tom_993

I found the following on the tech section of PCA’s web site:

A few of these cars [1995’s] were criticized for a rear suspension anomaly that led in some cases to a loss of control. At the limit the rear of the car could go like a pendulum, and the only way to regain control was to let go of the steering wheel. Any attempts to correct with steering input would only fight its own attempt to auto-straighten. For 1996 Porsche introduced "minor suspension geometry changes" which completely solved the problem. This includes the rear camber and caster links, as well as the lower A-arm (control arm). The toe link was not changed but the toe bolts were. This change is not difficult for the shop, but it does require realignment for the kinematics.

The complete Q&A is here:
PCA Tech Section

There is a follow up here:
Follow Up

Does anyone know more about this problem? How big of a problem is it? Has anyone done the "fix?" How do you know if you have one of the “few?”

TIA,
Tom

DJF1

Thanks for bringing up on this board! Not long ago we had another thread discussing pretty much my comments from my track day with my "New" 1995 Carrera and the "wobbly" feeling I had. These articles along with some good advice from all these good folks here explain many things.
I too would of course be interested in this and if it is a "porsche fault" why would 1995 owners have to cough up the expence to correct it???

Hank Cohn

Tom_993:

That is an interesting article and an issue I have never heard before. I hope someone else comments on this information. I will be with a race mechanic this weekend and I’ll ask him about this.

DJF1:

Please point me to your earlier post about a wobbly car. If you mean that you feel the car jacking weight diagonally when taking a relatively long corner that is either up hill or down hill then that is pretty normal for a 993 with stock or even M030 suspension. A little more shock and spring will easily fix that. Is that what you experienced?

Hank Cohn

DJF1

Hank,

Please see the post "I need a 101 suspension education". Its a 2 page post now is located on page 3 of this board.
Then we discussed the "wobbly" feeling which I have conluded that my "new" 993 is in need of at least new shocks. Actually I'm going to upgrade completely since I'm at this stage. The wobbly refers to loading and unloading of the suspension while in a turn like the whole car diagonialy would compress and uncompress.Also what you described on long corners plus a two stage compression just as I thought this was the limit then the suspension would compress more .Certainly not as sure footed or linear as my old 968.

I hope I will be able to have my new suspension installed before the next DE event in March but should I address this with Porsche?? And by installing the PSS-9 which I'm planning to do will it cure the problem described in the article as posted by Tom???

Edward

I've had my '95 since May, use it as a daily driver (with, ahem, "spirited" driving), and have done two DEs with it so far and planning on Willow Springs this February. I have NOT experienced ANY of what the PCA Article alludes to.
Unless I misunderstood the Post and/or the article, and I just DE (no real racing), I'd have to say my 993 has in exceeded my expectations in every way, especially in the handling dept. Could it be that this "problem" is some freak anomoly? This sounds, by FAR, more rare than the Wiring Harness Issue (I'm still knocking on wood). Anyone have clarification in this because I'm really curious.

Edward

D.G.

I experienced this behavior in my '95 after I had the ROW M030 suspension installed. Strangely, as I recall it was worse with the M030 than it was with the stock suspension. I chalked it up to the poor allignment that was done when the M030 was installed. (long story)

Instead of fiddling with it, I had the M030 replaced with H&R coilovers and a 'proper' allignment and corner ballance done at another shop. The problem was completley solved.

I suspect the problem was caused by a combination of the weak rebound damping in the M030 shocks and improperly setup kinematic toe in.

When the suspension unloads following a bump in a long sweeper the suspension may travel farther than desirable. As the suspension travels the toe-in changes, and the two rear tires point in slightly different directions. As the weight shifts from one tire to the other the rear end shimmies back and forth.

D.G.

Doc Vorce

In 1997, I corresponded with Bruce Anderson about the retrofit of 18 inch wheels to a 1995 Carrera. He indicated that the changes made to the rear suspension of the 993 Carrera (beginning with the 1996 model year) allowed Porsche to fit 18 inch wheels to the Carrera and to standardize production across the 993 range. He never identified any "suspension anomaly" which served as the basis for the suspension changes.

Nevertheless, Reiser's claims about a "suspension anomaly" in the 1995 Carrera are interesting. I hope that any 1995 Carrera owners who have experienced problems with their cars' handling will post their experiences.

Jim Sullivan

My 1997 suffered from this anomoly, so maybe changes to the '96 were more to do with wheel fitment issues than addressing the shortcomings on the '95 C2 rear-end.

All 993's have "kinematic" toe adjustment which the factory provided to eliminate instability and oversteer.. it is supposed to help the tail thru a turn by avoiding toe out upon weighting , but if alignment is off or if your suspension is too soft with bad shocks, you will experience a marked bouncing around in the tail which several people have experienced at the track. Its a hinged or articulated feeling and very disconcerting. In my car, I would load the corner, and then if the car unloaded at all during transition, or upon exiting a corner, the tail would bounce back and forth from corner to corner for about 3 or 4 cycles before it settled down again.

It bears mention that my kinematic adjustment was correct when I experienced this, however I had stock shocks with stiffer H&R Springs and I do believe the shocks were not matched properly and with 20,000 miles they may have been weak. I upgraded to stiffer, properly matched shocks and springs and the problem went away completely.

Don Magee

When i bought my 95 used i noticed that it was not very stable during high speed sweepers. The car had been inspected prior to purchase and deemed perfect. The car was not wobbly in my mind-- it was more of loose feeling, but only on some turns. I had the car checked out and the right rear lower control arm was slightly bent, from being strapped down in transport I assume. After it was replaced, I have not experienced any inherent handling problems.

Edward

Just as I had suspected: not really a "flaw" or something that requires updating, but more likely symptoms of other rear suspension issues. Hopefully. Wheeew.

Edward

tom_993

Thanks everyone for the responses. Jim’s description of toe changes during weighting and un-weighting makes sense. It sounds similar to bump steer problems in the front. Since I’ve never experienced this feeling, and it seems pretty rare, I guess I can safely not worry about it. Like Edward said, “Whew!”

Tom

Ray Calvo

Surprising; I feel mine is very stable. The again, this si after drivng a modified '84 911 Turbo-Look (aftermarket bars and Bilstein Sport shocks). Times I don't feel comfortable I attribute to the tires (as in brand new street rubber).

Steve Weiner-Rennsport Systems

Hi Gents:

May I just jump in here for a moment and reiterate 2 things,.......

1) It simply cannot stressed enough how critical the rear static & kinematic toe settings are. Frankly, not very many places can do this competantly. The car will feel hinged or articulated if its not right on and this is very scary.

2) The rear suspension system of links and subframe is all bushed in rubber. As all rubber has hysteresis, this loads up and unloads in any corner and you feel this as a general "squishiness" depending upon how hard you drive and how sticky your tires are.

Although I am not necessarily advocating this, you should understand the dynamics of this and remember why the RSR has spherical bearings in all the link pivots and the subframe rubbers are replaced by the same things,... This ensures that all you feel in your hands and Gluteous Maximus are the tire contact patches.

Back to work,........