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Old 02-15-2010, 03:36 PM   #1
hasenwerk OP
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180mm clutch disk BMW vs VW

OK... RB Racing's sprung clutches are fictional from what I have gathered from other riders. Too bad, they seemed like a nice idea! Then I started to Google 180mm clutches and kept on coming up with early 60s Volkswagen Beetle stuff... so... $48 including postage later I have a new 180mm sprung clutch disc from a Volkswagen Beetle.


Worn out R1100 GS on left, new VW Beetle on right

Both are 180mm wide. Both fit on the same on the GS's input shaft. The only difference is that the VW clutch is thicker, 9mm vs 5mm remaining on my BMW disc - I have no new BMW clutch to use as a reference - what are they supposed to measure?

The only difference is the thickness of the center hub. BMW = 20mm and the VW is 25mm - The BMW could easily be machined down by 5mm and be identical. I have yet to assemble to see if the springs get in the way of anything... but there are unsprung versions of this clutch as well.

So... the only other "real" aftermarket 180mm clutch is the Touratech four puck disc at $650 and change! Which got me to thinking about getting some ceramic four puck clutches made up... there are a few places that make custom VW clutches around...

Questions I have for the group would be:

- How thick is the stock R1100 GS clutch?
- How thick is the Touratech four puck ceramic clutch?

I am sure I could get ceramic clutches built for a LOT less money than Touratech!!
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Old 02-15-2010, 03:48 PM   #2
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New clutch plate thickness is approx 6.4mm - be interesting to see if the center plate springs miss the diaphram spring and that you can disengage the clutch. Good luck.
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Old 02-15-2010, 03:51 PM   #3
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even if the sprung hub doesnt play out, you could always drill out the rivets, and replace your friction material for the $48 cost.

great thread!
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Old 02-15-2010, 03:52 PM   #4
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Old 02-15-2010, 04:25 PM   #5
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If this doesn't work out, you could get the ceramic clutch that Touratech sells directly from the source in South Africa for about half the price:

http://www.advrider.com/forums/showthread.php?t=335934
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Old 02-15-2010, 05:17 PM   #6
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You know the input shaft has a spring load shock absorber, right? Wouldn't that work like a sprung clutch hub?
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Old 02-15-2010, 06:24 PM   #7
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Sounds like a plan, my bike has the TT clutch,though it was fitted before I owned the bike, I believe that the TT one is also thicker than stock, which is why spacing washers are used to accommodate the extra thickness, the paperwork from TT suggests that these can be removed once the clutch has worn down.
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Old 02-15-2010, 06:53 PM   #8
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Looks like a great concept, Im looking forward to your results. clutch prices seem kinda crazy these days. I'll be watching this one....
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Old 02-15-2010, 06:53 PM   #9
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Quote:
Originally Posted by hasenwerk
...early 60s Volkswagen Beetle stuff... $48 including postage

Both are 180mm wide. Both fit on the same on the GS's input shaft.

...there are unsprung versions of this clutch as well.
 Someone was eventually going to discover this and try your experiment.

Re the fiction material thickness, space out the pressure plate to make up the difference. As Stewart says, Touratech uses spacers for their ceramic clutch.



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Old 02-15-2010, 07:01 PM   #10
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Quote:
Originally Posted by Anorak

You know the input shaft has a spring load shock absorber, right? Wouldn't that work like a sprung clutch hub?
Sure would. There might be a difference in spring rate or travel. Moot point though, since the Volkswagen disk is available in an unsprung version.

On a related note, does the Vee Dub disk have a compression spring between the friction material?



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Old 02-15-2010, 07:10 PM   #11
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Old 02-15-2010, 07:19 PM   #12
def
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I worked at an independent VW shop in the 60s and changed many a VW clutch. Also, if the VW owner would spring for the extra $s, we would install a Porsche disk in the VW rendering the clutch almost industructible. BTW, I never observed worn clutch or transaxle input splines in all the clutches I replaced.

Also, I used to race with a fellow tech to see who could get the VW engine out and on the floor the fastest.........he won...14 minutes. A clutch disk swap was under an hour.
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Old 02-15-2010, 08:10 PM   #13
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The motor R+R is always big fun at a Bug In.


Spline wear is due to a couple of things. The two issues work independently, and also amplify the other. One issue is the drive disk isn't centered on the disk spline. I don't mean that the clutch splines overhang the gearbox splines, which they do by a small amount but that isn't the problem. But that the clutch disk isn't centered on the clutch hub, it's offset to one side. The other issue is the gearbox shaft is unsupported at the crankshaft end, and supports the weight of the clutch disk without the benefit of a pilot bearing.

The offset-from-the-center drive force causes the clutch spline to deflect radially on the gearbox spline. (Maybe rotates on it's axis is a better visual, like how the Earth is tilted on its axis.) That deflection happens during the shock accelerations of gear changes, when the clutch disk rapidly changes velocity as the gearbox ratios change. The clutch hub momentarily 'tilts on the splines' if you will, and that wears away at the gearbox splines. If the drive force were centered on the spline that would not happen.

The other issue is when the clutch plate is retracted, the unsupported gearbox shaft falls against the weight of the clutch disk. This movement causes a slight misalignment between the clutch disk and pressure plate which 'tilts the splines' just as above. The effect is also the same, it slowly wears out the clutch splines.



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Old 02-15-2010, 08:28 PM   #14
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It's looking like an unsprung VW clutch with a machined down center hub would be the ticket!

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Old 02-15-2010, 08:52 PM   #15
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i found a clutch maker (usually makes truck clutches) that is making me a custom clutch for my R1200gs. he is using kevlar instead of ceramic. it engages way softer but holds strong. my trucking buddy said his all kevlar clutch was the smoothest and best clutch he ever had. if the custom clutch works out i'm sure i could get him to make some more. all me watching this thread with interest
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