Mahler9th

I started DE driving and racing back in the 80's and 90's and have lots of personal experience with 944 family cars. This includes discussions/consultations with quite a few folks involved with these cars in professional racing. And quite a bit of experience and perspective on factory and aftermarket front control arms for these cars.

On my own cars, I ran factory arms, reinforced factory steel control arms (944), rebuilt factory arms (951S), Fabcar arms and I was the first customer to use Charlie arms. I stopped paying a lot of attention to this topic back in 2001 or so when I switched focus to 911 cars.

I occasionally run into newcomers that are focused on these cars and track DE and/or racing activities. Here is my age old advice to these folks:

1. Understand that there may be issues with factory arms and ball joints. At minimum, get informed, and best from folks with unquestioned experience, e.g., folks that have or had ties with pro racing.

2. Make sure your inspection regimen includes these parts.

3. Be aware that you may find (as I did 1987 - 2000) that no one can say which combinations of parts and set up circumstances may lead to sudden failures of factory parts. Porsche issued guidance on this in Panorama in 1995, but that guidance failed to match experiences of some, at least through 2000 which was the last time I checked.

4. If you have an early offset car, you may want to consider running steel control arms, reinforced via welding by someone that knows what they are doing.

5. The last time I checked, no one offered rebuilding of factory arms with new ball joints and made any guarantees of longevity. Street use, track use or any use.

6. Two outfits making aftermarket arms with significant professional experience were Fabcar Engineering (David Klym) and Wrightwood Racing (Charlie Arms). A third I would always check with is Racer's Edge (Karl Poetl).

So my question now is, what is the current state of affiairs on this topic?

I seem to run into people from time to time (like today at Partsheaven) that do DE and or racing in these cars and haven't a clue that there has ever been an issue. This includes a few 944 racers I encounter from time to time racing under NASA sanction.

Eric_Oz_S2

I am sure there are others with more experience, but what I do know is:

Charlie arms are no longer built
Racers edge make geometry correcting a arms
Fab car arms still available
Ball joint rebuild kits are available (and have worked for me on a track car for the last 4 years)
Most failures appear to be on lowered cars where a arms are inclined beyond horizontal.

I would also imagine constant kerb hopping and wide slick tyres wouldn't help things.

19mm ball joint kits available that require boring out of pin receiver

If I had a dedicated race car I would, however, consider one of the after market arms.

I'm sure others will fill in with more detail.

VaSteve

I bought a set from High Strung 944 last year. I have had them a year and they're pretty nice. They feature replaceable ball joints using the parts from the early cars.

pontifex4

Mahler took issue with this when I suggested it in another thread, as I recall, and I admit that I'm just some guy on the Internet, but this question does interest me.

Also, add the High Strung control arms to your list. I believe they are the least expensive, and like the Blaszak arms (no longer available) they can be made to take an early-style ball joint that just bolts on.

67King

Rennbay sells rebuild kits. Used to sell four varieties, but I don't see them all on the site right now. They were combinations of standard diameter and pin length, and oversized diameter and longer pins. I currently have the standard diameter, longer pin ones on my car, but I'm putting on Racer's Edge ones. Two 944's had control arm failures at Road Atlanta a few weeks ago. Had been planning on eventually putting on the Racer's Edge ones, but that sealed it. He's got some coming in this week, I'll get a pair from that batch. I'm a little paranoid about some things, that happens to be one of them. But I do think very highly of the Rennbay rebuild kits in the context of cost.

On the factory arms, there are two failure modes. One is the pin, itself, the other is the socket for the ball joint. Since the pin necks down, it is a stress point, it and often fails there. The picture on Rennbay's site does not show this, but I think his new pins no longer neck down all the way around, but intead just are scalloped. Makes installing harder since you now have to align them before you put in teh bolt, but gives more area, which should help. Minor inconvenience for more robustness is definately a worthy tradeoff IMHO.

The other failure mode is that the socket gets worn out on lowered cars. The way to fix this is with the longer pin, as it puts the arm on a less severe angle. Again, that's what is on my car, now. Had I known what I know now back then, I would have gone with the standard pin, increased diameter when I rebuilt mine.

That said, when you fix the issue that way, you create two different issues. First, you introduce bump steer. Longer pins lower the arms, but the tie rods don't move, so they are now at different angles. Bump steer can be corrected with spacers and different rod ends. The other issue is that when you do that, you change the roll center of the front of the car. On the front, that is nice, you get a bit more camber gain. But you can't fix the issue on the rear, you'd essentially have to relocate your pivot points - good luck.. So in addition to changing the roll center on the front, you've now changed the whole roll axis of the car.

I'm most familiar with the Racer's Edge ones, as (and also note full disclosure) Karl is my business partner with PRO. But there are a few things I like about them. First, they replace the ball joint with a threaded pin and spherical baring. You have to have your knuckle machined out, but the pin threads into it. On the arm end, I'm pretty sure that the pin goes all of the way through the spherical bearing. The others may allow this, I don't know (don't believe, though), but there isn't an issue with using the normal length pin on these arms to maintain your roll center. I do konw that he does make longer pins available, even though they aren't ideal, so they can be swapped out if anyone wants to play around with them.. Biggest downside is that they are HEAVY. Not cheap, either.

I don't think any of the others have redesigned ball joints the way teh RE ones do (i.e. change it out for a spherical bearing and pin). But I've heard nothing but great things about them. I personally really like the Charlie Arms, as I'm pretty sure they are aluminum, so they'd be lighter. But I don't believe they are around any more, so that's kind of a moot point.

Again, you didn't list the Rennbay kits, and for they money, they are a great option.

Mahler9th

Thanks for the perspective.

When I was informing myself about this, a spoke directly to people like David Klym, Jon Milledge and Charlie Spira. Folks with decades of racing experience and quite a bit of experience with these types of cars. I remember Charlie owned an Escort series or Rothman's car... but I digress.

I also spent nearly an entire day at Kelly Moss in '94 or so with David and Jeff Stone. It was a Saturday and they were very gracious. Pretty much just the three of us at the shop. They had strong ties with PMNA and PAG as they were running the 965 cars in IMSA and 944 and 968 cars in Firehawk in that period. While there I saw a lot of unique factory parts that most folks have never seen.

One thing I saw was a large collection of used aluminum control arms. They were Porsche Motorsports parts with non-replaceable ball joints. The pins were different from street car parts in that the groove was more of a slot-- it did not go around the entire circumference of the ball. This was not considered a sufficient enough design improvement to reduce or eliminate the need to toss the arms at regular intervals.

In some level of pro racing, I believe the Fabcar arms were required at some point in time. I am getting old so I probably don't remember everything accurately. I am sure a call to Dave Klym would clear that up.

I spent quite a bit of time on the phone with Charlie and John, and shipped my pins to Charlie after a certain number of track hours since he wanted post sales technical data.

I experienced two failures back in the day. The first was a late-offset arm with ~50k miles of street use. Pin sheered through the groove in AX.

The second was a 944 Turbo S arm. It had 32k miles of street use. I sent it out for a rebuild to a famous Porsche parts place in Texas. I did this because I felt it was a good investment that might be more cost effective for my situation than Fabcar arms (Charlie's weren't around at that time). These arms were as new with no signs of wear or issues.

Well, the first outing in the car, the ball pulled out of the arm. On track and at speed. ~$4k in damage, but driver (me) unhurt. Damaged bodywork. Damaged Fikse wheel. Damaged Koni double adjustable strut. Brake line ripped out (so I had no brakes).

I contacted the rebuilder because I was concerned about their quality/process control and as a Porsche fan and PCA member, I wanted to give them a heads up so maybe no one would get hurt.. I also expected them to perhaps take some responsibility. They did not

My lawyer had a car just like mine and was in mine the session or two before I had my failure, instructing my wife. The car was lower than factory height (but not on the deck-- it was my daily driver) and had modest springs and sway bars. My lawyer's car was set up essentially the same way. Yes, my car was repaired.

I wonder what would have happened if it failed at turn 10 at Sears Point and I got hurt or worse.

Anyway, I still have that arm and the ball. My friend, the late Jim Pashsa took some pictures and was going to write an article for Excellence but never got around to it.

Back in those days, no one had enough aggregate experience or data to say how low you could go or anything about sway bars, spring rates or wheel rates. Pro cars did all kinds of curb hopping and were in all kinds of wrecks. Porsche's note in Pano (which folks should read, I will see if i still have it) was pretty non-committal, and didn't match up with anecdotal failure reports I collected from all over. Most of this was collected by telephone.

I doubt whether anyone has done any organized info gathering in the decade+ that has gone by since last I checked on this. So I doubt a minimum ride height or other set up specs that "keep you safe" are known in any way.

I visited the Rennbay site. I have no idea why it should or shouldn't be technically better than what I had done back in 1995 or so by the parts company in Texas. There is no way that would be good enough for me. Dedicated DE/race car, or part time street/track car. Absolutely no way. The liability... well that risk would not be my cup of tea.

Before I got out of it, I bought and used some of Karl's stuff. And I spoke to him many times. I think he has accumulated a lot of experience. So I'd pick his arms or Klyms. Or maybe I could get Charlie to make me some. I would not consider any other products or approaches (except for reinforced steel parts on an early-offset car). I would especially rule out those products that were endorsed by "internet experts" and created and sold by folks that did not have professional experience.

Mahler9th

By the way, I think changing the rear pick up points on a 944 series car can be raised. Custom spring plates like I have seen on many 911s and a change to the attachment near the torsion bar tube a la 911. voila.

67King

You could change the banana arm point pretty easily, but the spring plate side will be a lot harder. Not sure how the custom spring plates look or do whatever they do, but you would have to change where it pivots. So it is the actual torsion bar tube/carrier, itself, dictates the pivot point, and not hte spring plate. I can't find it, but someone has actually gone in and change the spring plate over to a rod end system that mounts at the top of the torsion bar carrier.

By the way, now you've got me more paranoid than I was before!

comatb

My 1986 early offset car was built with re-inforced steel factory control arms. I felt that they would be sufficient with the g-forces on Toyo RA1's and they were. When I switched to the higher g-force Hoosier's I upgraded to the Racer's Edge arms. Their weight has the benefits of increased strength. They have been involved in impacts that bent and broke front suspension parts and they had no damage. I sent them back to Racer's Edge and they were checked in the manufacturing jig which confirmed that they were straight and true. They would be my first choice.

Mahler9th

A number of techniques from the MJ days of IMSA used on 911 cars (and 935s) could probably be used on 944 cars as well. It has been a while since I have studied the 944 torsion bar tube/spring plate design but if I recall correctly it is pretty close to the same as the 911 cars.

ERP has had a product for the latter for years. Tried and true. A number of others make and/or sell similar (copied?) units. I know of several 911 race cars with a customized version of this set up-- I don't think it is terribly hard to do. But you need to know what you are doing and have the budget to justify the $$ versus performance benefits.

I am sorry to alarm you 67 King. My concern is that the community is not as good as it once was in terms of making sure folks understand this. Even in my area, I have racer friends that took or take their chances on this. One had a failure at Sears Point a few years ago and was lucky he made it to the paddock. A seasoned veteran racer and DE instructor. Getting his car on the trailer was quite a project.

Likely Dave Klym's parts have the most accumulated DE/racing hours in the world. And I know for sure that Charlie's had the benefit of professional structural engineering and material science design considerations. And I fully trust Racer's Edge to be careful and meticulous in their process. After all, they take on quite a liability when they sell these parts.

And by the way, the lack of a clear understanding of parts combinations and set up parameters to which I have referred extends to tires and g forces as well. So back when I was involved, no one knew whether smaller and/or less sticky tires put you in a "safe zone." And I think that in general DOT tires now are even more grippy than what they ran in the 80's and early 90's when these cars were newer.

Mahler9th

There maybe some folks around from the old Rothman's days that remember what their experiences were like. However, I suspect that the general approach was to cycle out entire arms for new motorsport parts at regular intervals.

I have a video archive of all '87 and '88 Rothman's races. If I recall, there are a few examples of engine blow ups (#2 rod bearings?) with spectacular flame outs. But I cannot remember any instances of arm/balljoint failure in these televised races. But again, I suspect they just pitched the arms on a regular interval.

67King

You didn't really alarm me, just reinforced where I was. I had a friend with an IT-E Mustang break a suspension part which sent him off track at a really high speed, missing a wall by about 2 feet. I put a lot into my roll cage and fire system. I've only now gotten to the point of getting the remaining bits of the car as good. Had not considered control arms a safety item, but have gotten to that point.

So no need to apologize, and even if you had alarmed me, no need to apologize for moving my focus towards a safety related item.

951and944S

I have different take on this topic and was going to start a thread fresh back from TWS but got too tied up.

Our cars (all late offset with factory arms) race everything from PCA to NASA events and also a local series at Circuit Grand Bayou (formerly No Problem Raceway).

There are variables involved that might rule out a few causes of failure like, varying spring rates, different brand/valving on shock control, hinge point bushings from stock rubber to Racer's Edge type sphericals, etc.

CGB is VERY bumpy and undulating and the penalty for dropping one side wheels is pretty severe in a few spots....the type of sharp abrupt hits on the tire that would do in an a-arm or ball joint. We have done races there from 30 minute sprints all the way to 6 hour enduros without an arm or ball joint failure.

Here's where the twist comes in and what, in my opinion is part of the cause for at least the ball joint failures, it dawned on my as a possibility when my son snapped one (an aftermarket extended length pin) on the warm up lap at TWS on Friday, then later that same day, an SP2 snapped one (a factory length aftermarket pin from a different manufacturer) in the second session.

My son's car specifically, had just done a complete NASA weekend at NOLA, one of the smoothest tracks in the US, without as much as a tire off track, class win and runs at a pace fast enough to hold both configurations' track records for class so he's not putting around.

Why would he go from fast lap, race win, to popping a joint on a warm up lap weeks later at TWS...?

What's more, his car broke the opposite side in the same fashion, a couple of months before at NOLA..... coming off a race win and fast lap, off the track with no problem, right onto the trailer and into storage. The next pre-race inspection showed no signs of problems.

I tossed it off as metallurgy problems and even looked into the pin designs and noticed that somewhere along the line, the ones we use went from a circumferential groove all the way around the pin for lining up the spindle bolt, to just a simple groove on one side that makes you locate the pin correctly for the bolt to pass....this seemed like a strength improvement but it also was one that failed in the same fashion as the previous design.

So....at TWS on my friend's S2, I had already used up my spares on my son's SP2 car but we found a used factory spare arm to borrow from West Dillard.

He walks over to make sure it would work out and mentioned that he, himself had popped an aftermarket joint on a first lap too.

I never got around to check with West, so I hope he happens across this thread to give some input but just about to doze off for the night, laying in bed, it dawned on me.....,

I think it's the stress on the joints while towing that causes the pins to break.

Yes, all of our experiences are on track, but every time we have a ball joint fail, it's after a tow and all have been on opening warm up laps right off the trailer where the car was previously very fast, on differing tracks and checked out pre-event before loading on the trailer.

My theory is that for people who strap the fronts through a wheel opening, you are loading a lot of stress on the only movable part in the lower suspension....the ball joint.

Could be that the type of driving you do while towing could have an effect but you can't control those road surface spots where the trailer and tow vehicle bounce severely but it's my theory that it's mainly that you are tugging so hard with the straps to secure the car in a plane that stresses the joint, introduces a crack, and then it ultimately fails the first time around the circuit.

Just food for thought.....but our problems are so coincidental, and the conclusions so controlled, that I don't see how it could be anything else.

T

Van

Interesting theory. I follow your logic, but am surprised that the straps would exert a force stronger than maximum braking loads.

Do most people strap through the wheels? Or strap to the chassis?

951and944S

NA 944s....., who uses brakes....?

I kid though Van, but I guess it could be argued that the small amount of movement you'd get in the sphericals, delrin, factory rubber hinge point insulator would share the braking load, maybe even including the vertical leverage of the strut length and the way it's fastened top and bottom...?

There would also be the variable of weight transfer and it's effect on compression of the spring, hence different angular stress on the ball joint.

The strap theory, similar I guess to braking stress, difference being it is constant and not momentary.

I don't know if you have ever heard to do this or to not.....but we NEVER cross rear straps.

Same basic reason, that the load stress can change toe/camber settings on the rear of a torsion bar type rear suspension, especially if you have the rubber rear hinge point bushings still intact.

If you have ever replaced with the Elephant racing poly bronze types, you will have seen the evidence of the effect that just static weight of the car has on compressing these elliptically....so, same theory applies here in cross pulling your rear straps on a long tow.

When strapping on a tow, you are basically pulling the car apart at opposite ends for long durations and it seems the rough road trips where the car and trailer are bouncing a lot (car is still sprung with this method) would make the condition worse.

Dunno, just threw that out there since all of our failures have been right off the trailer on warm up laps that aren't even driven in anger.

T