kurtkrum

I recently installed some RSS suspension parts, specifically the eccentric lockout, rear tow links with bump, and the upper control arms (the dog bones). I also got a Kussumaul alignment. I did all of this to make the car feel more planted on the track. The car is new to me and I have only had it on the track one weekend, where I found that the car is less stable/planted than my old 996 C4S.

Now with the suspension mods and Kussumaul alignment, the car gets twitchy. If I am hard on the gas or hard on the brake it seems fine. But when I am cruising along at say 45 MPH on the road with little gas or no break (i.e., neutral input on the car) it becomes very unstable in the rear.

Is this normal for this type of setup? I am a novice and new to this, so I am wondering if this is the price I pay for turning this into a track car or if this is atypical.

Any help is much appreciated. I want to be safe on my next track day

996FLT6

So stable on the track but not so on the street? Sounds normal to me. So at 45mph what does it do? Is this on a straightline or turn? You're LSD is ok? Mike

kurtkrum

Since the new suspension bits have gone it and the alignment was done I have not yet taken it on the track. I experienced the twitchy behavior on the road in a straight line.

The LSD was replace with a new guard unit about 3 months ago...so no LSD worries.

Thanks for the help and guidance

996FLT6

So in a straightline wo brake or has what does it do? It's dry asphalt surface rt? Mike

kurtkrum

Yes dry asphalt. After the suspension and alignment work, I drove it home and noticed on the road that the car wanders and is twitchy at the rear under relaxed driving. When I accelerate hard or brake firmly it doesn't seem unstable.

Gofishracing

check rear toe- make sure everything is tightened down. Dead shock?

Serge944

Did you also change the thrust arm bushings to solid aluminum pucks? If you use anything but the center hole, the rear suspensions gets very twitchy. I learned the hard way with my 996.

In another unrelated occurrence, I had one of my lower control arm nuts back out (at the ball joint), which caused my rear end to be unstable while cruising (not under load). Check all fasteners.

996FLT6

How's the toe upfront ? I have negative toe wanders like crazy. Mike

mjb

I'm betting rear toe needs readjusting. These cars can be a little "twitchy" on roads in general, especially if you're toed out a bit in the front. But the rear should not feel twitchy or wander if everything is in order.
If the toe in the rear is really out of adjustment it will be very noticeable back there. Happened to me and it was nearly undriveable.

tgavem

It may just do what this car does. The 996 is a very capable track car, and with the changes you have done, it gives it very precise steering and direct response to input, either from you or the road. In my gt3, no answering the phone, grab a drink etc during road driving as every little input from me or the road will move it one lane over.
Therefore, take it on a smooth track and see if same twitchy behavior. If not, car is good.
On normal road, full attention to the car. Now you have an excuse to your wife/girlfriend why you can't answer her calls. You are welcome :-)

Recommended set up here, zero toe in front, 0.15-0.2 neg in rear.

mooty

BINGO

otherwise your alignment is off.

kurtkrum

OK - I am ordering pucks tonight LOL.

My first track day on these new goodies is March 9th. I will upgrade my thrust arm bushings and then hit the track. I will also have my instructor drive the car since I am such a novice.

I really appreciate all the help folks!

LVDell

If you were closer or come to Raleigh, give me a shout and I'll go for a spin with you. The car should feel insanely planted on both track and street with the proper alignment, ride height, all all properly functioning components. The only caveat I would say is that with a more track focused alignment, you will feel a bit more wandering on the street at non-agressive straight line driving. But it should NOT feel twitchy. My guess is a botched alignment (most probably rear toe), something loose, or tires that are not true.

cfjan

Why would that be if adjusted correctly? The thrust arm bushings allow one to adjust to the caster and if anything, with the additional caster, the car should be more stable..

452gt3

Have you checked that the tires are thee proper match front to back, this can also make it drive poorly.