Skip

While there are a few choices out there to rebuild the already faulty design, the only real cure for safe lasting performance from control arms is to upgrade to aftermarket (at least 4 types now available) or simply do not lower and do not track. Of all the failures native to the 944, or any Porsche, ball joints are probably the most dangerous.

As I mentioned, there are expensive yet tested solutions to this problem. So, not to point out the obvious without proposing a solution, how about an idea for some entrepreneur to chase down. How hard is it to install a cassette bearing (high-misalignment spherical bushing) with hardened pin within the existing arm using circlips on both sides to allow easy removal. Just glancing in my catalog here I see there are such things readily available for ~$25/bearing and custom pin maybe ~$25/each. Add in development, profit and liability and were looking at ~$125/side upgrade. .75" pin (19mm) would require drilling the knuckle - as does the aftermarket solutions. Or, use the same 17mm size since the pin isn't really the problem. Good/bad idea? Wish I had time to figure it out... The trick is likely having to machine the control arms to make them a suitable receiver. Is there enough material to machine? Is the depth of the mount enough? Well, judging from what Markus has had to do with his upgrade arms, I would tend to say no - seems as though he would have already explored that opportunity.

Travis - sflraver

If you take a look at the basic components inside the OEM (aluminum arms) ball joint assemblies you will see some great design properties. They did not go with an insert cartridge, they built the joint into the arm. By doing this they were able to make allowances for a spring to be inserted below the lower ball joint cup. This spring, along with the plastic upper bushing, helps to create a barrier between the ball joint pin and the aluminum pocket. The wheel experiences a shock, its transmitted to the spindle... then ball joint pin... and its dispersed by the spring and bushings before the aluminum pocket even knows anything has changed much less starts to show any signs of stress fracture because of it.
Now that is all fine and dandy... as designed they work great.. but put 40'000 miles on a set of arms and we get a small problem. That plastic bushing cracks. Now being cracked it allows the hardened steel ball direct access to the aluminum pocket. This is not AS bad as it sounds except for you now have that lower spring working against you and not for you. You hit a bump, spring gives a bit, rebounds and knocks that steel ball into the aluminum. Its like taking a hammer to the inside of your ball joint pocket every time you hit a bump. Hit it enough and it cracks wide open. That is when things get dangerous.
As long as the bushings are kept up to snuff and they are made of a material that will take that "shock" without transmitting it directly to the aluminum pocket, there should never be a problem with them.

To address what skip is talking about with a spherical bearing design being put into an OEM aluminum arm, it is not a good idea. The ball joint pockets are not that thick to begin with and when you start milling on them it only makes them that much weaker. Now you go and mill them and then take away any shock dampening by placing a cartridge in there you are asking for trouble. Weather it be a febi joint or a spherical bearing... your still back to that hammer/pocket scenario.
Depending on how a complete aftermarket arm was designed, spherical bearings may be the way to go. The arm and ball joint/bearing holder would have to be able to take that direct stress.
As a matter of fact I believe mumzer has a nice design that has all of the physical requirements to take the stress of a solid joint. I am not sure if he is making any more right now but the ones he has made do look nice.

joseph mitro

KYB - Yyyyyyuuuuuucccckkkkkk!

those new shocks and helper springs look nice. what is the spring rate? I have 140lb helper springs on the KLA shocks on my car, with 275 lb front springs on paragon's ARHK. i think 300lb springs would easily be streetable. my car is fairly stiff, but not unbearable on the street. but then, i also like my cars fairly stiffly sprung, not squishy like my wife's PT cruiser.

Baron009

raised the car? *raises eyebrow*

Was it already lowered a lot? Cause mine is soooo low I thought about adjusting it sometime. But raising from stock.. I just don't get that.

MTM

From what I understand, the 968 M030 springs are 120 lb/in spring rate, but due to the geometry of the rear suspension they only add about 70 lb/in to the effective wheel rate. I believe the S2 torsion bars are slightly larger than the S, but your helper springs are stiffer than mine, so overall we probably have very similar rear spring rates. How well balanced is the handling with 275 lb/in front springs? With our setup, I've heard that 250 would be prone to oversteer at the limit and 300 would understeer.

It was at the stock ride height before, and the helper springs raised it up a bit in the rear. I am not planning on keeping it raised though.

Skip

That's one of the problems, yes. The other is actual binding which will simply rip the ball from its socket. Potayto, potahto - not guud.

That is exactly my fear. And the reason I state above that if it were possible someone, Markus for example, would have already done it.

Bummer, still - some classes don't even allow the aftermarket arms... and, for us 944na guys they cost nearly as much as the car!

Travis - sflraver

If the binding issue is the problem we have the geometry correction kits available. It gives you a longer ball pin which brings the arm back to is correct position on cars lowered up to 2" from stock. Gives the ball back its full range of motion without the binding issues.
Some people had some concerns with the strength of a longer ball pin but we have put a lot of time and money in R&D for the product. You wouldn't think so much time could go into 2 little ball pins.
What we have ended up with is a longer ball pin that is stronger than the OEM short pins. They are a one piece drop in and not a bolt on option.
Right now we have some being tested on track for PCA approval. Since you would still be using the stock arms and replacing just the ball pin with a redesigned piece, they would fall into a safety loop hole where they could be allowed. The perfect answer to running stock arms on a lowered car.

joseph mitro

the handling is pretty well balanced, and if anything oversteers a bit. but i also have the 19mm rear sway bar and 27mm front sway bar. i think it would be a bit more balanced with 30mm front.

there are other variables to consider, such as wheel width and offset, tire pressure, and driving style. with my (relatively) underpowered S, i like the car to oversteer a little bit, whereas with an S2, you might like just a little less oversteer.

Skip

Good to run it by PCA, but don't leave out NASA (944-spec, 944 Cup/Supercup) and SCCA (ITA/S).

Skip

Alright, Travis - looks like we swooped this thread

Sorry, folks - back on topic...

Not only do you want to correct your ride height, but you also want to preload the new coil-overs. You cannot get the correct ride height AND preload without indexing the bars.

Travis - sflraver

Isn't there a tutorial on Paragon about reindexing the T bars?

Skip

Yes, here: http://www.tech-session.com/kb/index...x_v2&id=66&c=4

and you should search for Joe Paluch's indexing guide here (soon to be on the tech-session site also)

Yabo

and btw.. kyb's are great shocks for the money. they are perfect for street driving i think. someone else also just said in anohter post that they are almost as stifff as konis, but alot cheaper. i have kyb's all around now and am very satisfied.