TD in DC

They say that the steel a-arms on '83-85.5 944s are generally safer than the aluminium a-arms on the later cars because they supposedly will not fail catastrophically like the aluminium arms. Well, my steel a-arm did.

Mine failed most likely because it was boxed improperly. Many "box" or reinforce the steel a-arms to prevent them from bending. The people who boxed mine for me most likely did so improperly. Specifically, they likely put too much heat into a-arm, which weakened the factory weld between the a-arm and the barrel that connects to the cross-member. Since they also did not put a reinforcing strap around the barrel, the barrel broke completely free from the a-arm when the factory welds let go.

Moral of the story? Be careful how you box your a-arms. Also, the complete boxing that you see is unnecessary and probably increased the chances that the heat from the welding would cause problems. All you really need are plates along the edges of the a-arm, which makes it appear sorta like an I-beam.

For those of you who haven't experienced an a-arm failure, you really don't want to. While I was driving, the steering wheel started to point slightly to the right. The car did not pull at all, and was driving absolutely fine. I pitted in, put the car up on jacks and started looking to see the problem. I couldn't see a thing wrong. So, I called over a couple of other friends, and they couldn't see anything either. We assumed that I had slightly bent something, but that nothing looked like it would fail. We couldn't be more wrong. During the next session (we were at Shenandoah Circuit), the car started shaking violently in the braking zone after the back straight coming up to the 180. I told my passenger, Nader, that we were going off. I eased off the brakes and the shaking eased up. We had scrubbed off enough speed that I thought we should at least try to make it, so I turned in. We made it just fine, and I coasted into the pits, which luckily wasn't that far away. Then, when I tried to drive the car up onto my trailer, the passenger front wheel fell off Just imagine what that would have been like if it had happened on the track . . .

In any event, here are the pictures of the failed a-arm.

Geoffrey

Wow, that is just plain UGLY!

TD in DC

Imagine how ugly it was to be driving when it failed

Geoffrey

"Imagine how ugly it was to be driving when it failed "

No Thanks, I'll pass.

TD in DC

That's why I want you to call me if and when you decide to sell your car.

KuHL 951

Anytime something is welded onto a pre-welded stamped part you have to take into account the heat affected zone of the new weld. You can reinforce them all you want but a good welder better be familiar with correct pre-heat; obviously this guy wasn't. What a shame.

Bri Bro

Scratch off one of your 9 lives. That was a timely failure to say the least.

Antonio

Without discounting the possibility of this being the result of welding heat related metal weakening, it appears to me from the pictures that what we have here is just plane metal fatique. I have a similar setup on mine. The part where the barrel meets the arm always struck me as rather weak looking. I doubt that Porsche had racing in mind when they designed it. How old was the arm that broke? How stiff is your front suspension? Have you noticed any tell tale signs on the other side?

TD in DC

The a-arms were less than 9 months old, and really did not have that many events on them. Although I do not know the exact spring stiffness of the front of my car, it is not stiffer than many/most 944 track cars out there. I removed both of these a-arms when the one failed, and I replaced with reinforced a-arms (not boxed like the one in the photo).

Russ Murphy

That was a brand new arm 9 months ago?

TD in DC

The a-arm was brand new about 9 months before the failure. The failure occurred several months ago. I saved the failed arm to take pictures to show others. I just got around to taking those pictures this past weekend. But yes, the a-arms were very new when the failure occurred.

M758

TD...
I used steel arms (un boxed) and have seen the metal crack in that area. That is why I have spare set in my parts box. The failure itself is normal metal fatigue and can happen on non boxed arms. It does appear that due to the considerable boxing this problem may have been made worse. Part of my daily inspections include checking these areas for cracks. I have found cracks on my stock parts many years ago and had been driving on the track with those cracks for a while. I replaced the arms at that time. More reciently I also had to replace an arm I replaced a couple years ago. Drivers side was cracking too. Never experiencd a failure, just the cracking only. For me given my inspection schedule and the low cost of the stock arms I am happy with these.

I do tend to think that the extreme boxing may have contributed to the failure. In fact the place the at needed support the most never got it with your arms. I would not be surprise if that alone made the problem worse. The rest of the arm was so stiff the ONLY place it could flex was in its weakest point. Result is an early failure.

tinman944

I would have to say you have other problems than heat...What did you have for bushings?
To me the photos look like something was binding up in your suspension.
I think Boxing the arms are a good idea.
1- something got lodged between the arm and the cross member.
2- bushings where to tight.
3- car set to low.coil spring bind.

924RACR

Oh my is that scary - glad to hear you got lucky on that.

Correct procedure for boxing the a-arms (per the factory) includes reinforcing that barrel. All the 933 a-arms I've seen had that wrapped as well. Likewise, when I went into the wall last with my unreinforced a-arms, it did start to tear there. Of course, it relieved most of the stress elsewhere - a well-engineered component, IMO.

Matt Marks

TD - 1st of all, nice manicure ;-

How come you didn't go to a charlie or fabcar or similar arm when you did the based on what you've seen with the OEM/boxed combination. These are clearly far better than the OEM setup - though they still can fail (pin failures)