Clutch intermediate plate fix ( update/revisited after a year of racing)
08-09-2011, 11:52 PM
#1
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Clutch intermediate plate fix ( update/revisited after a year of racing)
one of the most expensive parts on the 929, the intermediate plate, which has the little H tabs that are set up from the factory with a friction "rivet", and that eventually gets lose and often replaced, doesnt need to be replaced anymore.
After a year of racing, the modificatio that required just 3 roll pins, is holding just fine. no more adjusting after every race day (literally). the street use was no issue, but during races with sustained RPM for 30min between 4500 and 6500rpm, was too much for the little friction surfaces. the entire 10lb mass, only supported by 3 little flat springs when the clutch was pressed in, would allow the 6500rpm mass to vibrate only slightly enough to force the adjustment rear ward, thus causing a dragging clutch when depressed, or more often worse, and ineffective clutch, where you could only shift gears when driving, not at a stop.
anyway, its holding a year later and still is a dream to drive on the street.
How it was done was to adjust the clutch intermediate plate, and then drill a 3/16" hole into the adjusters to "pin" them in place with a 3/16" roll pin tapped into place. some have actually disasembled the IP , and driled out the stock main friction pin and installed a nut and bolt! THIS is how the IP should have been designed.
After a year of racing, the modificatio that required just 3 roll pins, is holding just fine. no more adjusting after every race day (literally). the street use was no issue, but during races with sustained RPM for 30min between 4500 and 6500rpm, was too much for the little friction surfaces. the entire 10lb mass, only supported by 3 little flat springs when the clutch was pressed in, would allow the 6500rpm mass to vibrate only slightly enough to force the adjustment rear ward, thus causing a dragging clutch when depressed, or more often worse, and ineffective clutch, where you could only shift gears when driving, not at a stop.
anyway, its holding a year later and still is a dream to drive on the street.
How it was done was to adjust the clutch intermediate plate, and then drill a 3/16" hole into the adjusters to "pin" them in place with a 3/16" roll pin tapped into place. some have actually disasembled the IP , and driled out the stock main friction pin and installed a nut and bolt! THIS is how the IP should have been designed.
08-10-2011, 01:34 PM
#3
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Here you go. the beauty of this mod is it is done ON the car, no removing the clutch. just need a long 1/8 drill bit and a few roll pins and a tap to push them in. DONE, never to be touched again!
the problem with the bolt , is that you cant really tighten it on the car. no room for a socket in there.
plus, even with the proper amount of friction on the bench before installation, the vibration, and forces when the floating disc is spinning 6500rpm, resting on the H tabs , could be too much for that design as welll in race applicaions. so, the pinning is perfect because it is LOCKED into position, never to move.
the problem with the bolt , is that you cant really tighten it on the car. no room for a socket in there.
plus, even with the proper amount of friction on the bench before installation, the vibration, and forces when the floating disc is spinning 6500rpm, resting on the H tabs , could be too much for that design as welll in race applicaions. so, the pinning is perfect because it is LOCKED into position, never to move.
08-10-2011, 05:17 PM
#5
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The stock design the intermediate plate which floats between two friction discs is self adjusting. So when the disc closest to the flywheel wears and gets thinner those riveted anchor locations can move since the hole where the rivets mount is slotted. Kibort is adjusting the plate and locking the anchors by drilling and pinning them.
It does seem to be working for him and new intermediate plates are expensive....to state that this is how they should have been made is one man's opinion.
It does seem to be working for him and new intermediate plates are expensive....to state that this is how they should have been made is one man's opinion.
08-10-2011, 07:29 PM
#6
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one man's opinion that has had good and bad intermediate plates and has not ever had to buy one. this one is off my original '84 car!
the reason that it is a good idea, is that if you are racing, the settings (which solely rely on the friction of the stock set up H pad and rivet), can move based on the floating part of the disc (about 10lb and 1ft in diameter) spinning at 6500rpm and having rapid changes of direction, mostly deceling, which gives the floating part even MORE leverage aganst the pads. anyway, with proper adjustment, the 1mm setting alows for release of the discs on the flywheel. the good news , is that there is also about 1mm space on the back side too, so that if the discs wear, it is self adjusting for the contact pressure.
the only downside, is if you really wear out you clutch discs, which i have never seen in 15 years of racing and 25 years of 928 ownership, with 100s of thousands of miles logged.
the reason that it is a good idea, is that if you are racing, the settings (which solely rely on the friction of the stock set up H pad and rivet), can move based on the floating part of the disc (about 10lb and 1ft in diameter) spinning at 6500rpm and having rapid changes of direction, mostly deceling, which gives the floating part even MORE leverage aganst the pads. anyway, with proper adjustment, the 1mm setting alows for release of the discs on the flywheel. the good news , is that there is also about 1mm space on the back side too, so that if the discs wear, it is self adjusting for the contact pressure.
the only downside, is if you really wear out you clutch discs, which i have never seen in 15 years of racing and 25 years of 928 ownership, with 100s of thousands of miles logged.
The stock design the intermediate plate which floats between two friction discs is self adjusting. So when the disc closest to the flywheel wears and gets thinner those riveted anchor locations can move since the hole where the rivets mount is slotted. Kibort is adjusting the plate and locking the anchors by drilling and pinning them.
It does seem to be working for him and new intermediate plates are expensive....to state that this is how they should have been made is one man's opinion.
It does seem to be working for him and new intermediate plates are expensive....to state that this is how they should have been made is one man's opinion.
08-10-2011, 07:41 PM
#7
Nordschleife Master
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08-10-2011, 09:11 PM
#8
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variance in the intermediate plate, or clutch disc wear. ive done many where i can do both extremes and make the car unable to get the car in gear. wide open does it, all the way closed does it too. call me one man, but there is a REASON the factory spent so much time on the design and the instructions.
check your clutch discs and they are probalby a .5mm worn on each.
you saw mine, they still had the part numbers inked on the surface!
at full thickness, they will drag on the pressure plate friction surface if you crank them all the way open. if they dont, you have a special case. truely one mans experience. (or maybe two )
mk
check your clutch discs and they are probalby a .5mm worn on each.
you saw mine, they still had the part numbers inked on the surface!
at full thickness, they will drag on the pressure plate friction surface if you crank them all the way open. if they dont, you have a special case. truely one mans experience. (or maybe two
) mk
08-10-2011, 11:57 PM
#9
Nordschleife Master
08-11-2011, 02:15 AM
#10
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must be variances in differnet pressure plates, or disc thicknesses.
what you are saying is that you push the adjusters all the way rearward and when you push in the clutch, the pressure plate is pullled so far far back that the discs cant put any pressure on the pressure plate rearward. maybe this is a function of the clutch lever, slave push range, and some other things.
I just havent seen it in a few 928s ive adjusted.
Mk
what you are saying is that you push the adjusters all the way rearward and when you push in the clutch, the pressure plate is pullled so far far back that the discs cant put any pressure on the pressure plate rearward. maybe this is a function of the clutch lever, slave push range, and some other things.
I just havent seen it in a few 928s ive adjusted.
Mk
08-11-2011, 03:05 PM
#13
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I dont understand . if they are loose, the Hs will move rearward based on the spring pressure (flat spring) forcing the friction surface disc rear ward. it stops via the H stops. if that distance it moves rearward alows it to keep contact with the pressure plate surface, it will drag on the drive shaft and you wont be able to get it into gear because the friction of the synchros is not sufficient to slow the shaft down to a stop. if the pressure plate being levered rear ward by the clutch lever is greater, then that distance might not allow drag on the pressure plate. the H's being loose will alow for movement rearward, there are NO forces that could move them frontward, unless the clutch pack making contact when the clutch pedal is released , needs a greater distance to make contact with the flywheel, and then the IP could press on the front of the H's, and move them forward. (rare).
08-15-2011, 10:19 AM
#14
Arent you afraid the pins will drift themselves out by centrifugal force? At that speed, they could lead to some damage, I expect. I'd much rather have some allen bolts inserted with some Loctite on the thread. As a reference, your wheel valve caps aren't only there to prevent dirt entering the valve, but also, at high velocities, the valve may open itself due to centrifugal force!
08-15-2011, 12:08 PM
#15
Captain Obvious
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Arent you afraid the pins will drift themselves out by centrifugal force? At that speed, they could lead to some damage, I expect. I'd much rather have some allen bolts inserted with some Loctite on the thread. As a reference, your wheel valve caps aren't only there to prevent dirt entering the valve, but also, at high velocities, the valve may open itself due to centrifugal force!