996 Clutch or Pressure Plate failures - Anyone ?
02-18-2010, 09:27 PM
#1
Rennlist Member
Thread Starter
996 Clutch or Pressure Plate failures - Anyone ?
Anyone have any clutch, really pressure plate, failures in a 996 or 986 where they end up damaging the transmission case ? I am trying to get some additional info to make sure I understand which parts are actually failing and why. Post or PM me.
Thanks in advance.
Thanks in advance.
02-19-2010, 06:31 PM
#2
Race Director
The bellhousing is the sacrifical item in the clutch/flywheel assembly. Car designers are perfectly willing to see a transmission damaged beyond repair (most transmissions do not have a replaceable/separate bellhousing, so break the bellhousing and the transmission is generally toast) as opposed to seeing the components fly out and possibly into the cabin or away from the car.
Since catastrophic failure of clutch/flywheel assembly is so rare though, this is an acceptable trade-off.
As I mentioned above, catastrophic clutch disc, pressure plate or flywheel failure is very rare. But if they fail they fail for the same reasons other assemblies/components fail.
Early failure -- infant "death" -- arises from manufacturing defects, factory assembly errors.
After a time then component mortality declines to near zero and remains there for a very long time. Maybe forever for the components while they are in service.
Generally after a long period of time old age related factors again see an increase in failure.
However, since clutches usually wear out and make themselves known to be worn out in obvious ways -- like slipping -- this usually renders the car inoperable and the clutch hardware and sometimes the flywheel are renewed. Other failures of the clutch render the car inoperable -- for instance the clutch becomes non-functional, the operation of the clutch pedal has no or not effect on the clutch's engagement. Thus the clutch never gets a chance to fail catastrophically cause it fails in a less spectacular fashion and is replaced before old age, metal fatique, can become a factor.
Once the clutch/flywheel hardware are renewed though, of course being new parts these are subject to premature failure due to defects or improper installation, same as when the car leaves the factory.
However, there are other risks: Perhaps the flywheel bolts were not replaced but the old ones reused, or the bolts were replaced with bolts of insufficient strength or even if new bolts of the right type were used they were not properly tightened.
But barring these incidents then the replacement parts generally lead non-eventful lives.
Now if the engine is modified to produce more power and if the engine is chipped which can raise the engine's red line, it is possible the stock components are not rated for the increased output and higher forces arising from the higher rpms and loads this creates. Catastrophic failure is a possibility.
Sincerely,
Macster.
02-19-2010, 11:35 PM
#3
Rennlist Member
Thread Starter
Your last paragraph is closer to our case. Just pushing the envelope a little too much I guess. In this case I think the part is fine for stock applications but it is not designed for what we are putting it thru.
I am trying to find the exact factors/conditions involved in why it fails so I can redesign accordingly or just prevent those condtions from re-occuring. The failure point is the drive straps or rivets that hold them on and they machine the case in half quick ! It's not a worn out part, nor abuse, nor manufact. defect.
I am trying to find the exact factors/conditions involved in why it fails so I can redesign accordingly or just prevent those condtions from re-occuring. The failure point is the drive straps or rivets that hold them on and they machine the case in half quick ! It's not a worn out part, nor abuse, nor manufact. defect.
I've experienced no failures of those items but that's what the bellhousing's for: To contain any of those components, or fragments of those components, should one oro more of them fail. (Racing cars have an even more substantial bellhousing, or scatter shields made of thicker/tougher metal, or special fiber blankets all of which are designed to contain the pieces should something go wrong.)
The bellhousing is the sacrifical item in the clutch/flywheel assembly. Car designers are perfectly willing to see a transmission damaged beyond repair (most transmissions do not have a replaceable/separate bellhousing, so break the bellhousing and the transmission is generally toast) as opposed to seeing the components fly out and possibly into the cabin or away from the car.
Since catastrophic failure of clutch/flywheel assembly is so rare though, this is an acceptable trade-off.
As I mentioned above, catastrophic clutch disc, pressure plate or flywheel failure is very rare. But if they fail they fail for the same reasons other assemblies/components fail.
Early failure -- infant "death" -- arises from manufacturing defects, factory assembly errors.
After a time then component mortality declines to near zero and remains there for a very long time. Maybe forever for the components while they are in service.
Generally after a long period of time old age related factors again see an increase in failure.
However, since clutches usually wear out and make themselves known to be worn out in obvious ways -- like slipping -- this usually renders the car inoperable and the clutch hardware and sometimes the flywheel are renewed. Other failures of the clutch render the car inoperable -- for instance the clutch becomes non-functional, the operation of the clutch pedal has no or not effect on the clutch's engagement. Thus the clutch never gets a chance to fail catastrophically cause it fails in a less spectacular fashion and is replaced before old age, metal fatique, can become a factor.
Once the clutch/flywheel hardware are renewed though, of course being new parts these are subject to premature failure due to defects or improper installation, same as when the car leaves the factory.
However, there are other risks: Perhaps the flywheel bolts were not replaced but the old ones reused, or the bolts were replaced with bolts of insufficient strength or even if new bolts of the right type were used they were not properly tightened.
But barring these incidents then the replacement parts generally lead non-eventful lives.
Now if the engine is modified to produce more power and if the engine is chipped which can raise the engine's red line, it is possible the stock components are not rated for the increased output and higher forces arising from the higher rpms and loads this creates. Catastrophic failure is a possibility.
Sincerely,
Macster.
The bellhousing is the sacrifical item in the clutch/flywheel assembly. Car designers are perfectly willing to see a transmission damaged beyond repair (most transmissions do not have a replaceable/separate bellhousing, so break the bellhousing and the transmission is generally toast) as opposed to seeing the components fly out and possibly into the cabin or away from the car.
Since catastrophic failure of clutch/flywheel assembly is so rare though, this is an acceptable trade-off.
As I mentioned above, catastrophic clutch disc, pressure plate or flywheel failure is very rare. But if they fail they fail for the same reasons other assemblies/components fail.
Early failure -- infant "death" -- arises from manufacturing defects, factory assembly errors.
After a time then component mortality declines to near zero and remains there for a very long time. Maybe forever for the components while they are in service.
Generally after a long period of time old age related factors again see an increase in failure.
However, since clutches usually wear out and make themselves known to be worn out in obvious ways -- like slipping -- this usually renders the car inoperable and the clutch hardware and sometimes the flywheel are renewed. Other failures of the clutch render the car inoperable -- for instance the clutch becomes non-functional, the operation of the clutch pedal has no or not effect on the clutch's engagement. Thus the clutch never gets a chance to fail catastrophically cause it fails in a less spectacular fashion and is replaced before old age, metal fatique, can become a factor.
Once the clutch/flywheel hardware are renewed though, of course being new parts these are subject to premature failure due to defects or improper installation, same as when the car leaves the factory.
However, there are other risks: Perhaps the flywheel bolts were not replaced but the old ones reused, or the bolts were replaced with bolts of insufficient strength or even if new bolts of the right type were used they were not properly tightened.
But barring these incidents then the replacement parts generally lead non-eventful lives.
Now if the engine is modified to produce more power and if the engine is chipped which can raise the engine's red line, it is possible the stock components are not rated for the increased output and higher forces arising from the higher rpms and loads this creates. Catastrophic failure is a possibility.
Sincerely,
Macster.
02-20-2010, 01:23 PM
#4
Race Director
Your last paragraph is closer to our case. Just pushing the envelope a little too much I guess. In this case I think the part is fine for stock applications but it is not designed for what we are putting it thru.
I am trying to find the exact factors/conditions involved in why it fails so I can redesign accordingly or just prevent those condtions from re-occuring. The failure point is the drive straps or rivets that hold them on and they machine the case in half quick ! It's not a worn out part, nor abuse, nor manufact. defect.
I am trying to find the exact factors/conditions involved in why it fails so I can redesign accordingly or just prevent those condtions from re-occuring. The failure point is the drive straps or rivets that hold them on and they machine the case in half quick ! It's not a worn out part, nor abuse, nor manufact. defect.
After market clutches have a beefier construction, tougher friction material (maybe more metal in it) which sometimes results in a grabbier engagement, and there can even be more friction area. This can require a different flywheel too one tolerant of the higher metal content or different friction material in the aftermarket clutch compared to the stock clutch.
Pressure plate exerts more force to avoid the engine's torque breaking the clutch loose when the generally grippier tires are fitted to take advantage of the engine's extra power output. This can make the clutch's action much stiffer. I've sat in cars equipped with aftermarket higher performance clutches and if one isn't prepared pressing down on the clutch pedal will find you being lifted out of the seat (if no seat belt on).
The force required to depress the clutch pedal is amazing and in the most extreme cases forget about driving the thing in traffic. After just a few uses one's left leg would be twitching uncontrollably from the over exertion.
All materials are designed for higher operating temperatures and higher rotational speeds. Even so the clutch may deliver a shorter service life.
If you've got a car fitted with an engine that has been modified to produce more power (and torque) then you need to find an aftermarket clutch (and probably flyhweel too) rated to take that extra power/torque. You want to avoid going overboard unless the thing a track on car cause just a bit of driving in the traffic will have you exhausted.
Sincerely,
Macster.
02-22-2010, 11:44 AM
#5
Rennlist Member
Thread Starter
I understand what you are saying Mac but we are really talking about two different issues. This is on a track only car. Rather than repeating everything see the cross post on racing forum. https://rennlist.com/forums/showthre...ferrerid=61881
Well, you'd be reinventing the wheel or in this case the clutch. Others have already done this and offer aftermarket clutch kits that are designed to accept more torque and higher rotational speeds safely.
After market clutches have a beefier construction, tougher friction material (maybe more metal in it) which sometimes results in a grabbier engagement, and there can even be more friction area. This can require a different flywheel too one tolerant of the higher metal content or different friction material in the aftermarket clutch compared to the stock clutch.
Pressure plate exerts more force to avoid the engine's torque breaking the clutch loose when the generally grippier tires are fitted to take advantage of the engine's extra power output. This can make the clutch's action much stiffer. I've sat in cars equipped with aftermarket higher performance clutches and if one isn't prepared pressing down on the clutch pedal will find you being lifted out of the seat (if no seat belt on).
The force required to depress the clutch pedal is amazing and in the most extreme cases forget about driving the thing in traffic. After just a few uses one's left leg would be twitching uncontrollably from the over exertion.
All materials are designed for higher operating temperatures and higher rotational speeds. Even so the clutch may deliver a shorter service life.
If you've got a car fitted with an engine that has been modified to produce more power (and torque) then you need to find an aftermarket clutch (and probably flyhweel too) rated to take that extra power/torque. You want to avoid going overboard unless the thing a track on car cause just a bit of driving in the traffic will have you exhausted.
Sincerely,
Macster.
After market clutches have a beefier construction, tougher friction material (maybe more metal in it) which sometimes results in a grabbier engagement, and there can even be more friction area. This can require a different flywheel too one tolerant of the higher metal content or different friction material in the aftermarket clutch compared to the stock clutch.
Pressure plate exerts more force to avoid the engine's torque breaking the clutch loose when the generally grippier tires are fitted to take advantage of the engine's extra power output. This can make the clutch's action much stiffer. I've sat in cars equipped with aftermarket higher performance clutches and if one isn't prepared pressing down on the clutch pedal will find you being lifted out of the seat (if no seat belt on).
The force required to depress the clutch pedal is amazing and in the most extreme cases forget about driving the thing in traffic. After just a few uses one's left leg would be twitching uncontrollably from the over exertion.
All materials are designed for higher operating temperatures and higher rotational speeds. Even so the clutch may deliver a shorter service life.
If you've got a car fitted with an engine that has been modified to produce more power (and torque) then you need to find an aftermarket clutch (and probably flyhweel too) rated to take that extra power/torque. You want to avoid going overboard unless the thing a track on car cause just a bit of driving in the traffic will have you exhausted.
Sincerely,
Macster.
02-22-2010, 12:32 PM
#6
Race Director
I understand what you are saying Mac but we are really talking about two different issues. This is on a track only car. Rather than repeating everything see the cross post on racing forum. https://rennlist.com/forums/showthre...ferrerid=61881
I gather you're looking at a failure of an aftermarket clutch/flywheel setup a setup I assume intended for use in the environment in which it was used?
I read the thread. Not much I can add other than the obvious: If that setup fails and one's pretty sure that the installation is right that the engine's not overreving then one or more components are defective or not up to the needs of the application. I can't see how a racing clutch/flywheel setup can call itself that and not withstand the rigors of racing. This assumes the setup not being used past its replace by date, that one is not trying to run a clutch over too many races, practice sessions and the failure you experienced is "old age" failure of the setup. Also, hard to believe a driver could do something in the car to cause the clutch to fail, unless the driver was a real bozo and I think if he was that would be obvious from other aspects of the car's performance and condition during and after a race.
Time to switch to another brand of clutch/flywheel. Unless you make the setup I can't see much value in trying to determine the failure mode, unless that is the only setup and the best there is and you need to find a way to make it work and last for you.
Sincerely,
Macster.
