Droops83

Just wanted to post this as a warning.

I run a mostly stock '86 951 in POC events, in the "J Improved" or JI class, which only allows upgraded sway bars, shocks, and bushings as suspension mods; springs must remain stock, which makes for a soft car. I have Tarett sway bars, which are great, but should not be used with factory cast aluminum front control arms, especially with stock springs.

I had run the original A-arms with the Tarett bars for about a year and a half (~2 weekend-long track events a month) with no problems. I noticed slight play in the ball joints last year, and after looking at the price of new factory arms and aftermarket options, decided to try the rebuild option with bronze bushings. After a few events, they had play again (sockets were worn out), bit the bullet and bought new factory arms, since they were still less than half as much as Racer's Edge, or even used Charley arms.

During the 3rd run session on the 1st day of a 3 day time trial event at Laguna Seca this past weekend, the left front arm broke during hard braking into turn 11, which is the very tight last turn onto the main straight. Luckily it decided to break then, and not in turn 8, 9, or 10, which would have likely put me into a wall and caused serious damage.

While the arm broke during braking in a straight line, looking at where it broke, it looks like the stress was likely caused by the swaybar. The car felt great through turn 10, and I was gaining on a slow driver who was driving a fast 997.2 GT3 on slicks (I was on street tires ;-).

I was pissed at first as this was a newer factory part, date stamped 2006, only used for about 6 months and a few track events, but after thinking about it, very hard track track use on stock springs and a stiff sway bar (it does all the work) is a pretty big ask on a cast aluminum piece, especially if the metallurgy is not as good as it used to be (the original ones never had a problem with the Tarett bars like I mentioned).

Luckily, I was able to find a 944 Spec racer in the paddock who had a spare early steel arm that I was able to put on and limp home, instead of a $750+ tow. The drive was not fun because the left front shock also blew during the incident, which made big bumps on the freeway a hair-raising experience. Also, the left front fender got damaged from the wheel folding under

I think I am going to park the car for now, save my coins for real control arms and springs, and in the meantime get my stillborn 944 Spec car going. I have loved the fact that I have been able to drive my street car and my only car to and from the track the last 3 1/2 years and get away with it (and have learned to drive the hell out of it and keep up with some theoretically way faster cars), but my luck just ran out.

My warning is: I would not trust factory arms with racing swaybars and heavy track use, and not only because of the well-documented ball joint issues.

JJK78

Damn glad you are ok. That is crazy, i've never seen it.

Van

Some JB weld will fix that right up!

I may have a set of Fabcar arms for sale in a few weeks.

rlm328

There is a lot of discolored metal there, is something else going on to increase brittleness. What does the breal look like side on? Is it shiney across the entire break or does it look dull in places like it was a more gradual break. Maybe more than one explanation.

Just from the pictures it looks like a long term fatigue issue and not an acute problem.

Oddjob

Weltmeister bars were also known to bust A-arms on occasion, but only heard of it happening on 85.5 and 86 cars - unfortunately seems likely that the 86 arms are somewhat weaker than 87+ arms.

Does the tarrett bar mount and pivot the same as a stock bar? Are all the mounts and bushings solid. That A-arm mount sure looks rigid.

A-arms and the stock sway bar do not pivot in the same planes of motion. So there needs to be some flexible mounts and bushings to allow rotational movement of the swaybar relative to the control arm. If the bushings are solid and triangulated brackets are added to the swaybar frame mounts, the swaybar and A-arm motion will bind, putting a lot of stress on the swaybar mounts to the frame rails and the swaybar mounts on the A-arms. This will be worse with stock springs, because the body roll is greater, A-arm movement is greater, and more load carried by the swaybar - so binding is much more likely inducing very high stress in the cast alum A-arm.

Best way to confirm freedom of movement would be to lift the front of the car, pull the struts and push an A-arm up and down to see if the swaybar binds or restricts movement of the arms.

Probably best to use a factory 30mm bar w/ the stock rubber bushings.

VWaddict

Hey Van,

What do I need to check on the Fabcar arms? -I have a set on my car, and I've heard mumblings about "pins", but I'm a little vague on what that means, or how to check them.

I know you'll know, because you're so thorough, as well as much smarter than me!

Van

LOL.

If you can afford it, replace the pins every few years. I thought Fabcar had a website, but I can't find it now... But here's their contact info: http://www.facebook.com/pages/Fabcar...69246719752883

It's more of an issue on frequently used race cars, but there have been cases of pins sheering. (Of course that happens on stock control arms, too.)

But, also remember that the original Fabcar arms were made for cars likes these:





Which, if you have....

vette951s

I second what Jim says about Weltmeister/stiff sway bars /soft stock springs causing failures with pins / control arms, having seen these failures at the track - especially with "rebuilt" factory arms. I also second what Van says about Fabcar pin failures. I converted my race cars, including my Cup car, to Charlie arms without issue.
Another failure prone area on '86 951 cars are the front spindles - I've seen two of these fail on the track, one right in front of me going into turn six at Laguna (lucky there was no serious damage). I would seriously consider updating to late spindles while changing to Charlie arms.

Good luck! John

samluke

I used to run the factory arms and sheared a pin many years ago. I have used Fabcar ever since. The Fabcar pins are larger than the factory, where the pin becomes the ball, but can still fail. I have seen a couple break. I had one of mine break as I backed into the culdesac going at very slow speed. I checked the other and it was about to let go also.

I had heard folklore regarding Fabcar Titanium pins, but never did confirm if real or old wives tale.

They generally crack/fail at the root of the parallel section. Dye penetrant, or magflux or similar inspection will detect onset of cracking. Fabcar pins are fairly easy to remove. I carry a couple of spares to the track. Hopefully I will never have to use them.

You can install larger diameter Fabcar pins, but then you have to machine the spindle to accept them. Machining the spindles takes meat out of them. I have seen modified spindles fail instead of the pins, and spindles are much more expensive to repair, especially if its TurboS/MO30.

If your running short/early arms, you could run the steel ones and then beef those up.

As others have said, that's an unusual failure, and the only thing that looks different is the sway bar arrangement.

Oddjob

I think OG Racing is the sole distributer for Fabcar A-arms.

http://www.ogracing.com/catalog/2-Ca...NG-CONTROL-ARM
http://www.ogracing.com/pages/Search...hedWord=fabcar

I have used fabcar arms for 5 years. Just replaced a pin this summer as a precaution after contact w/ a wall. Hard enough hit to bend the shock body, so didn't want to worry about the pin. But after removing, the old one looked fine so its in the tool box as a spare.

jmj951

I always get nervous when I see posts like these. I'm running factory control arms with an M030 front sway bar, and I ran on Laguna Seca several times, and will be moving back in November to run several more, so maybe I'll see you in December or early next year.

I haven't seen this before, and the cause is not directly obvious. The way the a-arm broke, it looks like the drop-link could not fully pivot on the a-arm and forced it to bend in the middle, but if you look at the design (for others, see a pic of this installed at https://rennlist.com/forums/944-turb...tructions.html), it doesn't seem possible that it could bind due to the way the drop-link bushings are designed.

Here's a reference from Tarrett's web site that interested me:

SAFETY NOTE: The factory 944 front control arms made before 1987 are known to fail catastrophically, even under street driving conditions. Porsche redesigned them in 1987 to resolve the problem. Using the earlier arms in competition and/or with other competition components will likely increase the stress on them and further increase the chances of their failure. We highly recommend either replacing them with a reliable aftermarket design, or having them properly reinforced, or inspecting them for cracks before EVERY race session.
http://www.tarett.com/items/944-seri...sba-detail.htm

BTW: Compare the attitude of our cars through the corkscrew. Too bad you have to run stock springs.

chrenan

I run the Blaszak arms on my car, the stock ones always made me nervous.

I liked the steel arms on my 924 much more. I used to have them seam welded as well.

Droops83

I remember reading the warning on the Tarett site, but never had a problem with my original arms, and I checked them regularly, and checked these newer arms (remember I put them on ~6 months ago and they are date stamped 2006) right before the event, no sign of stress or cracks. I will admit that I did not check them after the first couple sessions of the day, right before it broke, but I felt no reason to.

I'll post some more detailed pics of the break when I get back to my shop, the break is not perfectly clean, and it does appear to be due to brittleness.

If you look at the link that jmj951 posted to the Tarett site, it shows a pic of the bar. It uses a much thicker, beefier version of a factory-style center bracket, and a rear triangulation bracket that ties into the subframe bolt, like the KLA brace for the factory bar. The center bushings are solid with urethane inserts, and the red A-arm mount shown in the pic is certainly solid. I did spend a lot of time playing with the drop links to ensure that there was no pre-load or binding throughout the range of travel. I previously had problems with breaking the center brackets, usually from impact damage from hitting a dip on the street or a curb on the track (they would get bent from the impact and break fairly soon after that from the resultant binding); I solved this by cutting off the bottom inch or so of the brackets so they do not hang as low. This mounts the swaybar higher as well, so is only possible if you have eliminated the A/C compressor like I have.

Bottom line is, I knew that I was running a compromised setup by keeping the stock springs and depending on swaybars for almost all of my anti-roll; that is not what they are for. But, both financial and class decisions ("JI" in the POC was a very competitive class until this year when most of the competition moved to different cars) and the fact that it was a street car driven on crappy roads, all kept me on the stock springs longer than I should have. The upside is that I have learned to drive the crap out of the thing and I can keep up with cars that I should have no right to given how soft the car is and how little grip it has on 225/16 street tires all around. The downside is illustrated in the pic, and I have learned my lesson, luckily with no other consequences than a bent fender and an expensive weekend without much running.

BTW jmj951, my avatar pic is from my first ever event at Laguna a few years back, when it was TRULY stock with stock swaybars and everything. It still rolls like a pig with the Tarett bars and lowered in the rear, but not quite as much as in that pic. I ran M030 968 bars for a bit, but the car understeered like a pig, even with the rear bar full stiff. I even tore the left side center mount bracket out of the frame at Buttonwillow once when I was running those bars. I came across a good used set of Tarett bars about a year and half ago and have been running them ever since and the car handled way better with the extra adjustability/less slop and binding, but as we all now know should really only be used with better arms/springs.

azbanks

FIFY

DanR 1201

If your rules allow it or you're unconcerned about them, change the drop link design. Instead of connecting it to the control arm connect the link to the strut. Make sure it's long enough to turn with the strut without binding or severe angulation.

There'll be no stress on the control arm from a roll bar and/or no more unsprung weight from added strengthening gussets etc. Another benefit will be the extra roll stiffness due to the change in mechanical advantage. IE a lighter bar could be used for the same roll stiffness or a heavier bar without considering how compliant the bushes are.