944 family aluminum control arms and ball joints: what is state of the situation?
04-08-2013, 12:23 PM
#17
Race Car
The wear points are insulated by fixed materials even if you have spherical inserts.
It was recommended to have the arms x-rayed or otherwise checked for cracks in the event that a car left a road surface on street or track but I have never seen a fatigue "life expectancy" ever mentioned.
There was a factory bulletin that would pay parts and labor for replacements somewhere around 1987 but I don't remember the details.
I bought a low mile, dealer maintained '87 944T that had this recall done and it had the late 968 arms installed.
What do you think about the trailer strap theory Travis...?
T
04-08-2013, 12:24 PM
#18
Race Car
FWIW, the failures I referenced at Road Atlanta were late on the second day. don't know if either guy anchors the wheels of chassis. Anecdotally, most failures are the pin, which doesn't fit with the fatigue opinion. socket failure seems to be from stress that exceeds design spec from an extreme angle. I don't have one on front of me, but my recollection is that the failure did not look like most fatigue failures.
04-08-2013, 01:01 PM
#19
Rennlist Member
Are most pin failures at the point where the spherical ball transitions to the shaft? Or at the notch for the pinch bolt? Or a straight shear across the pin right under the spindle?
I have rebuilt a number of aluminum arms with the Rennbay kits, and I'm always amazed but the poor condition of the plastic "socket" that goes above the ball. They're always crumbling away - even if the joint doesn't exhibit any play while shaking a wheel on a lift (but, of course, I can't put 1G of cornering force on the wheel when I shake it by hand - not even when I eat my spinach).
I'd have to think the degradation of the plastic socket plays a role in a situation where the pocket fails.
04-08-2013, 01:16 PM
#20
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The tow strap idea is interesting. It would be hard to say for sure if it is the cause of the failure or just one more stress factor that adds to the failure.
With a pin fracture you have two distinct modes of failure. First you have a incident failure where a single instance (off track, hit a wall, etc.. ) will cause the pin to fail. From my experience and feedback over the life span of our parts, the majority of the time this will cause the pin to actually bend. Only in extreme circumstances will it cause the pin to completely sheer.
The other mode of failure, which is more common, is a pin fatigue failure. This is a cumulative failure that can be caused by many different factors, and this is where the wheel strap towing starts to sound like a bad idea. That off track excursion you had, after another race you found that your camber bolt was loose, that time you blew out a tire trying to get one more DE session out of a used up set of R-compounds. Each one of these can cause the pin to flex, then return to its original shape. Much like bending a paper clip back and forth, each one of these flex incidents brings the pin itself closer to a fatigue failure.
A lot of our track customers are replacing the pins after every known incident as well as at the beginning of each season in order to deal with pin fatigue. We find that with the solid bushing kits, all other components can be retained inside the joint when swapping the pins as part of an annual track prep maintenance. And yes, we do offer single replacement components to our customers at a discount to meet their track maintenance needs in order to bring costs down when replacing these parts.
In a perfect world we would all have 24mm pins attached to spindles with enough meat around the pinch to accommodate them. In an even more perfect world we would have both upper and lower control arms. But, like a lot of things, the cars are what they are. We work within the boundaries of the design to make them as reliable and safe as possible.
With a pin fracture you have two distinct modes of failure. First you have a incident failure where a single instance (off track, hit a wall, etc.. ) will cause the pin to fail. From my experience and feedback over the life span of our parts, the majority of the time this will cause the pin to actually bend. Only in extreme circumstances will it cause the pin to completely sheer.
The other mode of failure, which is more common, is a pin fatigue failure. This is a cumulative failure that can be caused by many different factors, and this is where the wheel strap towing starts to sound like a bad idea. That off track excursion you had, after another race you found that your camber bolt was loose, that time you blew out a tire trying to get one more DE session out of a used up set of R-compounds. Each one of these can cause the pin to flex, then return to its original shape. Much like bending a paper clip back and forth, each one of these flex incidents brings the pin itself closer to a fatigue failure.
A lot of our track customers are replacing the pins after every known incident as well as at the beginning of each season in order to deal with pin fatigue. We find that with the solid bushing kits, all other components can be retained inside the joint when swapping the pins as part of an annual track prep maintenance. And yes, we do offer single replacement components to our customers at a discount to meet their track maintenance needs in order to bring costs down when replacing these parts.
In a perfect world we would all have 24mm pins attached to spindles with enough meat around the pinch to accommodate them. In an even more perfect world we would have both upper and lower control arms. But, like a lot of things, the cars are what they are. We work within the boundaries of the design to make them as reliable and safe as possible.
04-08-2013, 01:21 PM
#21
Race Car
I don't cross at the rear, but do strap to the wheels. I've always thought that if you strap to the chassis, the tension in the straps will vary more as the car/trailer goes over bumps. Strap to the wheels, and the loading is more "steady".
Are most pin failures at the point where the spherical ball transitions to the shaft? Or at the notch for the pinch bolt? Or a straight shear across the pin right under the spindle?
I have rebuilt a number of aluminum arms with the Rennbay kits, and I'm always amazed but the poor condition of the plastic "socket" that goes above the ball. They're always crumbling away - even if the joint doesn't exhibit any play while shaking a wheel on a lift (but, of course, I can't put 1G of cornering force on the wheel when I shake it by hand - not even when I eat my spinach).
I'd have to think the degradation of the plastic socket plays a role in a situation where the pocket fails.
Are most pin failures at the point where the spherical ball transitions to the shaft? Or at the notch for the pinch bolt? Or a straight shear across the pin right under the spindle?
I have rebuilt a number of aluminum arms with the Rennbay kits, and I'm always amazed but the poor condition of the plastic "socket" that goes above the ball. They're always crumbling away - even if the joint doesn't exhibit any play while shaking a wheel on a lift (but, of course, I can't put 1G of cornering force on the wheel when I shake it by hand - not even when I eat my spinach).
I'd have to think the degradation of the plastic socket plays a role in a situation where the pocket fails.
The failures we have seen is a straight across shear right under the spindle but on close inspection on 1-2 of them, they looked to have maybe been compromised already and then the rest of the material gave up the ghost on the warm up laps. This is what made me think of the trailering load because the cars go from full tilt boogie with no problem, a cool down lap (not much stress) then loaded right onto the trailer, checked, then trailered again for the next race.
I always use a prybar to get between the bottom of the spindle and use the arm for pivot leverage to exercise the free play up and down when checking....for the exact reasons you stated...., no amount of spinach is going to Popeye enough force by hand...
Maybe the answer is to go with the 19mm pin diameter and bore the spindle.
I never have because I figured you are only moving the potential for failure to another location when you try and strengthen something.
T
04-08-2013, 01:32 PM
#22
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Fabcar Arms
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.
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.
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Your Source For Motorsports Equipment
WWW.OGRACING.COM
800.934.9112
703.430.3303
info@ogracing.com
Sparco's Largest Distributor for 28 Years
PFC Distributor for 27 Years
Pagid, Alpinestars, MOMO, OMP, Hawk, Bell, Aim, G-Force, HJC,
HANS, Arai, Simpson, Brey Krause, Longacre, CoolShirt!
Supplying Track Junkies for 34 Years.
PCA Club Racing - National Sponsor Since 1998
A Veteran Owned Business
Check out our blog!
04-08-2013, 01:42 PM
#23
Three Wheelin'
Thread Starter
As I mentioned, I stopped being proactive on this topic when I sold my 951 back in 2002. At the time, it had the first customer set of Charlie Arms, with about 16k street miles and maybe 15 two-driver track events and a few races. Charlie analyzed the pins after about the first 10 hours if I recall correctly.
My less-than-thorough, non-scientfic perspective gathering suggested to me that there were no concrete answers beyond what I described previously.
Interestingly, between my two failures (a period of a few weeks), my lawyer/friend had a pin fail under braking in the corkscrew at Laguna Seca. He was carrying a passenger, another friend/951 driver. They did not hit anything, thank goodness. At the time, his arms were used Fabcar units that had used pins. There were some theories that the pins he had obtained were not authentic Fabcar units, but I don't know if there was ever a conclusion.
So when all of this happened I called Jon Milledge back East. He told me of the project he and Charlie and others were working on with FEA/pro engineering and material science. But the arms were not yet available for customers. So I got in line for the first commercial set and bought a set of Dave Klym's arm for the interim period of several months. Once Jon had my arms had drop shipped, I sold my Fabcar arms and installed the Charlie arms. Jerry Woods was kind enough to bore my spindles.
I think the towing "theory" is interesting, but somehow I doubt there is any singular cause/effect on these parts, whether original street car parts, motorsport parts or aftermarket parts. I don't think the aggregate experienced in the decade+ since I last checked has converged on anything specific.
Of course plenty of businesses may have cropped up selling and supporting alternative arms and/or ball joint replacement kits in the last decade+. Kudos to those that are taking a serious technical approach and keeping an eye on things. And standing behind their customers.
The reason I started this thread is that I fear the community has lost a bit of focus on this in terms of informing newcomers to learn the basics and make decisions appropriate for their circumstances. I think you can get hurt or killed if your aluminum street car ball joints fail on the street or on the track. Same for aftermarket parts.
And it scares me when I read internet comments like: "Those parts look nice," or "those parts are much cheaper." What I'd want to know is whether they work.
My less-than-thorough, non-scientfic perspective gathering suggested to me that there were no concrete answers beyond what I described previously.
Interestingly, between my two failures (a period of a few weeks), my lawyer/friend had a pin fail under braking in the corkscrew at Laguna Seca. He was carrying a passenger, another friend/951 driver. They did not hit anything, thank goodness. At the time, his arms were used Fabcar units that had used pins. There were some theories that the pins he had obtained were not authentic Fabcar units, but I don't know if there was ever a conclusion.
So when all of this happened I called Jon Milledge back East. He told me of the project he and Charlie and others were working on with FEA/pro engineering and material science. But the arms were not yet available for customers. So I got in line for the first commercial set and bought a set of Dave Klym's arm for the interim period of several months. Once Jon had my arms had drop shipped, I sold my Fabcar arms and installed the Charlie arms. Jerry Woods was kind enough to bore my spindles.
I think the towing "theory" is interesting, but somehow I doubt there is any singular cause/effect on these parts, whether original street car parts, motorsport parts or aftermarket parts. I don't think the aggregate experienced in the decade+ since I last checked has converged on anything specific.
Of course plenty of businesses may have cropped up selling and supporting alternative arms and/or ball joint replacement kits in the last decade+. Kudos to those that are taking a serious technical approach and keeping an eye on things. And standing behind their customers.
The reason I started this thread is that I fear the community has lost a bit of focus on this in terms of informing newcomers to learn the basics and make decisions appropriate for their circumstances. I think you can get hurt or killed if your aluminum street car ball joints fail on the street or on the track. Same for aftermarket parts.
And it scares me when I read internet comments like: "Those parts look nice," or "those parts are much cheaper." What I'd want to know is whether they work.
04-08-2013, 01:44 PM
#24
Three Wheelin'
Originally Posted by pontifex4
;10365270...like the Blaszak arms (no longer available) they can be made to take an early-style ball joint that just bolts on.
04-08-2013, 01:47 PM
#25
Three Wheelin'
Thread Starter
As a side note, I bought my Fabcar arms from OG Racing (Bill). I think it is quite possible that their geographical area (Potomac Region PCA I think), saw more 944 family cars in amateur track use in those days than any other. Thanks to companies like OG Racing, Fabcar, Jon Milledge Engineering, Wrightwood Racing, Racers Edge and newer companies for helping us with these things.
I feel less supportive of companies like the one in Texas that made an obvious mistake rebuilding my 951S arms and did not stand up. And maybe put others at risk.
I feel less supportive of companies like the one in Texas that made an obvious mistake rebuilding my 951S arms and did not stand up. And maybe put others at risk.
04-08-2013, 01:54 PM
#26
Three Wheelin'
Thread Starter
Oh and I guess one more side note... hopefully the community is also still informing newcomers about potential spindle failures and potential cast alu wheel failures with these cars.
They are excellent cars, don't get me wrong. But I think it is helpful for new folks to know about these things, and I suspect that the demographics related to age and budget have created a bit of a knowledge gap on this stuff.
They are excellent cars, don't get me wrong. But I think it is helpful for new folks to know about these things, and I suspect that the demographics related to age and budget have created a bit of a knowledge gap on this stuff.
04-08-2013, 02:31 PM
#27
Interesting discussion. I have a SP2 car that has been raced for years. It has Blazzak arms with the early ball joints. I have them inspected regularly. I have had one failure of a pin (on turn-in, T10 Watkin's Glen). This is the first that I have heard the towing theory. I can see how crossing the straps would put some extra pressure, but enough to cause a failure? It seems that off roading or a very rough track would be much greater a problem.
04-08-2013, 02:38 PM
#28
Rennlist Member
First pic is the failed spindle - it was bored too large (3/4" instead of 19mm??) and it was also bored at a "straight angle".
The bore is at a slight angle, so I machined a set of aluminum blocks to hold it. I also set it up in the mill with a 17mm "blank" to make sure the axis are lined up properly. I also put a shim into the slit, to make sure it was machined with the correct gap. And make sure you use a reamer and not a drill bit. And I also used a counter sink to chamfer the edge.
04-08-2013, 02:42 PM
#29
I had my 3rd pin breakage at the TWS CR. I finally realized, after a tip in a Rennlist thread, that my spindle was slightly damaged. The pin hole was out of round by less than a millimeter, but enough to allow some movement of the lower half of the pin which fatigued the pin at the pinch bolt. I suspect this happened when I tried a longer pin, and I did not realize it, going on to break 2 regular length pins.
Changing spindles.
Van - we posted at same time. Great info. That is exactly why I plan to replace spindles rather than just boring my damaged one.
On the main topic - I tow with the strap around the front control arm. Been meaning to get something easier to get to.
West
Changing spindles.
Van - we posted at same time. Great info. That is exactly why I plan to replace spindles rather than just boring my damaged one.
On the main topic - I tow with the strap around the front control arm. Been meaning to get something easier to get to.
West
Last edited by Weston Dillard; 04-08-2013 at 02:50 PM. Reason: Overlapping responses
04-08-2013, 02:53 PM
#30
Three Wheelin'
Thread Starter
That spindle picture is scary.
My spindles were from a low mileage 944 Turbo S street car. I installed them on my '87 944 Turbo (which I bought from IndyCar racer Randy Lewis) along with all of the other 944 Turbo S suspension stuff. Of course I later went much further in that suspension development.
Anyway, when I asked Jon whether I should open up the spindle holes myself, he recommended his friend/colleague Jerry Woods. I am pretty sure the two of them conferred by telephone.
Hopefully not too many people are mis- or underinformed on this topic.
My spindles were from a low mileage 944 Turbo S street car. I installed them on my '87 944 Turbo (which I bought from IndyCar racer Randy Lewis) along with all of the other 944 Turbo S suspension stuff. Of course I later went much further in that suspension development.
Anyway, when I asked Jon whether I should open up the spindle holes myself, he recommended his friend/colleague Jerry Woods. I am pretty sure the two of them conferred by telephone.
Hopefully not too many people are mis- or underinformed on this topic.