Centerlock Hub Failure Buttonwillow 5/25/12
05-31-2012, 12:52 AM
#31
), see above. The paint softens and squeezes out under high heat (tracking), a void is created thereby causing the CL nut torque to fall off and then stress the hub. As I understand it, only some of a particular sellers wheels were affected.
05-31-2012, 12:53 AM
#32
Rennlist Member
Glad u and passenger are ok. Hopefully PCNA will come thru for u. Coolant fittings and now CL's are potential for major disasters both street or track. Mike
05-31-2012, 01:07 AM
#34
Rennlist Member
Not correct my friend (he actually is a friend, not being condescending ), see above. The paint softens and squeezes out under high heat (tracking), a void is created thereby causing the CL nut torque to fall off and then stress the hub.
As I understand it, only some of a particular sellers wheels were affected.
), see above. The paint softens and squeezes out under high heat (tracking), a void is created thereby causing the CL nut torque to fall off and then stress the hub. As I understand it, only some of a particular sellers wheels were affected.
Ha my friend Savyboy! Ya caught me editing after I read your post......busted!
I fixed my post above yours!!!!
Everyone is trying to figure out the mystery....we may never know the real answer. But hopefully we do find out for everyone's future safety.
Cheers!
Doug N.
05-31-2012, 01:10 AM
#35
Instructor
Thread Starter
No paint on the mating surfaces, and the splined lock nut was verified in place prior to going out (I am a stickler for this). To me this says unless there was deformation in the system, proper torque should have been maintained.
05-31-2012, 01:10 AM
#36
Let me add that visual inspection of the parts will tell a tale and a history. If the drive pins are damaged, then CL nut torque was lost. Drive pins should never have any markings except possible light scratches caused by mounting/dismounting the wheel.
As well there will be visible evidence on the conical contact areas of both the CL nut and wheel if the nut was previously not to torque. The hub and wheel will also show wear (galling/metal transfer) on the inboard contact areas if the wheel was ever loose for a period of time as would be the case unless it was an instantaneous failure. There is no need for guessing or anecdotal evidence, the parts will tell the story.
I am wholly sympathetic to Geoff's situation but I am not prepared to run pitchfork first toward Porsche unless I know more facts and let the parts talk to me. I'd like to see a photo of both the hub part as attached to car and of the conical surface of the centerlock nut. Both cleaned.
As well there will be visible evidence on the conical contact areas of both the CL nut and wheel if the nut was previously not to torque. The hub and wheel will also show wear (galling/metal transfer) on the inboard contact areas if the wheel was ever loose for a period of time as would be the case unless it was an instantaneous failure. There is no need for guessing or anecdotal evidence, the parts will tell the story.
I am wholly sympathetic to Geoff's situation but I am not prepared to run pitchfork first toward Porsche unless I know more facts and let the parts talk to me. I'd like to see a photo of both the hub part as attached to car and of the conical surface of the centerlock nut. Both cleaned.
Last edited by savyboy; 05-31-2012 at 01:27 AM.
05-31-2012, 01:24 AM
#38
The hub fails at the threaded (outboard) area due to metal fatigue because side loads were fed into the threads instead of via wheel flange to hub flange where they are supposed to be transmitted. If you know and can picture the CL pieces working together this will make sense.
Another way to think of it: If the CL nut ever is loose it allows the wheel cornering loads to act as a pry bar, if you will, against the threads. Instead of the loads going from flange to flange with the threads simply acting to hold the torque of the nut and not the cornering loads.
Another way to think of it: If the CL nut ever is loose it allows the wheel cornering loads to act as a pry bar, if you will, against the threads. Instead of the loads going from flange to flange with the threads simply acting to hold the torque of the nut and not the cornering loads.
05-31-2012, 01:36 AM
#39
Nordschleife Master
The hub fails at the threaded (outboard) area due to metal fatigue because side loads were fed into the threads instead of via wheel flange to hub flange where they are supposed to be transmitted. If you know and can picture the CL pieces working together this will make sense.
Another way to think of it: If the CL nut ever is loose it allows the wheel cornering loads to act as a pry bar, if you will, against the threads. Instead of the loads going from flange to flange with the threads simply acting to hold the torque of the nut and not the cornering loads.
Another way to think of it: If the CL nut ever is loose it allows the wheel cornering loads to act as a pry bar, if you will, against the threads. Instead of the loads going from flange to flange with the threads simply acting to hold the torque of the nut and not the cornering loads.
05-31-2012, 03:40 AM
#40
Addict
Rennlist Member
Rennlist Member
Hey Geoff
I felt really bad when I learn your off and RR CL failure. Your GT3 spend a night at my garage last year while Lar and I got our car ready for track event. I hope you will be able to resolve this issue in a satisfactory manner that results in you back on the track in a properly repaired (or new) GT3.
Back to your description of the wheel hub damage "Inspection shows the centerlock hub completely failed/sheared at the the base of centerlock nut. Centerlock nut was recovered intact and shows little to no damage. Threaded piece of hub is still contained within nut". This concerns me greatly that the CL hub failed at the base. I was never a fan of the 997.2 CL. Seeing how people labor over their CL on the track sometimes up to 20 minutes or more just for tire change is just not right. Racing technology is suppose to improve the strength and efficiency of mechanical parts and not not the other way around. I always had my concern about the hollow CL hub design ... it just does not look right and sturdy enough to hold the stress of the wheel under track condition.
My Cup car and also formula one race car have solid center lock stud instead of hub. It will take a Hercule effort to bend or destroy these studs. It also contain a safety pin at the end which help prevent the wheel from flying off in case of a loosen center nut. I don't trust any technology other than a solid center stud or just plain old five wheel studs.
Best wish in your endeavor to resolve this mechanical failure accident.
Mike
Foumula one CL
Street 997.2 GT3 CL componenets
vs GT3 Cup CL
I felt really bad when I learn your off and RR CL failure. Your GT3 spend a night at my garage last year while Lar and I got our car ready for track event. I hope you will be able to resolve this issue in a satisfactory manner that results in you back on the track in a properly repaired (or new) GT3.
Back to your description of the wheel hub damage "Inspection shows the centerlock hub completely failed/sheared at the the base of centerlock nut. Centerlock nut was recovered intact and shows little to no damage. Threaded piece of hub is still contained within nut". This concerns me greatly that the CL hub failed at the base. I was never a fan of the 997.2 CL. Seeing how people labor over their CL on the track sometimes up to 20 minutes or more just for tire change is just not right. Racing technology is suppose to improve the strength and efficiency of mechanical parts and not not the other way around. I always had my concern about the hollow CL hub design ... it just does not look right and sturdy enough to hold the stress of the wheel under track condition.
My Cup car and also formula one race car have solid center lock stud instead of hub. It will take a Hercule effort to bend or destroy these studs. It also contain a safety pin at the end which help prevent the wheel from flying off in case of a loosen center nut. I don't trust any technology other than a solid center stud or just plain old five wheel studs.
Best wish in your endeavor to resolve this mechanical failure accident.
Mike
Foumula one CL
Street 997.2 GT3 CL componenets
vs GT3 Cup CL
05-31-2012, 04:23 AM
#41
Geoff,
I am very sorry to read this and find it quite concerning. It might be a bit of a reach, but given the circumstances I would consider taking the time to send the torque wrench used to an NIST lab to have it recertified. It shouldn't cost much but will more importantly take one more variable out of the equation as to whether or not it was really torquing to the correct spec.
I sincerely hope this all works out in your favor.
I am very sorry to read this and find it quite concerning. It might be a bit of a reach, but given the circumstances I would consider taking the time to send the torque wrench used to an NIST lab to have it recertified. It shouldn't cost much but will more importantly take one more variable out of the equation as to whether or not it was really torquing to the correct spec.
I sincerely hope this all works out in your favor.
05-31-2012, 06:53 AM
#43
The most important thing is that you're unhurt.
It has been a long time now that Porsche's policy has been to void the warranty on tracked cars. Couple that with the aftermarket wheels on the car at the time of the incident, and it's gonna be an uphill battle to get ANYTHING out of PCNA. If you really feel they are in the wrong and owe you a car, I would prepare for the worst by contacting admin, having this thread deleted and getting in touch with an attorney.
They know we're here and read these forums. It is unlikely that anybody from Porsche is going to open up to the posters here, that would be career suicide.
It has been a long time now that Porsche's policy has been to void the warranty on tracked cars. Couple that with the aftermarket wheels on the car at the time of the incident, and it's gonna be an uphill battle to get ANYTHING out of PCNA. If you really feel they are in the wrong and owe you a car, I would prepare for the worst by contacting admin, having this thread deleted and getting in touch with an attorney.
They know we're here and read these forums. It is unlikely that anybody from Porsche is going to open up to the posters here, that would be career suicide.
05-31-2012, 07:39 AM
#44
Addict
Rennlist Member
Rennlist Member
If anything, these forums actually work in favor of the victim and not in favor of PCNA. There are multiple engineers in these forums, and the design defects have been described.
The fact that most car shops nationwide don't have the tools to install wheels on these cars makes it a liability right away. How can tire shops replace or repair tires on these cars with Center Lock wheels, when the tools to be used have to be of certain type, and the torque specs keep changing per the manufacturer.
If the failure would have been a CL corner to be replaced, it might have been done under warranty, but a totalled car due to the same failure would hardly be replaced under warranty due to the replacement costs.
If Porsche is officially voiding warranties on tracked cars (not even raced), they are entering the Nissan, Subaru, Mitsubishi territory. It is safe for Porsche, but not safe enough.
What Porsche has not acknowledged is that a void warranty is not the same as a release of liability. If death or heavy injuries are sustained due to a design failure in a car, it is not a warranty issue anymore, it becomes a liability on the car manufacturer. This is why sometimes car manufacturers issue recalls on cars already out of warranty, because their beans counters have found the liability costs are vastly higher than the cost of the recall.
If I were the decision maker at PCNA on this topic, I would issue a release of liability with every car sold, and every car already sold, a nationwide notification that the car are not intended to be used at racetracks, (track days, DE, Club Racing, any form of racing), and any failures occurred at those venues during unauthorized usage would be a liability of the car owner and/or driver. This would be much cheaper, than issue a recall to replace CL with 5-lugs, which requires new wheels and hub parts in the cost of $12k for parts and labor, for all the 997.2 Turbo, Turbo S, Carrera GTS, 997.2 GT3, 997.2 GT3 RS, RS 4.0, GT2 RS in U.S. soil. This saves PCNA near $30MM, and it saves them even more considering other known failures happening at racetracks (like the defective clutch in the 3.8RS, and the dangerous coolant fittings failing on all Mezger engines, the failing diff and handling issues it creates, and the near killing ice mode).
I would lawyer up if this happened to me. PCNA would have to prove that an aftermarket wheel had caused the problem, and that's a challenge for them, as the parts are already showing what failed.
The fact that most car shops nationwide don't have the tools to install wheels on these cars makes it a liability right away. How can tire shops replace or repair tires on these cars with Center Lock wheels, when the tools to be used have to be of certain type, and the torque specs keep changing per the manufacturer.
If the failure would have been a CL corner to be replaced, it might have been done under warranty, but a totalled car due to the same failure would hardly be replaced under warranty due to the replacement costs.
If Porsche is officially voiding warranties on tracked cars (not even raced), they are entering the Nissan, Subaru, Mitsubishi territory. It is safe for Porsche, but not safe enough.
What Porsche has not acknowledged is that a void warranty is not the same as a release of liability. If death or heavy injuries are sustained due to a design failure in a car, it is not a warranty issue anymore, it becomes a liability on the car manufacturer. This is why sometimes car manufacturers issue recalls on cars already out of warranty, because their beans counters have found the liability costs are vastly higher than the cost of the recall.
If I were the decision maker at PCNA on this topic, I would issue a release of liability with every car sold, and every car already sold, a nationwide notification that the car are not intended to be used at racetracks, (track days, DE, Club Racing, any form of racing), and any failures occurred at those venues during unauthorized usage would be a liability of the car owner and/or driver. This would be much cheaper, than issue a recall to replace CL with 5-lugs, which requires new wheels and hub parts in the cost of $12k for parts and labor, for all the 997.2 Turbo, Turbo S, Carrera GTS, 997.2 GT3, 997.2 GT3 RS, RS 4.0, GT2 RS in U.S. soil. This saves PCNA near $30MM, and it saves them even more considering other known failures happening at racetracks (like the defective clutch in the 3.8RS, and the dangerous coolant fittings failing on all Mezger engines, the failing diff and handling issues it creates, and the near killing ice mode).
I would lawyer up if this happened to me. PCNA would have to prove that an aftermarket wheel had caused the problem, and that's a challenge for them, as the parts are already showing what failed.
