[RS Barn]

The main reason not to use 951 Disc is spring failure problems. My 951Turbo Cup spit them out and destroyed everything.

I'm driving at Mosport in picture

Pete

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[flash]

i'm not terribly surprised - the spring cover plates are the less than desireable "open" design, and the whole thing is only held together by 3 rivets - that leaves a lot of room for movement, and in turn, failure



the springs are pretty soft too, which can lead to coil bind in a higher torque engine, and that results in chatter - really surprised it was a 930 disk - must be a really light set of crank, pistons and flywheel



i feel your pain pete - that HAS to be a drag - i know when i fragged my 25k mile stock disk, it pretty much spoiled my day - of all the things i anticipated going wrong on that track that day, the clutch disk was not one of them

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[kramermic]

Well, being a street car and not seeing any track time, it should hold up fine.



It should certainly hold up better than the stock disk..... This was never an option for us and I'm surprised fidanza would recommend this.



After your 951 cup clutch came apart, what did you go to?

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[flash]

i'm confused - maybe i missed something - surprised fidanza would recommend what? they only recommend the stock disk because of the issues they found when they tried all other porsche disks - the stock disk is all there was for them to recommend, but even they will tell you that clutch life is shortened with a light flywheel



as for holding up, perhaps - perhaps not - time will tell - i hope it works out for you



i think it all depends on a lot of factors - the lightweight flywheel more than doubles the impact load on the clutch disk - in 25 years of playing with light flywheels, i don't think i have ever gotten more than 40k out of a clutch disk with a light flywheel, aluminum or otherwise - this situation is going to be hard on a disk that is already known to fail - if the cup cars were fragging them, you can be sure that an engine with more pulse impact, and crank/piston mass is going to



that is exactly why, besides resolving the interference issues, we have spent so much time and energy coming up with a disk that is a lot stronger and with better friction material than anything out there



the fifth (and hopefully last) prototype goes in today

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[PorscheDude]

I for one, am pulling for ya!



Between Pete and youself, the unique 968 aftermarket has more support and useful performance mods than at any other time in the history of the car.

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[kramermic]

951 clutch disks known to fail??? Spring hub coming apart? I've never heard of this being an issue until RS mentioned it. I don't doubt that he had a problem....but common? I don't think so.? Especially not on a street car that doesn't get abused on the track like a 951 cup car. How many spring hubs do you see coming apart on the 951 street cars? My dad opened his shop about 25 or so years ago and has never seen one of these clutches come apart the way described above. Of course it can happen, but to say it's a common problem and that it's a reason not to use it seems ridiculous. The way my clutch is set up now is essentially the same as a 951 street car with a lwfw. 930 clutch disks have the same open spring design and hold up to way more abuse than a 968 could put out.



As far as fidanza's recommendation, you're correct. They can't recommend anything but this. Putting a solid flywheel and a clutch disk w/o a spring hub into a street car doesn't make sense to me. Forget the clutch, I would be more worried about other parts taking that added stress.



Flash, you have put in a lot of time into finding another solution and I hope it works out well for you and perhaps you can pass that along to other folks that aren't interested or able to create the solution. I have just over 1000 miles on my new set up and couldn't be happier. I hope your system works as well.

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[flash]

well, i didn't say it was common - i said it was known to fail - i have heard of it happening, besides pete's experience



by the way, according to paragon, if you look closely - that disk IS a 930 disk



on that point, it's not just the horsepower that is the issue- a 4 cylinder engine produces a lot more pulse than a 6 cylinder - balance is also an issue - we know our engines are already "lumpy" - the mass of the reciprocating parts also plays into the pulse impact - the bottom line is that our engines will put more strain on a clutch disk than a 930 engine



any performance clutch manufacturer will tell you that open springs are less than desirable - the fact that it only has 3 rivets REALLY makes me nervous - combined, i am pretty certain i would frag it on my car - i destroyed the stock disk, which was still full thickness (the small bits that were left) and only 25k on it



i really hope your disk works for you, and lasts, but i am skeptical of the springs and the rivets - the shaving of the bolts bothers me too - the chatter you have indicates a problem somewhere, though i am not certain where it is - was everything new and balanced?



i agree about the desire to have a spring hub, and for the same reasons - that's why we are taking such pains to design a good one - this will be plug and play or not at all

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[spectre996]

Well Flash, We are all anxiously awaiting the results of your 5th prototype. How is it going?

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[flash]

will have definitive info today - i'm at pete's shop today

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[spectre996]

[quote name='flash' post='44629' date='Dec 14 2007, 09:43 AM']will have definitive info today - i'm at pete's shop today[/quote]

Good! Then you can also finally post some pictures of the new cabs right? <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" />

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[flash]

lol - will do that of this one as soon as i get her home and detail it a bit



update on the disk - today i went for a ride in the car that has the fifth prototype - pleased with the result - very definite decrease in the noise - extremely limited rpm range of it now - really limited to 1st and 2nd, and MUCH less of it in those gears - gotta be honest - not completely gone though - if i had to quantify it, i'd say 50% less in 1st and 2nd, and 80% less elsewhere (you really have to try to make it happen in other gears) - all in all a good trade-off for the performance, but if noises really bug you, this still might not be enough - probably as good as it will get though, and be strong enough to hold up - none of the porsche disks will do it - there are enough dead ones lying around to prove that



upside - MUCH better disk - engagement is smoother - disk is MUCH stronger - springs are encapsulated (so none of the failure issues of the 930/951 disk) - more rivets - fully bonded and riveted friction material - steel backing plate - improved friction material - shock impact reduced, which will increase tranny life expectancy



i think you'd have to be a special kind of idiot to frag this disk - lol - even i should have a very hard time blowing it up

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[Cloud9...68]

Thanks for the update - we all tremendously appreciate all the hard work you've done to keep improving our cars. One question, though you've probably already stated it somewhere in this thread - I assume that since your car has the Fidanza flywheel, the development of the spring-centered disk has all been done with the Fidanza, and not the RS Barn. Could your new disk be used with either flywheel? The RS Barn is a few pounds heavier, so I imagine would cut down on what's left of the noise. But it is more expensive, and from a pure performance standpoint, the Fidanza should have the edge due to its lighter weight. If the disk worked with either flywheel, it would give people the flexibility to choose among the trade-offs. But even if it just works with the Fidanza, it sounds like you've come up with a great solution, and a viable alternative to the DMF for those who don't drive their cars much in stop-and-go traffic (that definitely describes me <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> )

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[Anchorman]

Hey, Flash - excellent progress.



Too bad you hadn't told me you were "here" - we could have gotten together. (Actually not, though - because I'm not "here", I'm on a two-week business trip and I'm writing this from my hotel room in Taipei. Oh, well.)



Do I also gather that you found your second cab? If so, I'd missed that - congrats. Can't wait to see how that one evolves (yeah, I know, it's not yours, it won't fall victim the same way, yada, yada, yada).

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[spectre996]

[quote name='spectre996' post='44632' date='Dec 14 2007, 10:07 AM']Good! Then you can also finally post some pictures of the new cabs right? <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" />[/quote]



I think I may have mispoke in my earlier post. I'm pretty sure he has only found one so far. The one that is currently at the Barn. I'm sure he'll comfirm or deny it himself though.

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