Hi everyone,
I have a 996.2 Carrera with original X51 engine and light weight deletion options from factory. Its suspension has these following mods and alignment:
PSS10 setting Front 4 & Rear 5
Tarret Engineer control arms and links mimicking GT3 suspension, adjustable sway bars, car is lower
Front: 2.2 neg camber, 8.0 pos caster, 0 toe
Rear: 1.8 neg camber, 3/32" toe in
Front rim 8.5 in with 235/40/18 Pilot SuperSport 31 PSI
Rear rim 10.5 in with 285/35/18 Pilot SuperSport 33 PSI

My question is what I can do to the suspension to cure the unstable swaying movement at the rear when the car at high speed and change direction and my input to the steering wheel is constant, smooth and not abrupt. In general, the rear is not inspired confidence.
Appreciate your input,
George

 

I attach pictures of rear tires to give more clues.

 

New tires will very likely fix your problem.

 

Squeaky,
Do you know why there is the uneven wear on the tires?
Thanks

 

It’s hard to tell from that angle if the wear is even; you’ll need a full shot of the entire tread and both sides of the shoulder.

if it’s the tire damage your asking about, it would depend on what you were doing.

 

Squeaky,
Thank you for answering my question. My question about tires maybe unclear. In the posted pictures, they show the difference wear at the outside edges of the right and left rear tires. The inside and middle of both rear tires are normal wear and the same. I'm suspecting that maybe some suspension bushings are bad. I'm driving the car at high spirit pace, but trying to be smooth at the throttle. The tires are old and have a lot of tread left. Car has very low mileage at 25K and previous owner did not drive the car at all.
TIA.

 

Afaict, that’s not wear, it’s damage. It’s happening cuz your tires are old.

edit: a factor is also the weather conditions you drove it in.

 

Ok, that's an easy fix then.
Thanks

 

As for why it’s happening on the right and not the left, it could be a number of reasons - like how you were driving, where you were driving, road conditions, weather, what exactly you were doing, etc.

or simply, maybe it just hasn’t happened to the left side yet.

 

it should “fix” the loose rear end, but again, weather conditions are an important factor. There maybe other causes as well (such as your sway bar settings - though I doubt you’re close enough to the limit during spirited driving for that to matter) but road worthy tires should be your first step.

 

Squeaky,
I hope that you don't mind that I dig in this discussion further. In dry condition and bumpy road with PSS10 front 4, rear 5 settings, the rear is unstable and swaying. I know that the old rubber is harden and has not much grip on the edge. But the swaying action must come from the sway bar setting too soft. Am I right? The sway bar is GT3 sway bar.
Thanks.

 

No problem.

I don’t really know what you mean by swaying... and again, it depends on exactly what you are doing, but yes the damper settings can be a part of it, but it also depends on spring rates, roll resistance, ride heights, tire pressures, among 5000 other things. Ultimately it comes down to the roll rate distribution, but like I said before, by your line of questioning, I doubt you’re near the limit of the car for the above factors to matter materially. Which leads me to the tires...

The tires are a problem for sure, and there’s no point in adjusting anything else if those tires are on the car, that is why I said replace those and see how if the problem remains in warm, dry conditions.

 

Sqeaky,
I thought it would be an easy solution for all my problems. I'm not technical in car settings, but have lots of bikes on track. Swaying means unwanted body roll in the car in the turn and over bumps. You are right about the tires, that must be changed first. Do u have a lot of track experience with Porsche?
Thanks

 

Everyone,
I'm assuming that the PSS10 doesn't have custom valving, oil and spring rate specs from Bilstein. I felt like the PSS10 doesn't soak up bumps very well, it is either too hard or too soft. I love Ohlins on bikes and heard good things about them on Porsche too. Do you know any shop that is specialized in tuning these PSS10 with the right oil, valves, and spring rate in SoCal?
Thanks

 

I don’t know much about bikes - all my experience has been with cars.

for cars, it rolls as a whole, so the rear doesn’t really roll (or sway) “more” than the front, save for some frame/bushing flex. What do you mean by unwanted body roll? As in it rolls too much?

With Porsches, I have a 3 or 4 years of track experience.