Darren

I went to go lower my 996 with PSS9 installed -- currently the outside of the wheel arch is sitting about 1 1/4" higher than the rear tires -- and realized that I already have rubbing issues with how its sitting now. I'm running 265/315 MPSC, and I'm guessing that the increased grip of the wider rear tires has caused more suspension compression than I've had before.

There is a seam weld where 2 halves of the inner fender come together, right in the middle of the tire at the top of the arch. That has made a cut down the middle of both rear tires.

So my questions are:

1. Has anyone else had problems like this with the PSS9? The struts are supposed to have internal bump stops but that obviously isnt sufficient.

2. If I install some sort of external bump stop, what happens to the handling of the car when I bottom out on it?

3. For some reason, I'm still running factory sways -- do you think changing to GT3 sways alone would solve the problem?

Thanks.

Larry Herman

Gee Darren, I'm insulted that you didn't ask me on Sunday .

#1 - I don't know.

#2 - It gets ugly. Bottoming on the bump stops is for street use and Baha runs. On the track it causes immediate understeer (F) or oversteer (R) when you run out of suspension travel.

#3 - The GT3 sways are not much heavier then the stock bars, IIRC, but they are adjustable and so are very nice for final tuning. The proper way to limit wheel travel is through stiffer springs.

Darren

Unfortunately I didn't know then -- it was only from your comment of "Car looks good, now you need to lower it..." that I was out there working on it today...

I was also installing a set of these adjustable upper control arms:

Larry Herman

Looks sweet! Make sure that you remove the lower eccentrics, or at least turn them so that they are all the way inboard and can't shift under load.

Steve Weiner-Rennsport Systems

Hi:

Perhaps I can help;

1) PSS-9's are an OEM replacement sport shock system and do not permit the car to be lowered as much as a GT-3 or GT-2. The internal bump stops protect the adjusting mechanism as well as the floating piston that separates the fluid from the nitrogen chamber.
When a PSS-9-equipped car is excessively lowered, the shocks will bottom and then the spring rates leap to infinity; i.e. suddenly you are driving a Park Bench,.... Bottom line: you simply cannot lower the car as much as you might want.

2) Installing external bump stops will reduce existing suspension travel which is not recommended.

3) GT-3 adjustable swaybars are strongly reecommended for track use as those the primary tool for changing the understeer/oversteer balance of the car. These have nothing to do with suspension travel (or lack thereof).

If you want the car to sit lower and retain full suspension travel for proper handling, I'd suggest a set of Moton Clubsport struts & shocks with a custom spring package for your specific usage.

Just one person's opinion, of course.

JimB

Darren,
A couple of points. First, before you put those control arms on I would think real hard about what happens if one of them breaks in a high speed corner. I haven't heard of anyone having trouble with them but if it's my life and my car on the line I'd be going with motorsport or ERP parts rather than an import tuner turned Porsche supplier. At least have a look at the real race parts and compare their quality.

Second, and I know this won't be popular, but are you sure you want to be running tires that big. They are very tall, very wide and very heavy. I'd bet your car would be faster with a 235-285 combo. Maybe 235-295 at the most. Just a thought.

Third, I agree with Steve. I really like the PSS9s I have on my street car and I know many people are using them on the track with no problems but if you want to make the next suspension leap you should consider Moton CSs or something similar.

Just my 2 cents worth,
Jim

Darren

Thanks for the great feedback. The tires are about 11/16" taller overall than the stock tire height, so you are right that they are a little tall -- I'm rubbing about 1/8" on the top.

I know the 235/285 combo is more popular, what do they run on the cup cars though? The 235 doesnt seem to offer enough braking grip, the braking and turn in on the 265's is awesome. I'm just experimenting of course, I may find my lap times got worse.

Sounds like its time for the Moton's....

earlyapex

Darren,

Now is the time to ask yourself where do think you want this to go? You're about to spend allot of money getting a proper suspension. You will probably find that a properly tuned Moton suspension and alignment will get you much faster laps times than the street oriented (soft) PSS9's with wider tires. This may make your car unbearable on the street.

JimB

Cup car tires are tall but fairly narrow. Around 245/285 as I recall. Of course they are slicks. 996s in Grand Am Cup run 245/275 Hoosier spec tires. Most 996 club racers are using 245/295 or 315 Hoosiers but all of these cars have way more suspension than you do.

I haven't used MPSCs for a long time but I would be very surprised if 235s didn't have enough braking grip. If that is the case you might want to soften the front a little to let more weight shift forward. You might also try longer, lighter braking. 996s and especially 996s with soft suspension are much faster when you brake a little longer and always through turn-in.

I could be wrong. Just some ideas.
Jim