I too have talked to iro today. Here's my plan for the minute...
They sell a 12mm upgrade, (12mm=.476"), with a flex joint to replace the stock bushing. Cost was $40ish, but I bought a tool to insert the bushing for another $25. I probably did t need the tool, but $25 to make my life simple is cheap.
They don't have issues with their arms, and they don't believe there has ever been a bolt break.
Questions for Craig that he can't answer:
1). Is the bolt that was in the upper the hardened metric bolt originally supplied with the kit?
2). Could the bolt have been loose and worked it's way out?
Me playing devil's advocate:
Without having the broken bolt to prove it broke, it's feasible to think it may have just come out. I would think the possibility of having a piece of the broken bolt (if it broke) still within the arm or bushing would be good.
I don't know. Just throwing theories out.
The flaw in the design is that no matter how tight you make that bolt, it's over a slot that's close to the edge of a piece of what, 1/8" flat stock? Which is over a slot in a piece of 3/16 or 1/4 stock, with the slots crossed?
It's going to take a substantial amount of bolt preload tension (far more than it would through a regular hole) and a very substantial bushing inner sleeve wall thickness to make me comfortable with that setup. In fact, by the time you put enough preload on it, you're risking coning the washer or head of the bolt and spreading the slot in the caster adjuster apart instead. Vibration and suspension force will only exacerbate this problem.
Basically what I'm saying is that I'm really not comfortable with a slotted bracket like that being the single point of failure. Especially when it's two stacked up slots going in opposite directions. Doing that, you're gonna cut the surface area that's being preloaded effectively by a HUGE amount - I'd say something like 50% (when you've already eliminated half your upper control arms) SWAG, I can run the numbers if you want. And that's not even taking into account the fact that the part is powdercoated (and thus must be retorqued after the powdercoat works its way out of the joint... because it will) and the issue with the preload trying to spread the two sides of the slot apart.
The factory got away with this kind of setup on the LCAs on the TJ and ZJ because they used a large flange headed bolt, thick inner bushing sleeves (more contact area), and made sure the slot was far from the edge of the metal stock it was in, which helps prevent the sides of the slot from spreading apart. And they only did one slot, rather than two crossing slots in two different pieces of metal, which makes it a lot easier to handle.
If they used any other setup I would be perfectly happy with it. It's just plain not a sound design mechanically. By the time the design is changed enough to make it sound, it's easier to just use a link, some tabs, and a pair of heims or bushings like... every other stock-axle capable radius arm setup available that allows caster adjustment.
So yeah, I'd bet that the failure mode was this:
* Bolt preload went down after install due to paint/powdercoat on (very minimal) contact areas between upper leg of control arm and inner bushing sleeve ends
* Bolt sheared, or the nut simply vibrated loose once preload was below spec.
* axle goes walkabout
It may seem like I am harping on this needlessly but this is literally the third time I have seen this suspension kit fail in exactly the same way after it was installed by someone I would trust to work on my rig any day without me watching. And it will not be the last.
Another of the NAC guys:
http://www.naxja.org/forum/showthread.php?t=1055578
Altrocker's
And either Shawn Connors or Colin Channell (I forget which, always get those two confused) had exactly the same thing happen offroad a few years ago, ruined all the same parts, had to get dragged out and flatbed ride home.
If this is not heeded it is only a matter of time until someone loses their life. I am really, really glad that didn't happen to Craig, like he said, a few minutes before he was doing 60.
