I know there are tons of threads on death wobble, but the idea popped to mind when I was writing in the "when to use anti-seize" thread, and I figured rather than it getting lost in that thread that has nothing to do with death wobble, or lost in another thread on death wobble that everyone has to read through 100s of pages to find, I figured I'd start a new thread.

Let me start by saying that I have never experienced death wobble on my JK, so I have no way to test this theory out. But, as I was writing about torque and how bolts work on the aforementioned thread, I got to thinking, perhaps this is a possible cause. People are looking at ball joints and lots of other things as the cause and people re-torquing everything, but no one can seem to come up with a viable solution, and I have not seen any mention of the bolts being the culprit.

Anyway, it all has to do with the elastic range and plastic deformation of the bolts and the suspension components. (Thanks MB for correcting me on the terms). Basically, what it comes down to is that most people re-use the original bolts when they replace their suspension, and they could have been stretched beyond their elastic range. At this point, no matter how often you torque them, or how tight you torque them, they will not hold.

Another possibility, also having to do with plastic deformation is that the material of the center bushings on the new suspension is not the same as the OEM parts, which could cause these parts to exceed their compressive strength and therefore deform to the point where they can no longer be tightened.

The problem with this theory, is that it is damn near impossible for us or the dealership or your local mechanic to determine if the bolts or center bushings have become deformed to the point where they will no longer perform properly.

I know I used all new bolts when I lifted my JK and am confident that the engineering and components that come from Clayton are up to par, and I have not
had even the slightest hint of death wobble.

If someone that has it would be willing to invest the time and money into verifying this theory, I would be interested to know the results.

Anyway, if nothing else, its food for thought on what might be the cause of death wobble.

 

I can't figure out how to link a thread, so here is a copy paste of the relevant parts from the "when to use anti-seize" thread:

From me:

Interesting topic. As I learned it, MB is right. The torque is based on the preload for a given size and pitch of bolt, but I think he may have explained it not quite correctly. If I recall correctly, the torque, or preload value, is the limit, or breaking point, for whatever is lesser the value of 1. the bolt's tensile strength, 2. the strength of whatever you are screwing it into, or 3, the compressive strength of whatever is between the bolt and the surface you are screwing it into. I hope that makes sense and is correct. It has been a while since I had to learn this stuff, someone please correct me if I am wrong.

Now, when a bolt gets screwed it, the elasticity of the steel combined with the cylindrical wedge, basically make a spring, and it is the force of the spring exerting pressure on the surrounding material that holds it in place, and this is also where the friction comes from. Theoretically, if you torque the bolt to spec, then it will never come loose. If it is under torqued, then it will come loose because it has not effectively become a spring, thats why there is loctite. If it is over torqued, the bolt is in the elastic region, which means it has gotten to a point where it will not return to its original state. Kind of like when you are playing with the spring in a pen and pull it too far apart and it won't compress anymore. Thats why people will use new bolts especially on engine parts, because you can't really tell if a bolt has been elasticized. So, adding more torque to the bolt is a bad thing as you have deformed the bolt, or worse yet, the surrounding material.

How does anti-seize play into all this? Well, it reduces the friction to reduce binding and prevents cold welding and corrosion. That much I know. However, I don't really know how it plays into the effectiveness of the bolt's holding capability. It has no effect on the stretch of the bolt, other than it makes it easier to over torque it because it acts as a lubricant. The way I learned to do it was to put bolts in the way the factory did it: use antiseize when they do, loctite when they do, and nothing when they do. Now, if you are planning on routinely switching parts, like we often do on our suspensions, go ahead and use anti seize, and torque to spec. But, as a trade off of the eventual ease of removal, plan on spending some time validating the torque on these bolts somewhat regularly (re-torquing).

What I do is the following. Always use new bolts, tighten to torque - never overtighten, and make a decision if I am planning on having to remove the bolt sometime in the near future. If yes, then I will apply anti-seize and resign myself to checking them at every oil change. And if it is someone else's vehicle, I never put antiseize on a bolt that didn't have it originally unless they tell me to.

As to the death wobble issue. I never really thought about this before, but what just came to mind is that it may indeed have to do with the torque on the bolts, but not so much with the bolts but with the material that the track bars and such are made of. If you remember what I wrote earlier about the torque value being based on 3 things, it could be that the material the aftermarket bar is made of has a different compressive strength than the OEM part, causing the torque required to hold the bolt in place to change because the bolt or the compressed materials are being damaged.

Okay, I'm done for now. Someone correct me if I am wrong, it has been a while.

From MB-08-JK(R):

Yeah, the right answer is in there somewhere between what Red and I said. Red's description is more thurough except for the two conditions he was looking for are elastic range and plastic deformation. As long as the bolts stay within the elastic range they remain "springy" but once they are stretched to plastic deformation (beyond the elastic range) they stop being "springy" and they do not return. Please see his beatiful pen spring analogy! In fact they may continue to stretch (creep) and eventually fail. I had not considered inferior center bushings on aftermarket track bars as a potential point of failure. Red is right, if they plastically deform below 125 lbft of torque they will continue to creep and you will always have death wobble. No matter how often you re-torque the bolt. Regarding Red's advice on anti seize; follow it, it's right on.

 

So kinda like when you rebuild a motor, use new head bolts since the old ones have probably stretched from the heat and pressure?

 

And that may also explain why some cases get fixed when replacing the trackbar or certain front end parts. Some kits contain new bolts and some don't.

 

I think you may be on to something here.

 

well I don't think that would be enough to cause DW. Additionally that theory is mooted by the fact that MANY JKers have DW with stock suspensions.... not that your points are invalid in any way

 

I will be willing to try this out after I have re-set my front lower control arms to 23".

I do know that when I was torquing my rear trackbar to 150 ft-ls it seemed like with would never get there and I was thinking about this same thing but if finally torqued.

Once I get the arms back on tonight or tomorrow (weather permitting) I will try out new hardware for the trackbars.

Thanks.

 

What opinions do you have about using some type of lock washer on the bolts of the trackbar? I have not done this but I was thinking this might eliminate the bolts for loosening.

 

I'd buy that in a minute...but then how do you explain death wobble on a completelt stock unaltered Jeep?

 

I feel that death wobble is caused by many things for many people. After you have eliminated the obvious then you might have to crawl around in the mud for any hint at the end of the rainbow and plastic deformation or stain fatigue could be it.

Like I said above, I will be willing to try this very soon.