pk951

I wonder if it weakens the spindle area where they remove 2mm of material to fit the 19mm balljoint?

Any failures with 19mm pin when that extra 2mm is bored out for the bigger pin?

Chris Prack

You are just delaying the inevitable. Enjoy your ball joints just spare us the "my ball joint failed and I trashed my car (long-ish)" thread.

Chris Prack

I have machined quite a few spindles for Charlie arms and have not had a single failure to date. I have seen the pin break but that was due to the incorrect bolt/nut being used as the pinch. It gets loose and allows the pin to "walk" in the spindle bore creating a stress riser on the pin and then a failure.

Olli Snellman

Two of my friends have had problems with thsese balljoints.They only lasted about 5000 km's (one summer).Cars are 951 & 944 n/a. Both cars are used on track and slalom events

Zero10

First you say that MMO will solve bad rod bearings, then you both trash ball joint rebuilding, and insult my thread titling in a single post?....
It must be nice to have money coming out your ears. Tell you what, buy me a new set of control arms and I'll install them and use them instead. Then you can feel all warm and fuzzy inside.



To those who have had constructive comments.......
Thanks. However I am starting to get confused.
It is mentioned that the ssi kit has a 17mm pin and that it's bad.
What size is the factory pin? I thought it was 17mm, and I don't recall ever hearing of them snapping.
Is the problem the material from which the aftermarket pins are made?

Looking at the Rennbay 19mm kit, the pin looks just as thin at the base (where the pin meets the ball). It seems to me that this is the weakest part, and is also under the most stress. How is the 19mm kit any better if this part is just as thin?
When the pins fail, do they snap where the pinch bolt goes in? Why would they snap there?

It seems that a lot of the failures I have read about are on dedicated track cars. I can only assume that the majority of these cars are lowered, and are running sticky tires. Perhaps this has more to do with the failure than the ball joint pin size? Or am I looking at it all wrong?

The last thing I want is to have a ball joint pin break while driving down the road. But there is no way I can afford $1300 for new control arms. I just bought a house, now I have more bills to pay, insurance to pay and I am still paying off my other car. $1300 is completely out of the question, and in my head unnecessary.

pk951

>Two of my friends have had problems with thsese balljoints.They only lasted about 5000 km's (one summer).Cars are 951 & 944 n/a. Both cars are used on track and slalom events<

Which ones the SSI or the Rennbay balljoint kit?

pete95zhn

Rennbay economy kit...I should have ordered that track kit in the first place,but everything else than those plastic parts were in good shape etc....and there was no warning about economy kit's unsuitability to occasional track use.
I've done about 3k mls since rebuild and now both upper plastic rings are shot. Race kit ordered.
BTW,that 3k mls includes 5 auto-x events and two track days,total about 80 2-mile laps.
I run MPS2's ( 235/35-18 ),front lowered but not violently.

SeaCay

Take the emotion out of and I think you'll see Chris' comments as constructive. Perhaps not the info you wanted, nor in the way you wanted to hear it, but it seems as if he's speaking the truth.

Chris: Are you machining the spindles for the Charlie arm 19mm pin yourself? I have a set of spindles that need machining and don't know of a decent machine shop I can trust.

Brian Morris

Zero10 -

The arnworx link gives a description of the SSI pin failing at the groove around the pin. This was at 100 mph - I assume on the track.

The link I gave to autobahnperformance.com shows the stock pin (I assume) shearing off at the bottom of the spindle attachment.

I didn't mean to imply that the SSI pin was any worse then the stock pin - it's not, it's the same. They're both 17mm. The stock ones are known to break on the track, hence the upgraded parts.

As far as failure analysis, here's my seat of pants take. Think about the forces going around a high g turn with sticky tires. Maybe on the track or autox. I go to a track that has a downhill turn with a bump that caused me to bottom out my M030 suspension while under heavy lateral g's. Given the right situation a significant amount of the cars weight is being applied laterally to the outside front tire. This force is acting like a lever on the hub->spindle. The ball joint (in general) being forced "in" and the top of the strut being forced out. I would thing the biggest stress would be right at where the spindle intersects the pin on the outside side. This would be a sharp line of force - this is where I would think the "sheared of at bottom" would start. The spindle is also causing tension on the inside of the pin, looking for a weak point - the groove. As far as the bottom of the pin I think the force is more generalized where you see the pin "neck down", there's not a sharp point or line of stress. The biggest point of stress is where the ball intersects the socket - and the most likely thing to give there is the cast aluminum socket (just a ridge) not steel ball.

The pins can shear off at the bottom, break at the groove, or bend. The ball can pull out of the socket. All of these things have happened. As far as I know only on the track.

You said you autcrossed 20-40 times so I assumed you wanted to fix it for good. It seems like you just want to get your car to drive OK on the street. The bronze cups seem like they better than the plastic cups. I guess if something happens at an autocross hopefully you won't hit anything. I wouldn't go on the track (that's just my opinion).

--Brian Morris
89 951

Chris Prack

Thanks SeaCay. Atleast someone can see the light....

SeaCay

No problem. Sometimes a disinterested observer is needed in these situations. I can see how he may have misconstrued your comments as being negative, I looked at them in a totally different manner however. Track car, with that many track days/events, needs something other than a factory arm with an unknown number of rebuilds. I'd like to think my well being was worth the $1600 for the arms, much less the value of the car.

Zero10

If you have seen my 951, calling it worth $1600 is questionable.
My well being however is valued slightly higher than the car, maybe $2k?

Everybody seems to like the 19mm pins. If I rebuilt with the Rennbay racing kit would everybody approve?
I can be certain that the control arm sockets are in good shape. The old ball joints had absolutely no play, and the arms and mounts show no signs of impact damage. My concern is only with the rebuild kits.
I am pretty sure I could have the machine work done locally and do the conversion for $400 or less including the new ball joints. $1600 is just not possible at this point in my life, and I don't agree that it is necessary. $400 is possible, just not right away.

Oddjob

I have seen several posts over the past several months, discussing premature failures of the the do-it-yourself rebuild kits. Seems like blame for the failures is being placed on either improper installation, or on damaged control arm sockets.

But with the mounting evidence showing that the kits may be marginal at best, I cant believe how many 'listers are still strongly recommending these kits, and how many are using these kits on track cars. Seems like a big risk to me, and one I would never take.

If you cant afford Charlie Arms (and many of us cannot), you can buy factory 968 M030 new arms for $800, and they will last a lot longer than what we are seeing out of any of the rebuild kits.

Ski

There is nothing that anyone is going to do for the ball jts if we all don't stay off the curbing at the tracks, me included.

Below is an email from well respected person in the P-car community:
17mm vs 19mm pin - Some feel the stock pin is too slender and is the weak point. I do not agree, failures I've seen occur at the base of the pin where it meets the ball, and that diameter is the same on 17mm and 19mm pins. The stock pin will break if the spindle clamping bolt is not torqued enough, as it is the clamping friction along the length of the entire pin that provides holding force, and not the bolt directly acting against the pin groove. I have seen spindle failure on cars drilled for the 19mm pins, and do not feel that is necessary or a good idea.

pk951

So the consensus seems to say, forget about the rebuild kits they won't last. Buy oem or aftermarket arms.