Bolt missing… I Think hmmmm

[HooliganActual]

Chock it up as a learning experience when nobody gets hurt. Reminds me I need to order a new torque wrench. Mine broke on the last tire rotation I did and I'm about to instal the rock krawler triangulated rear 4 link on my mojave. Even if someone else does your installs, every wheeler should have a torque wrench and nut/ bolt check EVERYTHING before and after any big wheeling trips. I've had stuff come loose after a week of wheeling that I know I torque to spec myself.

FWIW (and you may know this but others may not), if you know you torqued something and then a few days later it is loose, wheeling trip or not, it is time to replace that fastener.

What you have described is a fastener that has exited the elastic deformation zone and moved in the plastic deformation zone of the Stress-Strain curve. Next stop is the bolt will reach it's tensile point and will snap.

Not trying to be a know-it-all but I used to teach this in Reliability courses:

Once a bolt has exceeded it's Proof Load, which is likely around "the torque spec", it starts to act like the tab on the top of an aluminum can that has been cycled too many times but hasn't broken free yet.

If you truly torqued the bolt to proper spec and a few days later it is loose again (even though you were wheeling), that most likely means that the proof load has been exceeded, the bolt stretched (which is what actually creates the clamping force you are looking for) and the bolt did not return back to its original shape.

Works just like a rubber band does to hold things together. But an old aged dried out rubber band won't hold its shape and will crack and ultimately break.

Ugh...sorry for the diatribe...I used to teach this stuff every day to mechanics and technicians and since I retired, I have no outlet...LOL

Cheers

Sponsored

 

[Zachanadandy]

FWIW (and you may know this but others may not), if you know you torqued something and then a few days later it is loose, wheeling trip or not, it is time to replace that fastener.

What you have described is a fastener that has exited the elastic deformation zone and moved in the plastic deformation zone of the Stress-Strain curve. Next stop is the bolt will reach it's tensile point and will snap.

Not trying to be a know-it-all but I used to teach this in Reliability courses:

Once a bolt has exceeded it's Proof Load, which is likely around "the torque spec", it starts to act like the tab on the top of an aluminum can that has been cycled too many times but hasn't broken free yet.

If you truly torqued the bolt to proper spec and a few days later it is loose again (even though you were wheeling), that most likely means that the proof load has been exceeded, the bolt stretched (which is what actually creates the clamping force you are looking for) and the bolt did not return back to its original shape.

Works just like a rubber band does to hold things together. But an old aged dried out rubber band won't hold its shape and will crack and ultimately break.

Ugh...sorry for the diatribe...I used to teach this stuff every day to mechanics and technicians and since I retired, I have no outlet...LOL

Cheers

I've never had one loosen in days, a week or more in moab or on the Rubicon, etc and it's happened once or twice. Usually under those conditions it's also wallowed out the mount so it's either drill everything out for larger hardware, weld washers plus new hardware, etc. Even with the stock track bar I upgrade to 9/16" grade 8 as it fits the bushings and mounts tighter.

 

[Zachanadandy]

One thing to be aware of with “replacement” bolts (or original bolts for that matter) is the length of the shoulder of the bolt.

Too many times, and not just in Jeep applications, I see scenarios like this where a long bolt goes through a bushing or something similar and a bolt gets used where the shoulder is not as long as the part through which it passes. By that, I mean that the shoulder ends and the threads begin inside of that bushing insert. The bolt is not as thick and therefore not as strong where the threads are and the threads themselves become stress risers, which can all lead to a bolt snapping where the shoulder to thread transition is inside of the bushing.

Make sure the bolt you use long term has an appropriate shoulder length…

I believe the factory track bar bolts are fully threaded. Finding the perfect length shoulder might be impossible, but a fully threaded 9/16" would still be stronger than the M14, in a 3" grade 8 9/16" bolt you do have some of the threads into the mount but it's still a huge upgrade over stock.

 

[HooliganActual]

I believe the factory track bar bolts are fully threaded. Finding the perfect length shoulder might be impossible, but a fully threaded 9/16" would still be stronger than the M14, in a 3" grade 8 9/16" bolt you do have some of the threads into the mount but it's still a huge upgrade over stock.

Roger that. Mind you, what I’m espousing is an engineering perspective of how things should be…but then the real world intervenes. Everything winds up being a compromise but these are the things to keep in mind, right?!?

In other words, in this application we should try to use the right bolt but it may not be easily obtained. So then we start making the necessary compromises, but then keep that in mind if you find yourself in, say a death wobble scenario, remember to inspect that bolt as it may be the culprit.

Mind you, I’m not trying to be “preachy”. These are just the concepts I would teach Industrial Technicians in order to improve machine reliability and help with their troubleshooting.

Cheers

 

[Lunentucker]

• SKU:6512061AA
• Other Names:06512061aa, Bolt
• Description:
  M14x1.50x74.15. Frt track bar to axle. Rr track bar to axle.

 

[Stan H]

Lost a track bar bolt.

And the dealer doesn’t have any in stock.

Good news is I’m in town and was two blocks from the dealer.

I’ll see if I can source parts when I get home.

What a pita.

Also need the Nut with the holder clip on it .

Sponsored