texasviany

I am not worried about that. I paid cash for the car and then converted it to a track car. (What manual?)

After researching, a softer spring allows a higher velocity of the traveling mass. So in theory, if the velocity of the weight is fast enough if/when the shock bottoms out, that would be more force applied to the strut mount than a stiffer sprung car that cannot bottom out.

okie981

And the 991 GT3 has the same spring/strut in front as the GT4 and the same shock tower as the 981 GT4/Boxster/Cayman. The 991 cars all have the same shock tower as the 981 cars, and the non-GT 991.1 and 991.2 Carreras have the same spring/strut mount as the 981 Boxster.

okie981

Post a photo of the top shock/strut mount or post a link to the part you installed on the JRZ website?

sharkster

Dammit this thread is not good. Never ever did we see this with 986/987/996/997 stuff in all the years sigh. Cost-saving and weight reduction done wrong

4carl

What about the 991 C4s? same?

okie981

I don't see a specific entry on this PET online menu for 991 C4 cars, so I have to assume they are the same as 991.1 and 991.2 Carreras. The 991 Turbo has the same shock tower so don't know why C4s would be different.

http://nemiga.com/cat_spares/pet/porsche/

okie981

There's a whole lot of information we don't have, but from what we see so far, it could be the 981/991 GT car camber plate size and shape combined with the monoball instead of bushing and what appears to be no bottoming snubber all are contributors to this failure mode.

If some failures other than caused by severe crash-like impacts are identified on non-GT cars, then the camber plate theory starts to fall apart. As someone in an earlier post noted, they saw a 981 Boxster S take a major impact that bent rims and the shock tower never failed. But are there any non-GT failures like Joe Weinstein's?

And as Spyerx pointed out, this could also be related to spring rates in the GT4s, especially if GT3 cars don't have these "normal" use failures like Joe Weinstein's, and the GT4 cars seem more affected.

And then there's the material quality control theory, also very credible due to variances in the aluminum die casting process.

We need help from Porsche to get to the bottom of this. If anyone has any pull or relevant contacts at Porsche, please raise this issue, and the 3rd gear failures also.

4carl

One thing that may contribute is the lower ride height of the GT4 compared to a reg 981 or 991. That means less room for compression of the shock before it bottoms out. Once it bottoms out all the force is transferred to the shock tower and thats a brittle piece. That in combination with no rubber bump stop on the shock rod may be the recipe for disaster.

Could something as simple as adding a short bump stop on the shock rod be a solution?? Does the GT3 have a bump stop on the shock rod??
carl

d00d

Thanks okie981 and others who are contributing to this thread.
On the face of it, when the GT strut top was designed to angle the compression direction to one side of the strut tower (and the rubber bushing removed), I would have expected Porsche to strengthen the strut tower to compensate.
Say you wanted to intentionally break the tower with a chisel, would you aim it on center, or would you go offset closer to an edge?

okie981

If anyone has photos of a disassembled shock, strut, and camber plate from any of the 981/991 cars, those would be helpful if posted here.

Just looking at the online PET, it doesn't look like the GT3 or GT4 have a bump stop, but I think there has to be something to prevent metal to metal bottoming.

I keep coming back to how so many of these 981/991 GT cars have been thrashed extensively with no shock tower failure. Then we have a few ugly failures. Weird.

Joe Weinstein, if you get the chance, peek up inside your passenger side shock tower with a bright light and see if you see any fatigue cracks or signs of stress. Maybe take a picture of it?

4carl

It may be a god idea to check the inside of the tower for cracks before and after a track day. Especially if you use the curbs or have an off.They would be easy to see. All you need to do is lift the wheel you dont really need to even remove the wheel. . I also checked under the shock rod dust cover for a bump stop, there isn't one!

Sorry for the orientation of the pictures i cant figure out how to rotate them .
carl

Spyerx

i'm sure there is an internal bump stop

Viperguy324

^ this.

4carl

Check out the images on this thread from the PET. There is one on the reg 981 not on the GT4. As i said last night i put my car in the air and lifted the boot around the shock rod and checked.
I guess its possible to have an internal bump stop but they never have used one on any PASM. car

Buteo

So how many of these failures have we seen? I've read a bit through the thread and have only found a couple...or am I missing some.