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Clutch Disc Options
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11378
Location: PacNW

PostPosted: Tue Mar 23, 2010 12:46 am    Post subject: Clutch Disc Options Reply with quote

I'm growing concerned about Sachs (it's a sachsual problem).

My buddy pulled the motor from his race car following a clutch failure, and found that several rivets had failed and a large piece of friction material had come loose. He related that many 944 Spec guys had seen this failure over the last several years. . .clearly a manufacturing defect.

Needless to say, I am not eager to install a similar disc from the same manufacturer. What other reasonable options are there?

*I'm aware of the Bronco option. . .I am curious about discs actually intended for the 931*
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Toofah King Bad

  • Red (1987 924S) - Pro44/Spec944
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fiat22turbo  



Joined: 18 Jan 2006
Posts: 4040
Location: Portland, OR

PostPosted: Tue Mar 23, 2010 3:04 am    Post subject: Reply with quote

Contact Clutchnet. They make everything in house and their clutches survive 400+hp turbo cars and their slipping drag launches (keep in mind the stock engines put out 175hp and getting a FWD car to leave the line with a 1.8 second 60-ft is impressive)

Centerforce used to be a go to for clutches until it was discovered that they were merely reboxing Sachs clutch discs with their own PP. Not sure if they still do. Clutchnet came to the rescue and can likely come up with something for us, if they don't already have something ready to go.

Just checked their site, they have nearly any configuration you'd like.
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1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)
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ic932  



Joined: 11 Feb 2005
Posts: 1104
Location: UK

PostPosted: Tue Mar 23, 2010 3:17 am    Post subject: Reply with quote

I wasn't aware that there were any other options "intended" for the 931?

However, if you are lucky enough to source a late 82' (ROW at least) flywheel then that opens up the 944 aftermarket world. The reason being this flywheel is use in conjuction with the rubber centred type clutch discs.

Well worth considering if you run a dogleg box. I read somewhere that this was Porsche's answer to the syncro problem?

BTW, rubber centred clutches get a bad rap IMO. Bad owners who think wear parts should live forever!

If you are paranoid get your new disc re-riveted...
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Shurick  



Joined: 15 May 2005
Posts: 507
Location: Russia, Moscow.

PostPosted: Tue Mar 23, 2010 6:06 pm    Post subject: Reply with quote

Had a ClutchNet disk in my 931. It was a pain to drive and death to transmission mounts.
Now I have a SPEC (stage 2) disk and pressure plate installed but haven't tested it yet.
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WBR, Shurick
'79 931 -- intercooled K26-3060-6.10 turbo @ 1.2 bar, EFI+EDIS, 951S brakes, stripped interior, 951 look.
'86 924S -- R.I.P.
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fiat22turbo  



Joined: 18 Jan 2006
Posts: 4040
Location: Portland, OR

PostPosted: Tue Mar 23, 2010 11:25 pm    Post subject: Reply with quote

Can you go look at their site and tell us which disc you had?

Sounds like a 3 or 4 pick race clutch. Which pressure plate did you use with it?
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1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)
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peterld  



Joined: 10 Dec 2006
Posts: 771
Location: Noosa Heads QLD Australia

PostPosted: Wed Mar 24, 2010 12:47 am    Post subject: Reply with quote

Rubber centred clutches and also flywheels are a fact of life in modern cars - they seamingly make gearchanges lighter and easier and stop the gear chatter, particularly in neutral. However they have a history of failing when the rubber starts to disintegrate through misuse, oil contamination, etc.
Porsche used them in 924s,then 944s and eventually in 911s. There are many documented horror stories out there.
Having said that, my track car still retains it's rubber centered clutch disc. This is still the original clutch disc!!!! Every time the motor comes out I check it and consider changing to something else, but always the disc still has plenty of life in it and the rubber is not compromised. So I chance it one more time. One day I guess the 30yo clutch will fail and leave me stuck in gear.
If memory serves me correctly, the 911/915 clutch is supposed to fit 931s, however buying off the rack is never as good as having a clutch rebuilt or made to your specs by a reputable local clutch guy - if you have one handy. One of the few automotive trades which hasn't yet disappeared and isn't too technically/digitally/electronically challenged if you discount all the trickery of modern twin clutch semi auto gearboxes.
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ideola  



Joined: 01 Oct 2004
Posts: 15501
Location: Woodstock IL

PostPosted: Wed Mar 24, 2010 2:59 am    Post subject: Reply with quote

I have been thru every Porsche listing on ClutchNet's site, and they do not carry a disc that will work for our cars...they either have the wrong spline diameter, spline count, or outer diameter. I contacted them recently about doing something custom and never even got the courtesy of a return call.

Centerforce and Spec are the only companies I am aware of that advertise an aftermarket option; Centerforce have a bad reputation, and Spec are SPENDY, and apparently only available as a complete kit (pressure plate, clutch disc and throwout bearing), although I've not yet inquired about purchasing a disc only.

The 915 pressure plates (the full iron and hybrid alloy-iron) are direct fit replacement and purportedly offer 2x clamping force over the stock 931 cover. I seem to remember bass gt posting that the all alloy version requires some mods, but can't recall the details ATM.
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McGyver  



Joined: 24 Feb 2009
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Location: Jelenia Gora - Poland

PostPosted: Wed Mar 24, 2010 6:26 am    Post subject: Reply with quote

As I remember Sachs made two types clutch discs for 931:
931 116 011 04 - spring damped
944 116 012 08 - rubber damped

So if rubber takes more damage why don't use that plate with springs? It's more compatibile with sports cars and stronger, and dont so sensitive than rubber one. Maybe changeing gears can be felt much stronger but it's sports car
I have one 931 clutch with springs as spare and something in my car I don't really know which type but I check this when I swap to 931 engine again.
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ideola  



Joined: 01 Oct 2004
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Location: Woodstock IL

PostPosted: Wed Mar 24, 2010 6:30 am    Post subject: Reply with quote

The rubber and spring types aren't interchangeable as the flywheel changes as well.
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McGyver  



Joined: 24 Feb 2009
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PostPosted: Wed Mar 24, 2010 6:58 am    Post subject: Reply with quote

You right. I didn't noticed that before. Maybe someone can post some photos what are differences between this two types of flywheels? If I can get mine from some box I can make photo session of that spring type clutch
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931 82' - 5000km after full engine rebuild

SOLD: 924 81' N/A- with turbo gearbox "dogleg" - great but mysterious car
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ic932  



Joined: 11 Feb 2005
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Location: UK

PostPosted: Wed Mar 24, 2010 7:39 am    Post subject: Reply with quote

Michal, Porsche made a descision to use a rubber-centred clutch sometime in 82'. From what I read many years ago (I can't provide a ref.) they introduced this disc as a direct responce to premature gearbox syncro wear. Strengh is all well and good but if the longevity of the "weakest link" (syncros.. if this is indeed the case) , then what good would a clutch be if it contributed to this premature wea,r no matter how impressive it's clamping force?
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11378
Location: PacNW

PostPosted: Wed Mar 24, 2010 4:10 pm    Post subject: Reply with quote

ideola wrote:
I have been thru every Porsche listing on ClutchNet's site, and they do not carry a disc that will work for our cars....


Was there a Bronco disc listed?


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Toofah King Bad

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daniel  



Joined: 18 Jun 2009
Posts: 620
Location: Sydney, Australia

PostPosted: Wed Mar 24, 2010 5:29 pm    Post subject: Reply with quote

My 944 had a rubber centre clutch, failed shortly after buying it. I replaced with the sachs recomended replacment which is a normal spring centre clutch. No dramas at all

Daniel
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Shurick  



Joined: 15 May 2005
Posts: 507
Location: Russia, Moscow.

PostPosted: Wed Mar 24, 2010 10:30 pm    Post subject: Reply with quote

fiat22turbo wrote:
Can you go look at their site and tell us which disc you had?

Sounds like a 3 or 4 pick race clutch. Which pressure plate did you use with it?

It was 6 pick with spring hub. I used it with S1 stock pressure plate and flywheel.
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WBR, Shurick
'79 931 -- intercooled K26-3060-6.10 turbo @ 1.2 bar, EFI+EDIS, 951S brakes, stripped interior, 951 look.
'86 924S -- R.I.P.
https://www.instagram.com/ru_pacecar/
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Smoothie  



Joined: 01 Jan 2003
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Location: DE (the one near MD, PA, NJ)

PostPosted: Wed Mar 24, 2010 10:57 pm    Post subject: Reply with quote

More on the different flywheels here - http://www.924board.org/viewtopic.php?t=21820
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