Hmm. Another plus for keeping t-bars on with the coilovers!

GC will make it right. Good luck.

 

I'm sorry to hear about that, man. If there's anything I can do, let me know.

If the stud is broken off flush, it can probably be removed by welding a nut onto the top.

Chad is right... The factory bolt on a factory shock doesn't actually support the weight of the car - the t-bars do that.

These aftermarket bolts rely on that shoulder being firmly planted against the control arm to support the load.

Not only should they be torqued properly, but you should also put a dot of paint on both the bolt and the control arm - this way you can do a visual inspection to see if they've moved any.

 

Glad to help. I still advise to talk with GC Tech support. Measure twice, cut once.

C.

 

Thanks for the information Chad, I wish I knew that it had to be torqued at 150ft lbs. I figured it would be stock unless they provided some information otherwise.

Yeah I usually put paint on every important or torqued bolt.. don't know why I didn't do it with these (or why I didn't check them since installing em..but then again I hardly drove it) but do you think its possible it somehow backed out and snapped or something? Only reason I doubt that is I installed the other side the exact same way and it is still firmly planted and 100% ok.

here is a pic.. I didn't get an underside cause its raining and I'm borrowing a friends really expensive digital camera. If its not raining tommorow (and I can work on it) I'll take a pic of the actual mount




excuse the dirty car.. I haven't washed it since it was vandalized. Now that its running I'll give it a good cleaning

 

the bolt doesn't lose any strengtth.

87951
95sl320 dd

 

"Setting" the bolt is important to prevent failure. Don't take my word for it. Read the materials I posted.

C.

 

Mike...call GC. I am positive they will help you. The speculation by all of us won't provide you with any answers.

C.

 

i read your reply, that's why i made the comment.

87951
95sl320 dd

 

Wrong one. I clarified with the post of the Racer's Edge materials. Please offer more info if you have it. I am sure it will help solve the problem at hand.

C.

 

Introduction:

My name is Jay from Ground Control.


The following are some unedited, unreviewed and quickly typed thoughts, and therefore may be slightly subject to change.

Here are my thoughts and experiences about these mounting studs. I have seen this stud design, from other companies, and not necessarily on 944s, break before. Everytime I have seen them break, they have not been tight, OR MORE CORRECTLY, were not engaged all the way into the hole. I have not seen this particular broken stud, but it will be easy to determine the actual cause. I am speculating that the cause was not being tightened until the stud shoulder was up against the arm, in turn causing the stud to bend downward and break. This is not necessarily the fault of the mechanic at all, and may lie in the fact that the threads in the 85.5-up control arms are inconsistent quality and depth.

I am speculating that the stud was tightened until it felt tight, which was not enough to seat the shoulder. I am in no way indicting the mechanic. More bolts have been broken with a torque wrench than without one, and I truly feel that this bolt was possibly tightened to an adequate torque, albeit by hand.----Wait, then how could it break if it was adequately torqued? I think the root cause is a false tightness, whether by hand or by torque wrench. Either method of tightening will give a false sense of security if the friction from the threads is enough to create resistance before the shoulder is adequately seated.

I am not familiar with the other 944 specific coilover studs out there, and I can only guess the reason for 150 foot/pounds torque would be to ensure the shoulder is well seated. I am only speculating about the reason for that high torque, so my recommendation has been 85 ft/lbs, which is industry standard for 14mm into aluminum and seems to concur with the factory.

This type of failure is very alarming to everyone, especially myself and the car owner (of course), so I intend to completely have the failure cause solved, and any changes in procedure publicized. Although I have not seen the actual part, I am confident in the material choice and treatment, but less confident in the procedure and mating part. As I stated in the second paragraph, I believe it is a procedural failure, and not a material failure.

I will post again when I see the broken parts, and will keep anyonne interested abreast of the news.

Thanks, Jay Morris

 

Great stuff Jay. Thanks for posting this.

C.

 

*ahem

My services needed? I'm cheap.

 

I think that this is good advice: ["so my recommendation has been 85 ft/lbs, which is industry standard for 14mm into aluminum] Bolt torque is based on a standard: bolt thickness and hardness and material it is threaded into. In this case the bolt is especially long (deep) which may allow for a higher torque.

 

Jay, from speculation as well, but I believe you will be correct. Due to the extension of the bolt to fit the coilover it is very important that the shoulder of the adapter has mated completely with the control arm. It would be possible to tightened the bolt until it feels tight, but it not be tight enough. It appears that at the proper torque the aluminum has slightly deformed creating a stronger bond between the bolt and control arm.

Without the proper deformation I would think that the adapter can vibrate, movement that would deform the surface of the control arm eventually loosening the bond between control arm and adapter, enough to prematurely fatigue the adapter.

 

I agree with Bill. However, I will also add that you are using the control arm in a way that it was not (to my knowledge) designed to be used, so expect s**t to happen. I'm sure Porsche over-designed the crap out of that part of the arm as a shock mount, but not to hold the weight of the rear of the car on heavy springs. In my opinion, even if the adapter is "seated" against the control arm surface, if there is not sufficient preload and any movement/flexure of the adapter is possible, then it will tend to deform the aluminum control arm surface, which makes more room for flexure and ultimately results in fatique of the adapter bolt.

Somebody should make those adapters out of titanium, and maybe this wouldn't be an issue. Or, send clear instructions on the 150 ft-lb torque requirement.