engine, energy is used to move that heavy flywheel... energy that is not put to the wheels. The mass of the flywheel stores that energy by it's motion.

Thus, a lighter flywheel requires less energy to be moved, allowing more of the net total force produced by the engine to go to the wheels, making the car quicker. The mathematics of this are covered on our website here:
http://www.uucmotorwerks.com/flywheel/how_a_lightweight_flywheel_works.htm

But the important question is then, how does this jibe with "real world" experience?

Those who say their car feels quicker with a heavy flywheel are revving the motor above the correct gear/wheelspeed amount, and "dumping" the clutch. The heavy flywheel stored energy, and then transferred it to the transmission/wheels. Technically, during this engagement, the stored energy plus the engine input energy is more than the engine makes alone. The critical thing to realize is that this only holds true during the period of clutch engagement and is a "false torque" sensation.

That "false torque" sensation tricks human perception into thinking the car has more power, when the torque measurement of such an engagement style shows that the "false torque" jump up is immediately followed by a sub-normal torque dip as the heavy flywheel requires more energy input to re-accelerate than the lightweight alternative.

An example of this is quite clear in a dyno graph. This section shows a torque curve, specifically the initial clutch engagement at 2000rpm and up to 3500rpm.



The "false torque" effect of the green line clutch dump is obvious; during, and only during the clutch engagement up to 2500rpm, is the energy that the flywheel has stored being transferred to the drivetrain. After 2500rpm, it uses even more energy to re-accelerate. Contrast this with the red line smooth engagement which has more torque at the wheels everywhere above 2500rpm.

Even though that graph is showing two successive runs on the same car, the point regarding the "false torque" effect of the heavy OE flywheel is exactly the same.

So you see, this is the reason why a lightweight flywheel car will walk away from a heavy flywheel car every time, regardless of how the initial clutch dump may "feel" stronger with the heavy flywheel.

- Rob
 

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"So you see, this is the reason why a lightweight flywheel car will walk away from a heavy flywheel car every time, regardless of how the initial clutch dump may "feel" stronger with the heavy flywheel."-Rob Levinson

Thank you Rob for the graph & explanation.

I to installed the UUC Stage III (6-Puck ceramic) Clutch w/ Lightweight Flywheel about a month ago and I can tell you that the car seems MUCH quicker...through all gears! But, what I couldn't do is expalin it in the technical terms (in addition to the dyno graph!) Rob L. offered in the previous post. I have heard so many people talking about "because of the lightweight flywheel the car won't have the "low" end", "because of the lightweight flywheel you will experience a drop-off in torque from takeoff", etc...

True, most of the people saying that are NOT owners/users of the setup, and are obviously speculating or taking initial "butt-o-meter" impressions from new users. I have the setup, and I can atest (without hesitation or reservation!)to the fact that the car now feels SO MUCH faster than the stock clutch setup that is...well, like a night & day difference :hihi:

As I have previously stated, this clutch setup is awsome! Thanks again to Rob L. and the team at UUC for this much needed, performance enhancing and fine product! :thumbsup:

Robert
 

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Robert of "UUC", question for you please.....

Hey Rob,
I just read your post and it makes total sense to me, but here's my situation and I'd like your opinion please. I have a 2003 model M5 with approx. 7,000 miles on the clock. (its not my daily driving car)
In the next week or so, my local Dinan dealer will be doing the Dinan S2 upgrade mods to the car, except for the lightened fly wheel (stage #1)
After reading your post Im wondering if I should do this mod? I realize that Im asking you whther I should purchase a competitors lightened flywheel and not yours but here's my reason behind it. As of now, my stock clutch is perfect, due to the low mileage and I don't beat down on the clutch. Also, if anything goes wrong with the "initial" first clutch, my car is warrantied until 4yrs/50000 miles so I will be able to get another "free" BMW clutch before having to upgradde to an aftermarket clutch system, which you sell, UUC Stage III (6-Puck ceramic) Clutch. If I was on my second set clutch from BMW and was in need of another clutch or wanted to go with the lightened flywheel setup, I'd surely do your UUC stage III system, but Im not at that point for now. So, if you can provide me with your professional opinion as to whether I should add the Dinan stage # 1 flywheel or simply leave the stock OEM flywheel in place and be part of the S2 or change it to Dinan's flywheel, I'd appreciate it !
Thank you.

Robert :viking:
 

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In my opinion, the fundamental design of the M5 clutch is flawed for two principal reasons:

1) size - 240mm is simply too small for the weight and torque of the car, regardless of material.

2) clutch design - the SAC (Self Adjusting Clutch) mechanism is prone to failure and does not have good feedback even when working properly.

With those two things in mind, replacing your OE setup with any same-design clutch is a waste of money. Especially with the S2 package, you will be needing a new clutch in the near future.

The path of least resistance is simply skipping the clutch swap at all for the moment... drive the S2 setup for awhile, and when you're ready for a new clutch and get the UUC setup, you would get the twin benefits of a refreshed clutch and the lightweight flywheel... not just a repair, but another "hit" of fun!

- Rob
 

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Thanks Rob ! I do agree with your reply post and will probably hold off on the Dinan lightened flywheel, until I need to upgrade EVERYTHING.
One thing, even if I had my OEM clutch replaced by the delaer, it will be free and not as you mentioned. "replacing your OE setup with any same-design clutch is a waste of money." I do however understand your point.
Thanks again Rob. :M5thumbs:
PS Also, I'll be saving money at this time, by not doing the Dinan flywheel. hehehehe............. :hihi:
 

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N4S , if you've never had a aluminum flywheel'd car you don't know about the noise, when you go to the alum. flywheel any noise is louder than the stock you had
You're right, I overlooked that part of the post that said he also went to an aluminum flywheel. I guess the moral of the story is not to go to an aluminum flywheel if you're going with this mod unless you're prepared to put up with a lot of noise.
 

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Discussion Starter #16
UPDATE **

The new clutch has seen about 500 miles now, and I'm going to revise my earlier statements. The lower gear "torque loss" I experienced was due to a busted drive shaft U-joint, which caused a loss of power as the drive train began to spin. The vibration seems to be getting a bit better, but the chatter is still prettyy loud. Hopefully this will improve. Will give a 1000 mile update.
 

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What Rob of UUC said above is only partially true. The flywheel stores energy and redistributes it when the clutch is engaged. While it is true that the lighter flywheel car will out-accelerate a heavy flywheel car in gear with the clutch engaged, it is simply not always true in standing start drag races or in speed contests which span mulitiple gear shifts. Rob fails to account for the drag race scenario where the stored energy of the heavy flywheel releases more energy on 1st gear clutch engagement. This energy is used to get the car in motion. Also, on upshifts, dependent on weight and gear ratio, the heavy flywheel provides "real torque" upon engagement which allows the car sustained acceleration upon clutch engagement. Also, as speed increases and aerodynamic loads go way up over 100 m.p.h. the lighter flywheel is a relative detriment. The advantage to the light flywheel occurs in the lower gears where the change in angular velocity of the crankshaft is greatest.

Of course, the heavy flywheel resists acceleration to a greater degree while in gear. All I am saying is that he left part of the analysis out.

The other common myth is that lighter flywheels always result in better acceleration. This is simply not true. For a heavy car like the M5, light flywheels provide relatively less of a performance advantage.

The analysis where the light flywheel costs time is when a heavy car has to transition to the next gear ratio and the mass of the flywheel is not sufficient to keep the r.p.m.s up. The result is that the revs. drop and the engine has to regain those revs. Time is lost in this situation.

I have not seen a lightened flywheel M5 post strong drag times on this board to date. The fastest M5s here all had standard flywheels.
 

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HBRAMSTEDT said:
........the stored energy of the heavy flywheel releases more energy on 1st gear clutch engagement. This energy is used to get the car in motion.
This is true, but "more energy" can not be exploited in all cases. Kinetic flywheel energy is paramount for underpowered cars with featherweight reciprocating assemblies & low torque motors that do not produce sufficient power on-tap to churn tires at will from a standstill. Many econobox racers leave the line at 6K! IMO, the E39 4.4L and 5L V8 motors have more than enough power to "get the car in motion" without adding large doses of stored flywheel kinetic energy.

Anyway, it's important to note that launching methods will determine whether you exploit your flywheel kinetic energy or not. I launch at part thottle under 2K RPM by quickly releasing the clutch and then stomp & "walk out of the hole" at WOT, using 100% motor torque & almost 0% stored energy. This allows me to leave two faint black stripes on the road as the motor/flywheel accelerates, without uncontrolled wheelspin. Under these conditions, a heavy flywheel actually impedes acceleration. Everybody's launch habits vary..which is one reason why some see 12K mi per OEM clutch and other's see 70K+ (lol).

Here's a key point to consider:

When exploiting flywheel KE, by definition, the engine & flywheel RPM must be DROPPING. At launch, this can only occur during periods of clutch slip or wheelspin.

I prefer to minimize slip and wheelspin. In my experience neither condition is very helpful, if you have a tractible V8 powerplant.

If you're rev'ing the motor to 4K+ like someone wringing out an asian econobox and dumping the clutch, then you're using tons of flywheel KE to your advantage. Frankly I think there's more than enough raw V8 power on-tap in the M5 to reach the limit of adhesion (without lots of KE) to post optimal 60' acceleration times. This is precisely why I do not want to install deeper gears in my car. If I had a 3L powerplant or 14" wide Mickey Thompson drag radials & trying to pull wheelies, I'd feel different.
 

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Has anyone got a sound clip of the Clutch clatter? I've had the UUC Stg3 kit fitted since Apr04, and performance'wise am very happy with it, under repeatedly hard driving, hasn't let me down once... which is more important that abit of "dieselly sound".

does take alittle while getting used to though, as the "bite" point is quite high, but its a trade off.
 

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HBRAMSTEDT said:
What Rob of UUC said above is only partially true. The flywheel stores energy and redistributes it when the clutch is engaged. While it is true that the lighter flywheel car will out-accelerate a heavy flywheel car in gear with the clutch engaged, it is simply not always true in standing start drag races or in speed contests which span mulitiple gear shifts. Rob fails to account for the drag race scenario where the stored energy of the heavy flywheel releases more energy on 1st gear clutch engagement. This energy is used to get the car in motion. Also, on upshifts, dependent on weight and gear ratio, the heavy flywheel provides "real torque" upon engagement which allows the car sustained acceleration upon clutch engagement. Also, as speed increases and aerodynamic loads go way up over 100 m.p.h. the lighter flywheel is a relative detriment. The advantage to the light flywheel occurs in the lower gears where the change in angular velocity of the crankshaft is greatest.

Of course, the heavy flywheel resists acceleration to a greater degree while in gear. All I am saying is that he left part of the analysis out.

Actually, my analysis was completely accurate, nothing left out.

There is some substantial testing that confirms what I wrote...

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

- Rob
 
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