BMW Strut tower distortion, cracking, & failures became enough of an issue that BMW engineers designed their own strut tower reinforcement plates (see above). Apparently this was an issue for E36, E46 M3's/ 3 series cars, & other models. BMW used light weight sheet metal in their strut tower construction, & deformation/deterioration occurred. These steel reinforcement plates were offered as part of the rough road package. BMW said the plates only had to be bolted on the underside of the strut tower mount, no bonding or welding required.


Deformed & cracked BMW strut tower above.

A Vorshlag tech describes how these things are used & modified if considering camber plates.


My car is currently stored in California & I live in Canada. Would anyone following this thread be willing/able to inspect & measure their GT4's strut tower underside to see if these may actually fit. If they fit flush & cover most of the underside surface, to walls of the hat, they at least will be stronger than the cast aluminum flat top.

 

Attached Images I showed failed strut tower photos to a mechanical engineer friend, along with Okie981's photos of regular Boxster strut/tower. The impression he had was the GT4 strut is failing ~ the inboard aft corner (top corner of middle photo). He said by taking measurements and utilizing Solidworks CAD program along with materials analysis info & program, the weak spots could be delineated. He also noted that the GT4 strut is more inboard & aft than the 981. He suspected the square corners of the mounting plate, are likely exceeding the stress tolerance of the tower support ribs. On the 981, the mount is round & larger. He suggested that if a steel plate piece was purpose machined, it ideally would extend to the curved ridge along the perimeter of GT4 mounting plate (see photos of strut mount on underside of tower). I also asked if a "generic" round steel plate would prevent the failure, & he thought it would decrease the likelihood, although not to the extent of an engineered purpose machined component.

 

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I dont think that the plates by themselves do much at all. these are supposed to transfer the impact on the shock tower to another stiffening member as a strut bar of cage. The pictures that I have seen of failure show that the problem is not one of incomplete spread of the load of impact but of insufficient structural integrity of the shock tower to absorb the impact. If you can transfer some of that load on to some other place (such as an extension of the roll cage to the shock tower) from the top plate, then, you have a greater margin before failure.

Jpr

 

We just saw our first one come through here yesterday.

 

Any details of what happened? Are you guys working on a possible preventative fix? :-)

 

More details are needed? A std OEM car or one of your modified ones?

 

pics of the failure would be awesome. based on previous pics i don't think there's a good safe guard yet that actually reinforces the whole top mount out to the sides....

 

 

^^
Thank you for sharing Buteo. It's a big repair on these cars.

Perhaps if this happens more often on other models as well, the impetus would be there, for our aftermarket friends to design something to prevent this potentially catastrophic suspension system failure.

 

The clubsport reinforcing plate may be there for other reasons. One reason could be that it provides a “soft” load spreading function of the compressive forces from the nuts. If the aluminum shock tower is high strength, then it will generally be more brittle (less flex) than weaker material. Brittle materials do not like cracks that could form from stress concentrations coming from the nuts. The steel could be softer than the aluminum as well.

It’s hard to imagine, but when the car is in dynamic motion, these parts all flex to some extent. It gets very complicated. Without the benefit of having detailed CAD/FEA models, it is unlikely any of us will get beyond educated guesstimates as to what is going on.

The find that the GT4 underside steel plate is different/smaller than the Boxter's, and does not seem to extend to contact an area that was meant to serve as the contact "patch" is significant IMO.

Someone asked if the cross-strut tower reinforcement might help and two posters said no. I agree it does not directly address the cause of the failure, but, we really do not know. Anything that transfers/reduces the loading or maybe even changes the nature of the loading *could* help. Or, heck, could make it more susceptible. If you had the failure while you had the stiffener installed, you bet Porsche would cry foul.

If you had a strut tower failure AND had added the clubsport reinforcement, will Porsche have more reason to deny the claim – “you changed the design of the car.”

Joe-->any fallout from your insurance company with the mega claim? These things go onto your CLUE report, and even when they are no-fault ("NF" on the report), the company (and underwriters reading it) still use that information to determine risk.

 

 

From what I've read in this thread here is that the chances that Porsche will step up are very slim to none. I wouldn't be surprised that your first pothole damage cracked it and didn't show upon cursory inspection. Further driving with normal road impacts probably caused the initial crack(s) to expand to what you are seeing now. In a way you are very lucky that no exterior panels were damaged that will require repainting.

 

Hmm. The number of strut tower failures is getting concerning. It is still only a fraction of reported 3rd gear failures, but as time goes on, we are seeing more of them...

 

Yeah, sorry to be a broken record, but this should have sticky status.