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post #1 of 25 (permalink) Old Sep 28th, 2009, 12:52 pm Thread Starter
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Quieter Clutches

Ducati Clutch Basics

The Ducati dry clutch is famous for it’s unique noise that makes it desireable to some but an annoyance to others. The reason that they’re noisy is that each time you shift, the edges of the friction plates hammer the fingers of the clutch basket, causing each to deform, and making the gap between them to get larger, causing higher impact forces (the next time), and so on, causing a louder rattling noise each time the clutch is disengaged. So, they get louder and louder until the plates and basket are replaced.

The noise doesn’t necessarily mean that your clutch is worn out. A clutch is considered worn out when the thickness of the friction material on one or more friction plates exceeds the minimum allowable. It’s recommended that you replace a 3mm (new) friction plate when it reaches it’s service limit of 2.8mm, and replace a 2.5mm friction plate when it reaches 2.3mm.

When the plates wear, the plate stack height is reduced so when the stack height wears 0.5mm, you can replace one flat steel plate with a one 0.5mm thicker to recover the correct stack height. At 1.0mm wear repeat for a second flat plate. At 1.4mm wear you’ll want to replace the friction plates. This is the time to replace the basket if you want to quiet your clutch.

Ducati Clutches need to be stacked to 38mm plus (+) or minus (-) 2mm.* The reason that maintaining the overall stack height is important is that the force pushing the plates together comes from the preload of the clutch springs. The higher the stack height, the higher the preload. Also for a given stack height, the more springs the higher the force pushing the plates together. Not enough spring preload, not enough springs, or not enough friction material and your clutch will slip.

The standard test for a slipping clutch is to check while accelerating in top gear.


Quiet Clutch Mod

It’s been sugested that adding a plate at the bottom of the stack will reduce clutch noise. This plate is not an addition to the existing stack, the stack height has to be maintained. This is a rearrangement of plates in the stack.

The idea here is to move the friction plates to a new location in the stack so that they no longer are alligned with the notches in the basket (notches that they caused previously.) This in turn reduces the tab-to basket clearances for the friction plates so you get less noise.



The arrangement of plates in the stack, the number of plates, and the thickness of plates vary from model to model, but the one feature that all arrangents have in common is stack height. Here’s some examples:


748, 916, 996 (From the Haynes Manual)
7 friction plates
1 convex plate


2.0mm flat plate
2.0mm*flat plate
3.0mm friction plate
1.5mm convex plate (convex side facing outwards)
3.0mm friction plate
2.0mm*flat plate
3.0mm friction plate
2.0mm flat plate
3.0mm friction plate
2.0mm*flat plate
3.0mm friction plate
2.0mm flat plate
3.0mm friction plate
2.0mm flat plate
3.0mm friction plate
2.0mm flat plate
pressure plate (line up marks)
38.5mm Total


916SP, 916SPS, 996S, 996SPS
8 (thinner) friction plates
2 convex plates


2.0mm flat plate
1.5mm convex plate (convex side facing outwards)
2.5mm friction plate
1.5mm*flat plate
2.5mm friction plate
2.0mm flat plate
2.5mm friction plate
2.0mm*flat plate
2.5mm friction plate
2.0mm flat plate
2.5mm friction plate
2.0mm*flat plate
2.5mm friction plate
2.0mm flat plate
2.5mm friction plate
1.5mm flat plate
2.5mm friction plate
1.5mm convex plate (convex side facing inwards)
pressure plate (line up marks)
38mm Total


998 (From the Ducati Service Manual)
6 friction plates
1 convex plate


2.0mm flat plate
1.5mm convex plate (convex side facing outwards)
2.5mm*flat plate
1.5mm flat plate
3.0mm friction plate
2.0mm*flat plate
3.0mm friction plate
2.0mm*flat plate
3.0mm friction plate
2.0mm flat plate
3.0mm friction plate
2.0mm*flat plate
3.0mm friction plate
2.0mm flat plate
3.0mm friction plate
1.5mm flat plate
2.5mm*flat plate
1.5mm convex plate (convex side facing outwards)
pressure plate (line up marks)
38mm Total

Of course shifting the plates around to reduce plate-to-basket clearances is only a temporary fix until the plates hammer-out new and bigger clearances.

More Lasting Solutions

There has been some innovation to try to address the durability issue associated with the plates impacting and notching the basket.

For example, STM and Sigma (UK) has tried to overcome this problem by increasing the number of tabs on each plate (and the number of basket fingers) from the stock 12 to 48 tabs. The intended result is to distribute the impact loads over a larger tab-basket contact area (lower psi) to reduce notching to the clutch basket fingers and mushrooming of the plate tabs. Only STM and Sigma offer a 48-tab clutch pack, however.

Nichols Manufacturing designed their CNC-machined aluminum basket with wider basket fingers that results in larger finger contact area and consequently lower impact stresses, particularly when combined with their Barnett aluminum clutch pack where extra care has been taken to initially minimize gaps. Basket: $299, clutch plates: $139.

Another option is a Barnett aluminum basket with stainless steel inserts to protect the basket fingers. About $225.

Keep in mind that when you mix steel and aluminum, the softer metal deforms preferentially and clearance gaps suffer, more than for steel-to-steel. So if you have a steel basket, stick with steel plates.


Last edited by Shazaam; Sep 28th, 2009 at 1:01 pm.
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post #2 of 25 (permalink) Old Sep 28th, 2009, 2:02 pm
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Good write up shazaam. The quiet clutch mod that I have used uses 1 or 2 friction plates in the bottom of the stack so that they sits against the bottom of the slots in the basket rather than the steel plates sitting against the bottom of the splines in the hub.

This prevents plates from rattling by having the pack loaded against the outer basket rather than the inner hub when disengaged preventing the rattle.

This is easier to do on the older sqaure bottomed slot steel baskets like the 90's 900 SS rather than the aluminium radiused bottomed baskets.

Less rattling means longer life for the tabs, meaning you could wearthe plate friction material out before the basket gets heavy slots.

There could theoreticaly be additional load placed on the hub bearing but haven't heard of anyone having one fail.

This is different from the quiet mod you have mentioned.


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post #3 of 25 (permalink) Old Sep 28th, 2009, 11:53 pm
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Quote:
Originally Posted by Corse1 View Post
Good write up shazaam. The quiet clutch mod that I have used uses 1 or 2 friction plates in the bottom of the stack so that they sits against the bottom of the slots in the basket rather than the steel plates sitting against the bottom of the splines in the hub.

This prevents plates from rattling by having the pack loaded against the outer basket rather than the inner hub when disengaged preventing the rattle.

This is easier to do on the older sqaure bottomed slot steel baskets like the 90's 900 SS rather than the aluminium radiused bottomed baskets.

Less rattling means longer life for the tabs, meaning you could wearthe plate friction material out before the basket gets heavy slots.

There could theoreticaly be additional load placed on the hub bearing but haven't heard of anyone having one fail.

This is different from the quiet mod you have mentioned.
+1, this is not the same quiet mod that was discussed in the other thread
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post #4 of 25 (permalink) Old Sep 29th, 2009, 7:26 am
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I agree with Corse. The original quiet clutch mod reducers the space for the plates to rattle by adding two steel plates at the back rather than as suggested in the original post that it merely moves the plates so that they vibrate or rub on a different part of the basket. I did the quiet clutch mod and am well impressed with it as it does not take away completely the dry clutch rattle that we all love so much when disengaged or in neutral, it rather just reducers the clatter a tad..

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post #5 of 25 (permalink) Old Oct 7th, 2009, 1:48 pm
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why is it that ducati designed the cluctches this way however?
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post #6 of 25 (permalink) Old Nov 18th, 2009, 2:46 am
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Originally Posted by Brendon857 View Post
why is it that ducati designed the clutch this way however?
Being dry, the clutch doesn't loose torque spinning in a fluid. I read once, and thought it well said "Ducati designed the bike, then thought about the rider. Other bikes are designed for the rider, then thought about the bike"

Quote:
Originally Posted by Shazaam View Post
The reason that they’re noisy is that each time you shift, the edges of the friction plates hammer the fingers of the clutch basket, causing each to deform, and making the gap between them to get larger, causing higher impact forces (the next time), and so on, causing a louder rattling noise each time the clutch is disengaged. So, they get louder and louder until the plates and basket are replaced.
Shazaam, great write up!

In neutral with the clutch engaged the plates are banging away against the basket in the torque ripple of the 2 cylinders. Could this also be a contributer to the notches in the basket?
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post #7 of 25 (permalink) Old Dec 2nd, 2009, 1:11 pm
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I received a clutch pack but it didn't contain a convex plate. Do I need to find a replacement?

ps. It's for a '97 748bip

pps. The old plates were all discarded.

Thanks in advance and thanks for the great write up.
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post #8 of 25 (permalink) Old Dec 15th, 2009, 3:58 pm
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Quote:
Originally Posted by Shazaam View Post

When the plates wear, the plate stack height is reduced so when the stack height wears 0.5mm, you can replace one flat steel plate with a one 0.5mm thicker to recover the correct stack height. At 1.0mm wear repeat for a second flat plate. At 1.4mm wear you’ll want to replace the friction plates. This is the time to replace the basket if you want to quiet your clutch.
Will this work for a wet clutch as well? Also, instead of replacing a .5 with a 1.0, could you just add an extra .5mm plate? My second clutch is starting to slip, but I still have my original clutch pack to steal plates from.
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post #9 of 25 (permalink) Old Dec 30th, 2009, 1:09 am
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see questions above. Opening up the clutch on Sunday.
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post #10 of 25 (permalink) Old Dec 30th, 2009, 2:17 am
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Originally Posted by snlsmith View Post
Will this work for a wet clutch as well? Also, instead of replacing a .5 with a 1.0, could you just add an extra .5mm plate? My second clutch is starting to slip, but I still have my original clutch pack to steal plates from.
Plates are either 1.5mm or 2.0mm, not 0.5mm and 1.0mm

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