That's what I did.

http://www.tarett.com/items/996-997-...-ea-detail.htm

....and for good measure I did these:

http://www.tarett.com/items/996-997-...smt-detail.htm

From reading the archives I came to the conclusion that these pieces (along with the toe links) contribute the most to preventing unwanted rear tire alignment changes. My butt-meter isn't sensitive enough to tell exactly what's going on, but after one track day so far I did notice that my car feels much more stable. My lap times haven't changed because I don't push it that hard at my local track (too much concrete), but the car feels better out there. More sure footed. A couple times the tires started to let go around a corner and the car was easy to catch. No surprises.

Tightening things up back there seems to be a great way to reduce the excitement level at the track.

Cheers,

 

Guys, anyone know which bushing I'd have to replace with a monoball to get rid of a slight rear weight shift when the car is fully loading up in a corner. Feels like the car suddenly steps out a touch at the back, but its actually a bush flexing my instructor has told me.

 

Hard to say, I think we need some more description.

Possibles are the lower control arm (main arm) inboard bushings.

 

Not sure I can describe it better. It doesn't happen on all corners, but on some where the load is progressively built up but to a high level (longer high speed corners generally), it feels like the car lurches a bit at the rear. Car is on intrax 4 way dampers although it did it before on stock, and the intrax introduced solid top mounts, but otherwise its just standard 6 RS suspension parts all round.

I think the instructor even told me which bush it was but I've forgotten. He mentioned his early cup car used to do the same, but Porsche removed the bush at some point in the cups evolution and when they fitted the new parts it went away. He also mentioned that it might take a battering on the road and wear out which is why I wasn't paying as much attention as I should. I have a monoballed e36 m3 which had some of its joints ruined just by driving it from London to the ring (via Belgium which has the worst roadd in a developed country!), so didn't want to make my RS as vulnerable.

I only ever really get the symptom on one corner at Silverstone GP circuit (Copse). Did have some of the eccentrics replaced recently though, so be interesting to see whether they were slipping and causing it as I didn't feel the same issue at Spa which has some corners I'd have expected to exhibit the issue.

 

It’s hard for me to say what’s contributing to this “lurching” feeling. Austin may know. I can say that if you’re running the stock toe links, you should change them to either the standard length adjustable or the bump and length adjustable ones. Either one will eliminate the rubber bushing in the stock link. This is the #1 suspension improvement you can do to the GT3. You’ll be very happy with the results.

Ira

 

Thanks. Are there any negatives to this change in terms of extra maintenance or wear? I live in the UK and drive to the circuit rather than trailer and it can be wet.

 

Dan, what AllanJ did to his car is probably the basic suspension improvement the 6gt3 needs. And he lives in Vancouver (no stranger to rain) and drives his car to the track.

 

I have not had any problems with putting the toe links and mono ball in the rear. I also drive -200 miles - to one of our tracks.

 

Good reviving this.. My car has been so finicky with holding alignment recently, I was going to just add the F/R toe links but figure there is more to the equation , could it be worn bushings as well?

 

Dan,
As long as the rod ends are good quality and properly sized, there shouldn’t be any maintenance or wear issues. Dirt hasn’t seamed to be a problem, but there are boots that can be purchased to seal out dirt.

Ira

 

Dan are you on the stock toe links?

OMG! I just re-read and it sounds like you're on the stock toe links and you track you car with race dampers?! If so, what kind of a mechanic or engineer has allowed this to take place? If not, then we can do some more trouble shooting.

When I first read and you said you're on RS components, I for whatever reason thought RS as in R, RS, RSR Le Mans cars. We just don't have 996RS' here so I rarely think about that term in street car version. Thus I figured the only rubber bushings you still had were the top dog-bones or the center pucks on the lower control arms, which were edited during the evolution.

For anyone running rubber toe links, it's a must to replace them with spherical bearing before you take your car out on the track again, for your safety and everyone elses. Pay the $495 US for monoball and thread adjustable links, or buy $900 bump steer adjustable ones. You can always replace the rod ends or ball joint ends after they're expired (way down the road).

With the stock rubber pieces, your alignment is changing toe settings under load, then springing back to a different setting altogether.

Dan I promise you, regarding toe arms, if they're high quality and installed correctly you will not have any extra road noise or vibration, the car will feel much better.

I'd also recommend the RSR main control arms, at least for the rear of the car anyway.

 

Hi Austin,

As you surmise, my car is a road going 996 RS. The dampers are 4 way, but the control graph and spring rates are setup around MPSC tyres rather than slicks. Why do you feel its dangerous to run without changing the toe links?

To be honest, I'm not familiar with what all the parts you are referring to are and some of the US terminology is different too. Am I right in thinking the toe links attach the bottom of the right to the chassis mount, and these are the parts which have an eccentric adjuster on the chassis side.

This then leaves me not knowing what dogbones, lower control arms are?

Anyway thanks for the advice it is appreciated.

 

Hey Dan, here's the abridged summary on the suspension pieces of your car's rear:


1. Main control arm: aka lower control arm, the largest suspension member arm. It bolts to the subrame and travels outward at 90 degrees from the subframe. On the end it has a ball joint which the wheel carrier (upright) sits on. In the middle it has a bushing that the "thrust arm" bolts to. This bushing is frequently called the "puck" since it's about the size and shape of a hockey puck.

2. Thrust arm: aka trailing arm, or "tuning fork" for the certain note it produces when struck while not attached to the car is the longest suspension arm. It bolts to the main control arm and travels at a 45 degree angle (approx) towards the front of the car where it is secured to the unibody.

3. Toe Arm: aka track rod or rear tie rod. This arm is the furthest to the back of the car. It bolts to the subframe and to the wheel carrier, almost parallel with the main control arm. It's noticeably thinner and at the subframe is secured with an eccentric bolt. The toe arm controls how much rear toe you have, if the wheels point inward or outward. The stock arm has a rubber bushing which is soft and causes the rear wheels to change toe under load. It's just my opinion that this makes for danger, because giving the rear wheels the right to steer the vehicle any which way w/o driver control brings risk to an already daring activity.

4. Upper Control Arms: aka Dog Bones, they look like the stereotypical bones you would see dogs in cartoons carrying around. They're fat on either end where the bolts and bushings are, and more narrow between ends. There are 4 of these per car (2 on each rear wheel carrier), and they attach the top of the wheel carrier to the subframe. GT3, RS, and Cup Car each have the rubber bushed ones, but some people change out to R, RS, RSR components with spherical bearings.

At the beginning of this thread there is a parts film snap shot showing pieces of the arms that make up the lower (the upper dog bones aren't shown), if you check it out and use the notes I wrote here, it might gel quite well.

Let me know if I can answer any specific questions, I will do my best to help.

Austin

 

AWESOME post, I need some components asap!

 

Got the new links from Tarret yesterday. Installing them Wednesday by a local shop. I'm also letting them do the bump steer fix trick people were saying in the other thread by reversing the bolt upside down.