The Stovebolt Site Forums The Shop Area The HiPo Shop Mustang II Lower Ball Joint Failure

Anyone experience lower ball joint failure on Mustang II tubular control arms from Heidts or TCI? There is a safety notice in the November issue of Street Scene magazine discussing this.

I did a little checking, seems the problem stems from using airbag suspension with them, and "laying frame" while driving. it puts the balljoints at an angle they were not intended to run at, causing premature failure.

I've done some checking and some aftermarket companies are using upper ball joints in the lower control arms. This is a misuse of parts according to the NSRA Safety Division. When I contacted Heidts,(I have their control arms in my '51 Chevy Bel Aire) they wouldn't tell me why they are using upper ball joints in the lower arms. They said they have been doing that for years. That still doesn't assure me that it is a safe application.

Interesting. Guess that just confirms why I don't like the idea of using a compact car suspension in a vehicle that weight almost twice as much as what it was designed to handle.

Hi chuckthetruck, Thanks for the webrodder link. It was all very interesting reading. But it did not address the issue that the after market Mustang II type manufacturers are using '76-'80 Volare UPPER ball joints in the LOWER control arms. Any advice on the safety of this application?

your truck prob rejected the ford part!

That is a really good question. Just thinking about the geometry and load directions, one would think they would be engineered differently.
The upper joint carries almost no load vertically, doing most of its work transferring lateral loads to the frame through the control arm.
The lower joint not only transfers lateral loads, but also holds up the vehicle under tension. That nut takes all the vertical loads and transfers them to the spring through the ball joint and the lower control arm.
It is possible that by the time the ball joint is built to handle all the cornering loads, it is strong enough to handle the weight loads as well with a good margin, but I would want an engineer to calculate that before I trusted an upper joint to a lower position.
Just me thinking out loud...

Long before the M-II front suspension was invented, or the guys who use them were even born, chassis fabricators were using Corvair front suspension systems on IFS conversions. They were too flimsy for most of the applications where people attempted to use them. There's nothing new about the "Let's MAKE it fit" attitude. Anyone who bets his life on a too-light or poorly-engineered suspension system isn't only putting himself at risk, but also everybody who happens to be near him on the road when those parts fail. That's the height of irresponsibility!
Jerry

Hi Hotrod Lincoln,
I totally agree with your thoughts.
The question that I can't get an answer to is why are professional aftermarket manufacturers (not back yard mechanics) i.e. Heidts, TCI et al using Volare UPPER ball joints in LOWER control arms. Literally 100's of thousands of these are on the road. Heidts told me that's the way they've been doing it for years.
When I asked if it was a safe application of parts, I got no answer. TCI never responded to my inquiry. I contacted MOOG (they are the supplier for Heidts)and asked if an UPPER ball joint was safe in the LOWER control arm, I got no reply.
Any engineers out there want to share their thoughts and opinions?

Hi Highflyer - You are thinking exactly like me on this issue. Thanks for you thoughts. You are right, I need to consult an engineer.

I'm not an engineer, (flunked out of engineering school by majoring in sports cars and skirts) but my younger brother, who profited from my bad example, managed to make it to graduation, plus getting a Master's in Electrical Engineering and a Doctorate in Plasma Physics. Smart kid! He does computer modeling of auto parts for Ford, Chrysler, and GM as a sideline to his regular job as a research physicist on guidance systems for U.S. Defense Department missiles. I'll ask him what his opinion is on misusing a part by installing it in a position for which it has not been designed nor tested. I've got a pretty good idea what his reply will be.

All parts have a safety factor built in, as there needs to be at least a little fudge factor for overloads. When an assembly is deliberately used on a heavier application than it's designed to handle, it's quite possible that it's already well into the overload range. Just a little extra stress almost guarantees a failure, sometimes a catastrophic one. One of the things I've learned from building round track race cars- - - - -"Build it three times as strong as you think it needs to be, and don't be too surprised if it breaks!" That's particularly true for dirt trackers!
Jerry

How many M-II fronts have been installed and run successfully...sure seems like a popular modification on all kinds of vehicles. Seems light to me, but lots of things have gotten lighter through the years.
A kid who works for me has been going through upper ball joints on his later-model 4X4 because he's got the torsion bars cranked for lift. He's willing to change them frequently so he can keep that look.
Upper, lower, Mustang, Volare...I wonder if there isn't something else to examine for a solution.;\

cm

Thanks for all the info you guys have contributed.
The main concern is with Ball Joint Application. Frank Salerno, Director of Safety Inspections (now retired) of the National Street Rod Association sent out a memo Sept. '10 to all NSRA Safety inspectors informing them of this misuse of parts. It just so happens that it involved the aftermarket Mustang II control arms.
The concern is with the Ball Joint application and not with the control arms or the Mustang II IFS. He had seen Volare UPPER Ball Joints installed in LOWER controls arms fail because LOWER ball joints are heavier and have preload built into them that the UPPERS don't have.
Any more engineers out there have ideas. Thanks