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Discussion Starter · #1 ·
Quick question regarding the order/position of the convex plate in the clutch stack: I pulled apart the clutch on my '00 996 and found 8 friction plates with alternating steel plates as expected... However, the convex plate was narrower than the rest of the steel plates (in width also, not just height) and was all the way at the bottom of the stack. In other words, instead of starting with two flat steel plates, the pack started with the narrow convex steel and then a normal steel. This is the first time I've had the clutch apart on this bike, so I don't know if the narrow convex plate in that position is normal or not.

My new setup has only 7 friction plates and did not come with a convex plate but rather a flat 1.5mm. Not sure how to put the new one together, specifically with regards to the narrow convex plate from the old pack - do I need it and where should it go, or is the only real criteria getting the stack height to 38mm? Any advice would be much appreciated!
 

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I don't use convex plates, don't see the point and they cause the clutch to drag making finding neutral difficult.

I just set the stack 38mm or less (I find neutral selection is better at a little under but never more than 38mm) with all flat plates, be they 2mm or 1.5mm.
 

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The main concern is the correct stack height necessary to preload the springs in order to prevent slippage.

The stack height can be achieved with seven 3 mm friction plates or eight 2.5 mm friction plates. For example:

748, 916, 996 (From the Haynes Manual)
7 (thicker 3.0 mm) friction plates
1 convex plate


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

916SP, 916SPS, 996S, 996SPS (OEM)
8 (thinner 2.5 mm) friction plates
2 convex plates


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


If you prefer your clutch engagement to be an immediate "now", you can use one or more flat plates instead of curved spring plates in the stack.

If you prefer a smoother clutch engagement with minimum "judder" upon launch, then use spring plates in the stack. If you check the recommended clutch stacking order for a number of Ducati models, the number, position and orientation of the spring plate doesn't appear to be consistent or even important.
 

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A convex plate doesn't make full surface contact with either friction plate against it, also when at maximum thickness it doesn't release as cleanly as a flat plate.

Therefore, IMO they are an abomination, serving no purpose whatever other than to make the clutch slip, not engage properly and unevenly wear 2 of the friction plates.
 

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A convex plate doesn't make full surface contact with either friction plate against it ...
Keep in mind that the frictional force that develops between two surfaces is a function of the force pushing the the surfaces together, and the coefficient of friction between the steel plate and the friction material. Contrary to one's intuition, it's independent of the surface area in contact — doesn't make a difference.
 

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Keep in mind that the frictional force that develops between two surfaces is a function of the force pushing the the surfaces together, and the coefficient of friction between the steel plate and the friction material. Contrary to one's intuition, it's independent of the surface area in contact — doesn't make a difference.
Makes a difference to the way they work.

I replaced the plates in my 916 and used a convex plate to make up the thickness, at 38mm I couldn't get neutral with the engine running. I replaced the 1.5mm convex plate with a 1.5mm flat plate and it is as sweet as a nut.

I've seen similar results with experiments on my Monster and other people's bikes, always seem to work better with all flat plates and whatever logic I try, I can see no benefit to convex plates.
 

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The convex plate is a spring. Reducing the number of springs reduces the force. Not saying one way or another on using it.
 

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Discussion Starter · #8 ·
It's more the fact that it's narrower than the rest of the plates that's throwing me off - seems like it would just introduce weird/abnormal wear. Not a concern?
 

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There are a lot of combinations. I put a Barnett basket and Surflex plate kit S1816 in my bike a few thousand(5) miles ago. I took it easy for about an hours around town. It's been perfect since then and I'm picky. My recollection is the spring plate was quite a bit narrower than the stock one.
 

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Makes a difference to the way they work.

I replaced the plates in my 916 and used a convex plate to make up the thickness, at 38mm I couldn't get neutral with the engine running. I replaced the 1.5mm convex plate with a 1.5mm flat plate and it is as sweet as a nut.

I've seen similar results with experiments on my Monster and other people's bikes, always seem to work better with all flat plates and whatever logic I try, I can see no benefit to convex plates.
that's pretty much the opposite to what we used to find, but curious. do you use large diameter/easy pull slaves?

i've dealt with some 1198 dp slipper fitments where you use 4 of the conical plates to make them nice. amazed me when i was told to do it that way, but it works.
 

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that's pretty much the opposite to what we used to find, but curious. do you use large diameter/easy pull slaves?

i've dealt with some 1198 dp slipper fitments where you use 4 of the conical plates to make them nice. amazed me when i was told to do it that way, but it works.
The 1098/1198 RS bikes use about 3 to 4 convex plates
 

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that's pretty much the opposite to what we used to find, but curious. do you use large diameter/easy pull slaves?
Yes both have larger slaves so separation maybe less than standard which may compound the problem.

I find all flat plates work fine, nice engagement, no slippage or squealing but when I've tried the convex plates it always seem to cause one of the aforementioned problems - and for what benefit?
 
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