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After some slipper clutch research

8K views 15 replies 9 participants last post by  desmo_speeding 
#1 ·
here is one excerpt I read, then I asked a few GP racers in the area.

"STM Slipper Clutch for Ducati, Honda, Aprilia, Suzuki and Yamaha. Innovative STM engineering for a variety of bike applications. Slipper clutch technology reduces rear wheel slip during hard engine braking and acceleration. Used by most factory race teams and super-enthusiast weekend and track day riders. Light weight billet construction lasts longer than OEM clutch material, while providing lighter and more positive clutch feel."

These things are really nothing more than a clutch with an adjustable pressure plate setting. They DO slip in both directions. The mechanism is sometimes a torque sensing switch, that toggles between two settings.

I am not sure this is for me, just because when set-up right, they must eat the plates much faster than normal. If clutch plates are no big deal, and the maintenance, It would probably be a great thing. It might ruin my "wheelie show-off hour" I do on the weekends for the kids, so I might have to pass. I do hate when I grab too many gears, my wheels hops, and the husky will die.

I hasn't done that in a while, maybe that was a break-in issue only.
 
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#2 ·
I think the idea is that they are adjustable regarding different applications. For a GP race you would make it slip under decel much, much more than what you would for a SM setup. Initiating a turn and downshifting two gears at 120mph without a slipper is bloody dangerous! Hell, just backing off the throttle mid turn is risky on my RS250. But this is what the AMA guys were doing last year and loving it thanks to the slipper clutches.

The advantage for SM from talking with folks that race and run slippers is that you don't worry about stalling the bike or traumatizing your tranny (shifting into 1st gear at 50mph is not that healthy for any tranny with a standard clutch). You just drop it into 1st and let go of the clutch and...instant controlled slide allowing you to back it in without feathering the clutch (as if I'm even close to mastering that!).

So the adjustability is the key. Folks running the new KTM slipper clutch swear by them. I've never heard of anyone who tried a slipper and didn't like it. Once the LC4 version is available I'm saving my pennies... :thumbup:

SuperRetard said:
here is one excerpt I read, then I asked a few GP racers in the area.

"STM Slipper Clutch for Ducati, Honda, Aprilia, Suzuki and Yamaha. Innovative STM engineering for a variety of bike applications. Slipper clutch technology reduces rear wheel slip during hard engine braking and acceleration. Used by most factory race teams and super-enthusiast weekend and track day riders. Light weight billet construction lasts longer than OEM clutch material, while providing lighter and more positive clutch feel."

These things are really nothing more than a clutch with an adjustable pressure plate setting. They DO slip in both directions. The mechanism is sometimes a torque sensing switch, that toggles between two settings.

I am not sure this is for me, just because when set-up right, they must eat the plates much faster than normal. If clutch plates are no big deal, and the maintenance, It would probably be a great thing. It might ruin my "wheelie show-off hour" I do on the weekends for the kids, so I might have to pass. I do hate when I grab too many gears, my wheels hops, and the husky will die.

I hasn't done that in a while, maybe that was a break-in issue only.
 
#3 ·
SuperRetard said:
here is one excerpt I read, then I asked a few GP racers in the area.

"STM Slipper Clutch for Ducati, Honda, Aprilia, Suzuki and Yamaha. Innovative STM engineering for a variety of bike applications. Slipper clutch technology reduces rear wheel slip during hard engine braking and acceleration. Used by most factory race teams and super-enthusiast weekend and track day riders. Light weight billet construction lasts longer than OEM clutch material, while providing lighter and more positive clutch feel."

These things are really nothing more than a clutch with an adjustable pressure plate setting. They DO slip in both directions. The mechanism is sometimes a torque sensing switch, that toggles between two settings.

I am not sure this is for me, just because when set-up right, they must eat the plates much faster than normal. If clutch plates are no big deal, and the maintenance, It would probably be a great thing. It might ruin my "wheelie show-off hour" I do on the weekends for the kids, so I might have to pass. I do hate when I grab too many gears, my wheels hops, and the husky will die.

I hasn't done that in a while, maybe that was a break-in issue only.
I have slipper clutches on both my 996 and my 999.

NO, they do not slip both ways, they slip one-way per their design. IF they slipped both ways....you wouldnt go very far now would you :hammer: :D
slipper clutches use a few different configurations, ramps and so forth. They slip ONE way mechanically, if they slip the other way, its because the clutch plates themselves are fragged, and slip in the same manner as any other standard clutch would slipp if it were worn out.
 
#4 ·
desmo_speeding said:
I have slipper clutches on both my 996 and my 999.

NO, they do not slip both ways, they slip one-way per their design. IF they slipped both ways....you wouldnt go very far now would you :hammer: :D
slipper clutches use a few different configurations, ramps and so forth. They slip ONE way mechanically, if they slip the other way, its because the clutch plates themselves are fragged, and slip in the same manner as any other standard clutch would slipp if it were worn out.
Let's get one thing straight, what I know about these you could engrave on the head of a pin in old english script, 48pt fonts.

BUT, that excerpt is from someone who manufactures these things, and BRAKING AND ACCELERATION means that they slip both directions, TO ME anyway, how do explain that? :infrandom
 
#6 ·
SuperRetard said:
Let's get one thing straight, what I know about these you could engrave on the head of a pin in old english script, 48pt fonts.

BUT, that excerpt is from someone who manufactures these things, and BRAKING AND ACCELERATION means that they slip both directions, TO ME anyway, how do explain that? :infrandom
You're misunderstanding something you've read or the information wasn't presented to you properly. However you came to be misinformed, I'll try to clear it up for you: slipper clutches hold under acceleration and slip under deceleration. The amount a given slipper clutch slips under deceleration can vary and there is normally some provision for adjusting the amount of slip.

In addition, you can pull in the clutch using the clutch lever and release the clutch entirely just as you can with a conventional clutch.

Now you know. :)
 
#7 ·
There is an excellent article on slipper clutches in the May 05 issue of Roadracing World.

Eric Landstrom said:
You're misunderstanding something you've read or the information wasn't presented to you properly. However you came to be misinformed, I'll try to clear it up for you: slipper clutches hold under acceleration and slip under deceleration. The amount a given slipper clutch slips under deceleration can vary and there is normally some provision for adjusting the amount of slip.

In addition, you can pull in the clutch using the clutch lever and release the clutch entirely just as you can with a conventional clutch.

Now you know. :)
 
#8 ·
confusion

You are confusing a Slipper Clutch with a TC (Traction Control ) clutch also refered to as a slipper clutch that is used in Moto GT etc. :hmmm:

check these out it should clear it up for you :thumbup:

taken from http://www.hpiracing.com/graphics/instr/a507.pdf
Slipper Clutch Adjustment.
The Traction Control Clutch provides smooth acceleration on slippery surfaces and protection for the belts and gears. Adjust the Traction Control Clutch so that the clutch slips enough to protect the gears and belts from damage when landing from jumps.
NOT WHAT WE WANT ! :headshake :hammer:

This is a Slipper Clutch as we know it ! :bowdown: :bowdown:
full article at http://www.sigmaperformance.com/slipperclutch.html

So how does a slipper clutch work? :headscrat

When the engine power is driving the bike forwards in the normal direction the little ramps lock solid; the clutch acts completely normally. (see pics at bottom)

Under a slowing situation when the engine is being turned over by the rear wheel the clutch is forced to take the load in the opposite direction, this forces the centre of the clutch up the 45-degree ramps; so starting to force the clutch pack apart.

As soon as the clutch pack stops gripping (i.e. when the centre has risen slightly on its ramps) most of the force to hold the pack apart is lost and theoretically clutch grip is re-established as the pack tries to come back together. In practice the clutch establishes an equilibrium position where there is just enough force being transmitted to hold the clutch apart (i.e. to hold the centre partially up the ramps) yet just enough to stop the engine being revved up, this equilibrium point can be adjusted either by varying the spring rate or the effective preload on the springs holding the clutch together or by varying the height of the assembled clutch pack. This is why you will often see theoretically rich well-funded race teams sorting through endless piles of seemingly knackered clutch plates trying to get precise pack thicknesses they want to give their rider the feel he is used to.

More sites: http://www.hardracing.com/STM.htm

Hope this clears it up for you :D :thumbup:
 
#9 ·
SuperRetard said:
.....hard engine braking and acceleration.
Yeah, I can totally see why that statement is confusing the hell out of people but if I may break out some high school physics, acceleration is a rate of change of velocity (basically speed). A non-constant speed is an acceleration, and since velocity is a vector quantity (containing both magnitude and direction) so is acceleration.

My whole point is that sometimes techie people write these things and since acceleration in the negative direction is deceleration, their statement is technically correct however messed up. And while I have never done any reading up on slipper clutches, I have always gathered that they slip only one way and that is under braking. :)
 
#10 ·
I am still wondering if they are worth $800 just for the part, and just how adjustable they really are. I know this, the 2004 Husqvarna SM450R would benfit from one if it works even half as well as claimed.

I can understand how one with a 85degree-5degree-90degree triangle on the face, would ramp-slip one way, and lock-up in the other direction, but I can't get is how that design would ever slip like a regular clutch does.

If it is symetrical, I can see it slipping in both directions, but engine braking is so much more intense than acceleration, its not even funny, you can go from 600rpm to 14k in the blink of an eye on some machines, so It would only slip a little, unless you were dumping the clutch from redline, on acceleration, with a set-up that would slip rather (I did some physics on this, but will go into it with anyone who wants on a private message) easily on normal deceleration. I would not have assumed the huge mismatch in force coefficients on these.


UPDATE: 8:30pm; I rode a Suzuki GSXR-1000 today with a slipper clutch and it was very, very cool. It works just how you would want it to , without anything different except how you use compression braking. I will surely get one now for the $800, I would say they are worth every penny.

We also tested push starting, and you can push start the bike, but only in 4th gear or above, and pushing pretty fast, other than that, the clutch will slip, when it slips like that, (when push starting) you can hear the clutch popping into slip-position, it actually pops into position, all at once, not a general slipping motion, if the force is coming from the rear wheel, in a significant way, it goes into that position. The trick to push starting, is to push it in a high gear and pop the clutch while still going slow. Sort of the opposite of how you normally push-start a bike.
 
#11 ·
SuperRetard said:
Anyway, I challenge someone to find a diagram of one or an article that explains how they work in detail. I am sure there are more than one design.
Did you read the Sigma Performance article that PaMotard linked to above? It's an excellent explanation with photos and such. A great read, if you haven't yet.

I did a "tech talk" workshop for my local Ducati group, and slipper clutches were one of the topics. Like DesmoSpeeding above, I have slippers in a couple of my bikes. The Sigma explanation is great, but if you prefer you can click here to see a graphic I created for that discussion. Basically, in an STM/Sigma/Bucci type slipper, the hub pushes the pressure plate in the clutch-release direction under reverse torque loads. Under forward-torque loads (power on), the hub goes back down the balls/ramps and the pressure plate applies load to the clutch plates normally.

The Surflex is a slightly different design, in that it relieves pressure plate load by pushing the spring posts (and hence the spring cups/caps) away from the clutch pack. They are physically different designs, with the same goal in mind. Both are tuned using varying thicknesses of steel plate to change the point at which the load is decreased enough to slip under engine braking conditions.

My 748 has a slipper set VERY loose, and in combination with some high-compression pistons, it slips with very little provocation in closed-throttle operation. My streetbike has a Surflex slipper, and while it also performs nicely, the slip action is set much higher, so that it eliminates chatter but will provide some engine braking up to a point.

I hope the diagram is of some help, and be sure to read the links as provided in PaMotard's post. There are excellent explanations from folks who know a lot more about it than I do.
 
#13 ·
I can't speak for Supermoto, as I'm still a newb, but if it's anything like a "regular" sportbike - proper suspension setup (springs, valving, geometry) should probably be one of the first things on the list.

When I got my 450, first move was to pull the forks and shock to have them setup for my weight and riding needs.
 
#14 ·
Nice "SBK". Thank you for putting forth the typing effort.......... I was just too lazy.

DEFINITELY suspension before slipper. Suspension works for you every millisecond of your ride/race/whatever. A slipper clutch is an enhancement over a standard clutch, and basically only becomes an advantage on deceleration/cornering. And, once you have both........you will be even smoother and faster.

But, no question about it: suspension first. for that matter I firmly believe it should be suspension before anything else. I have seen more examples of this being the very BEST path to lower lap times, fewer crashes, improved learning curve for rider; that I think it should be tatoo'd on every new riders palm (forehead, ass,...............you decide).

you will always go quickest on a machine that is tuned to handle, not necessarily on one that is tuned for the most HP, etc.
 
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