Garth S

Actually, I think that is the toe link .... item #4 is the kinematic link: but your point is well made - if the drop link bracket is either poorly positioned ... or moves in service, the drop link will kiss the toe link.
That concern had me add a (second) locknut below the link bracket on the shock body: in conjunction with the locknut on top, this assures that any torque against the bracket will always leave it in a tightening mode.

Ritter v4.0

I feel like driving right over to my mechanic to have it checked out.
I had new HD Bils and lowered less than 10k ago and everything looked ok then but . . .

touf

I ll take beeter pics of the ball joint fracture today.
ERP doesn t make lower ARMS. There is a RS lower ARM which I believe the difference to be is better rubber bushings!

TCallas

I am short on time right now and I have not had the opportunity to read this entire thread but I would like to offer some of my experience. In 1996 when running the GT2 cars in the USA and Europe we discovered that we had to keep a close eye on the lower control arm balljoints and toe links due to wear. The balljoints on these would get play but they would usually make it through the remainder of an endurance race however the wear or damage is obvious. In this case, I feel this wear may have been missed during an inspection by your mechanic/s. While running these cars I worked closely with the engineers at Weissach and we discovered the lower control arm balljoint nut to get loose. After the balljoint nut gets loose the hub, AKA the upright and AKA the wheel bearing carrier, the balljoint hole gets oblonged and shortly afterwards you have balljoint failure from the balljoint being run loose. I am not worried about everyone having this same catastrophic failure because it has been very easy to spot a loose balljoint nut or a worn out balljoint. A good mechanic has the ability to inspect these and tell you if it is safe for you to go to the track. I would recommend that you educate yourselves (if you do not already know) on the proper inspection techniques so you can check for this issue throughout a track event weekend.

tj90

Are you talking about simply jacking up the car and checking wheel play by pushing and pulling on the bottom of the wheel???

TCallas

Basically yes but it's best to do this immediately after coming off of the track while all the links are still hot. When the car is jacked up, you grab the rear tire with gloves on at the 12 and 6 O'clock positions and move it as hard as you can to check the lower ball joint. You can also grab it at the 9 and 3 O'clock positions to check the toe link ball joint. It's actually very simple. If there is any play at all in either one of these then you usually have a faulty joint. First off though you need to keep checking the lower/A-arm ball joint nut to see if it is loose at all. How tight this should be I cannot tell you in an e-mail. I go by feel. Make sure that the ball joint nut is tight all the time and you should be OK for a long time to come. I have never seen a 993 rear lower/A-arm ball joint failure without being run loose for quite some time. Do not panic on this one. It's all about inspecting your race car every 2-3 or so run sessions to make sure that it is safe for the track.

ppressle

Thanks Tony!

Jack Esposito

The failure of the ball joint looks like a tensile failure at the thread-to-shank location, not a shear failure. An over tightened nut can cause this type of tensile failure, but that probably wasn't the case here. A loose nut is more likely to have caused the stud to fail in tensile fatigue during cyclic loading. The right amount of preload (nut torque) is required on the stud to avoid a fatigue failure. To work the stud to failure in fatigue you have to overcome the preload that the nuts puts on the stud. If nut is loose or not tighened to the specified torque then it is easy to overcome the preload and the stud will fail in tensile fatigue.

Jack

Flying Finn

Tony,

Thanks for the valuable info. Experienced information and tips are always very much appreciated.

GeoT3

according to the shop manual the ball joint nut and upper control arm ball joint nuts should be torqued to 55 lbs. and also noticed that these nuts do not have cotter pins to secure the nuts :-( I wonder why?

BTW, the lower shock nut should be torqued to 63 ft lbs.

Jack of Hearts

I have been waiting for someone else more knowledgable to post this but no one did so here goes. Feel free to correct me if I have this wrong. (esp..Tony, Steve, etc.) My understanding is that with the BILSTEIN M030 or any aftermarket set-up that uses a threaded attachment for the sway bar drop link, the normal action of the sway bar (esp lots of hard, swoopy turns, i,e,, racing) can loosen the mount resulting in it twisting. Once it twists the rear drop link no longer has required clearance and begins to strike the A-arm. (Leaving marks not unlike Toufs.) So if the suspension tries to compress and is stopped by a twisted link, excessive force will be taken up by other components until the weakest link fails. Read: Balljoint. Several previous posts showed the ball joint shearing at the end of the screw threads, a typical mechanical failure point. The simple fix, as I understand it, is simply to put an additional threaded collar UNDER the sway bar link mount (as someone on this thread mentioned). kelly posted a good pic of this a couple of weeks ago. None of this is to disagree with Tony: He knows more than I've forgotten. But I suspect the failures he saw were on cars raced flat out with race tires. So anyway, by all means check your balljoints. But also, make sure your rear bar pickup is not rotating!

chris

Jack of Hearts

wait....i meant Tony's forgotten more than I ever knew...or something...oh nevermind.

Flying Finn

Chris,

You're correct. Especially with older PSS-9s, there were problems you wrote and that can cause problems for drop ling &/or lower arms. In newer shocks, the third thread collar is included so the problem can be avoided.

When my PSS-9 was installed (without the 3rd collar), I looked at it and thought it could be a problem so collar was hammered really tight and I marked it with the black permanent marker so that I could see if it has turned. I always pay attention to those marks when I change tyres and at the same time, check suspension.

However, there has been a lot (and I'm surpriced how much) questions and wrong installations done by Porsche shops who have mounted the drop links wrongly, or used wrong drop link and monted the sway bar over the lower arm etc. causing the sway bar to hit the lower arm (shop that did my installation was going to screw it up also but I checked the installation and gave them instructions before they made the mistake and finlayzed the installation).
This kind of wrong installation can certainly cause problems.

TRINITONY

Also in viperbobs handout he does mention that after driving on the track you should check them to ensure that they don't come loose, the mount that is. I think I need to get an extra collar....

Edward

Late to this, but likewise glad that you (Touf) didn't get hurt ...as you said, with a spinning car through a gravel trap you could have fared much worse!

The moral of the story here is to check a track car very carefully, and methodically, "as if" your life depended on it. Not preaching, mind you, as I am often guilty of checking the easy and obvious, while taking for granted other aspects since, after all, they've never let me down before ...foolish on my part to say the least. But as I had speculated in Simpatico's friend's similar incident on the street, metal fatigue sounds like the culprit. Which in my mind, raises another valuable reminder: check repairs/mods/impacts very closely.

Whether failure is due to misinstallation, poor fitment, or impact is anyone's guess (or determination), but metal subjected to stresses NOT factored into its design WILL give way ..."when" is anyone's guess.

Sorry, just musing aloud as I, too, track and drive daily these wonderful beasts. But as a reminder to myself and perhaps to anyone who cares to listen: check critical systems with a very critical eye ...as if your life depends on it. Drive in good health, all!

Edward