strandolph

Has anyone ever heard of something like this? This is a 944 rear trailing arm from a race car. I've been running solid bushings and mounts on the rear suspension for two seasons. Problem or coincidence? The front control arms failures are well documented, but I've never heard of this before. It happened on the turn-in to #1 at Summit Point. The resulting impact left me with with more than just a trailing arm to replace!

Steve

JET951

wow, i have never seen that before. it looks like a stress fracture. maybe a bad trailing arm? were you hitting the ripple strips at the time it snapped? of course solid bushing will transfer more of the impacts through the trailing arm, this in turn could and should shorten the life of the trailing arm and assosiated parts.
Sean

tinman944

I would start with spring rates. Either you are too soft and bottoming out...alot or way to hard.and there is no movement

Geoffrey

Or it sufferd fatigue, or it was a porous casting, or it took a hit in an accident, or, or, or.

tinman944

could be the wheel hit something.

M758

I have never seen that. I would guess it was either remants of crash damage or some sort of isolated material defect. I know no 944 spec has experience that and I don't believe I have seen that in even 500 hp 951's using 13" wide slicks. Concern has always been in the front

spazegun2213

wow, glad you are ok! and good luck with the repairs.

chrisp

do those move in 3 axis like 911 trailing arms? If so solid bushings are a bad idea.

Jason @ Paragon Products

I think by solid bushings he means spherical rather than rubber.

RedlineMan

Hmmmmmpf;

Yet another vote for steel.

By the looks of that, the break is completely clean and shows no sign of gradual deterioration. Many times when something fatigues and breaks, it will do so gradually, offering you a visual time line. You can see clean and dirty areas in the fractured surface that tip you as to where the failure started, and what was the last area to hold on. This one looks like a single incident clean failure. A porous casting indeed seems probable. That or some previous impact that you are unaware of.

strandolph

Yes... Altogether in the rear: spherical trailing arm bushings, solid torsion tube carrier bushings, solid torsion tube block mounts, 525 lb springs, Leda shocks, -2.5 degrees camber, 15x8" Fuchs, Tarret sway bar.

cooleyjb

I know of a 1978 928 that had a similar thing happen on the way home from a DE that it was being used in. About 10 miles after it left the track :eek

Bit of a background on it.

Around 500lb rear springs on it. Big sways. No accidents in the history of the car. Driven in DE's for the last 16 years with suspension slowly getting built up through the first 10.


BTW. Glad you are okay. Hope the car goes back together well.

BC

Was it the bottom front A-arm on the 928 or the rear K bar?

BC

Because the 928 has a steel rear K-Bar.

38D

Are you sure the t-arm broke before the impact? I've seen them break as a result of an impact, but never before.