AndyT

I have seen the difference in the parts with my own 2 eyes they are clearly different. I have conveyed this message before and had not had a good reply.

Now on another 993 suspension note : My front lower control arm bushings on my TT turned out to be ground meat and the car did all sorts of weird stuff out at the Glen. I believe on person who drove the car's reactions when taking turn 2 in 5th gear was " WHAT THE F*CK WAS THAT !!!" So take a look at yours and see if there is a lot of play. I replaced with ERP monoballs. I dorve the car all season that way by the way. Just thought it was understeer. Not So. It was "No Steer"

jmreiser

RS Clubsport had yet a third set of parts, and should be free of this issue. I was referring to 1995 US models primarily as compared to 1996-1998 & Turbo. Sorry for the unstated assumption.

clubsport1

Cheers....I was being a bit of a smart **** ........Even so i am suprised having never heard about problems on '95 C2 cars before this thread.

RallyJon

I guess what I'm not understanding is how the suspension can only misbehave in 5th gear on the track. If you're at max cornering, how does the rear suspension know if you're doing 130 on the track or 40 in a parking lot?

Is it correct to say that at some point in the travel, under very high cornering loads, the stock suspension allows some toe-out when fully compressed?

And that is does this regardless of the static toe and the KT setting, no matter how conservative?

If this is true, how could it be anything other than a rubber/bushing problem?

Don Magee

Paging Dr. Reiser:
I searched the PCA tech articles and found the part number list, but I would like to get an estimate of the cost to do the update. I have a 95, with PSS-9s and have not noticed any handling issues at the limit(my limit is low, however). Nevertheless, this is an interesting issue and I might need to get this done.

jmreiser

The problem can happen in any gear, it is just easier to reproduce the problem at higher speeds. If you can get much above 1 or 1.2 g's in a parking lot, you should be able to cause this problem there too. One big difference is that usually we have stickier track tires on. If you used an autocross tire you should be able to achieve the same. But I have heard from people who can get it to happen with street tires on certain roads.

Normally a 993 without kinematics (according to Porsche) would tend to go towards toe-out on the outside rear wheel in a corner, which makes it go loose, and also goes towards toe-in on the other rear wheel. So the passive steering does the opposite. It tries to make the outside rear wheel toe in, and the inside rear wheel to go toe out. That is a good idea, and it works.

The issue is that it can get irritated, and start to rapidly swing from out to in and back again repeatedly. That is what catches most of us out. If you're a rally driver you may be able to shrug it off. Rumor is if you let go of the steering wheel it may fix itself. Or not. YMMV.

Good point. They may have also changed the formulation of the rubber and not said anything about it. All I could find in print was that they made "minor suspension geometry changes".

jmreiser

It would be best to get an estimate from whoever would or might be doing the work down there in TX. Roughly it's something just under $2k in parts, plus install and rear alignment. Whoever did your PSS9 install should be able to do it.

The rubber bushings on these parts are a wear item, and so are the ball joints. For awhile we thought about getting used parts to contain the cost, but it is really better to use new parts unless you can get some unusually fresh used ones. Also Porsche says to use new bolts and nuts for a lot of these. I sometimes don't, but you are supposed to.

What I am surprised at is that no one has yet tried to do this change by doing one pair of arms at a time. It may be that less parts would do the job. I haven't tried that.

Here are the part numbers and list prices.

1- 993.331.041.02 A-arm L $552
1- 993.331.042.02 A-arm R $552
2- 993.331.045.03 Kinematic link L&R, $214 each
2- 993.331.047.03 Camber link L&R, $227 each

List price $1986 total before any discounts, not including replacing any nuts or bolts.

Also check the toe links. I have seen some that were starting to get loose & sloppy at only 45k miles. If they are worn out, then replace them.

Phokaioglaukos

Thanks, Joel. I think I'm now beginning to understand this a bit.

Mark in Baltimore

I just had Chris Cervelli drive my car this weekend. Although he would like to see me fit ERP or Porsche Motorsports control arm monoballs and adjusting links in the rear suspension (not the camber plates), he didn't think that the handling was disastrous in the least, and he's very picky about car set-up.

Joel, I have never felt the back and forth that you describe with my Moton-equipped, late model build '95 (or even with my old PSS-9's but I was a slower driver two years ago). When I'm really pushing it at high speeds, the back end may come out, but it comes out in a fairly benign manner that can be easily checked with a bit of opposite lock. I'm not saying it doesn't exist in other '95's; I simply haven't felt it in my car and wonder if it can be attributed to updated pieces? I'm an okay driver who is working hard at taking my driving to the next level so I can run with the class-dominating 964 cups.

jmreiser

Under compression the tendency is toe-out on the outside rear wheel, and by design the kinematics pulls it back in. The problem occurs due to either a bump, or a sudden lift off the throttle, or braking, in the corner. This transition from squat to dive is what I believe sets it off. I think you can see how the suspension can get confused as to what it should do. I don't know how or even if they fixed it, I just never heard of anyone reproducing or experiencing this problem after that. So I infer that they fixed it, but I cannot prove it.

jmreiser

Hey Mark- Sounds good. Motons are great, and also that implies you've lowered the car quite a bit. Lowering really helps with this problem. The Motons may even be helping control the suspension. Chris is great, if he says it's fine then it's fine. I can't argue with his recommended changes for a race car, absolutely. The stock parts above are what we would use on a street-driven car. The ERP or PMNA stuff can be driven on the street by the brave, but more maintenance may be needed.

TheOtherEric

I respect subjective opinions, but a more rigorous review is needed before concluding that this $3000+ mod is "an absolute necessity for the track, and is close to that on a street driven car." Impugning an entire 911 model year based on subjective butt-readings of a few people (paying customers?) is premature. Some questions that would need to be addressed are:

1. What was PAG's intent when they redesigned the parts? Joel says it was due to instability, and that may be true, but has it been confirmed? Did PAG issue any TSBs or other explanatory info? If it's really THAT serious, wouldn't we hear something from PAG?

2. Which arms were lengthened/shortened? All of them?

3. What's the general effect of the geometry change? For example, to cause more kinematic toe effect. Or whatever. Does it even affect KT behavior?

4. Can we mimic the update without replacing all the parts? For example, just replace one or two arms. Or different alignment specs.

5. How can we conclude that it's ok to change all the parts EXCEPT the subframe? Did PAG say it's ok? To play devil's advocate, I'll argue that by implementing half the fix, you make the handling worse. Prove me wrong... please.

You're not saying that 1995 993's lack the kinematic toe effect, are you? Otherwise I can't see the relevance of the KT discussion. Are you saying that the KT effect was changed in the 1996 part changes?

On a side note- Joel, thanks for getting involved in the discussion. Many of us are very interested in the topic.

jimbo3

Anyone have an idea at what point the 1996's have the updated parts? Mine has a build date 9/05 and the last four of the VIN is 0553- do I have the updated items? (It's going to be awhile before I can get under the car again.)

TIA
-Jim

jmreiser

Apology requested. They were not paying customers. They were friends and people I met through PCA.

Mark in Baltimore

Thanks for the info, Joel. Do you think my car might have the updated arms/pieces?

Oh, in my last post I added that I never felt the issue with my PSS-9's and RS ride height, but I was a slower driver back then. If there was a problem at high speeds with the Bilsteins, it was due to too much rear bar causing an inability to apply the power at high speeds, in addition to a driver/reaction issues.

Our time with Chris was just incredible. What a great coach and incisive mechanic...