Darren

I was on my way to work this morning, and suddenly the steering wheel on my 996 goes about 20' to the left. I limped it back home and was very suprised to find that the strut shaft sheared off right under the monoballs.

The car sits fairly low, PSS9 set on stiff, TRG monoballs. My assumption was/is that the monoball was somehow binding and causing the shaft to fatigue until it eventually broke.

Has anyone seen a failure like this before? I know I'm a little extreme running the monoballs on the street, but it seemed necessary since I kept ripping through the stock upper strut mounts.

What the heck do I do now? If I put another strut in I'd expect the same failure to occur eventually.

The monoball hammered away at the snap ring. There is a bit of surface rust on the bottom of the joint, but doesn't seem to be binding. The joint itself moves smoothly but stiffer than it should be.

Here are some pics:

Van

So, you've had it break a few times? Always the same side?

I bet the top of your spring hat isn't allowing enough movement of that monoball... The spring hat might be hitting the bearing mount, and then the strut tries to move more which causes that shaft to bend/flex a little below the hat (about where it broke). After a number of cycles, the material work hardens, develps a stress crack, and then breaks.

Darren

I never broke the strut shaft before, I've broken several stock upper strut mounts, i.e. the rubber rips out because of the increased stress of stiffer springs.

Great idea about the spring hat, I'll have to take a closer look at that and see if it may be binding. Hopefully I can buy a single strut someplace...

Cory M

Bilstein motorsports in Poway CA can probably rebuild your shocks and replace the failed shaft for less than the price of a new one.

reno808

i would use better bolts than those. They are all rusty

Jarez Mifkin

Atleast it didn't happen on track.

Darren

Yeah I probably should have used the gold plated grade 10 instead of the crappy grade 8, I'm cheap that way.

GaryAZ

Darren - What do you think is the reason this was happening? You wouldn't expect this to happen with Pss9s. If I recall you were running extra wide tires on all four corners. Could this be contributing excessive stress on the struts?

NJ-GT

A picture of the spring hat could provide the answer. It seems like that hat has lateral movement against the strut top (camber plate).

chris walrod

I dont see why the snap ring is starting to fail since it only experiences load at droop. Could you post some pics of the shaft showing the failure?

Van

That's why I think the spring hat is hitting something, then letting the strut shaft act like a lever. The movement (and force) that snapped the strut is probably one-and-the-same that bent the snap ring... Normally that snap ring should see very little force - but the deformation tells another story.

KRA993tt

I did this also 2 or 3 times. I was breaking my right rear each time. I raised the car up to Euro spec ride height and that fixed the problem. This was on a 993TT with Pss9's. Something about the geometry of the suspension. The car had camber plates/monoballs as well. My fix came based on the advise from Steve Weiner. Hope this helps.