Shackle Question I Was Asked...

[007]

I was asked by a non-Jeeper why we don't just run grade 8 all-threads straight through our front shackles at the bottom so as to draw them together (straight, perpendicular to ground), thus minimizing stress on the shackle mounts...

 

[Peanut Butter]

I'm not sure I understand the all thread part. With the right size bolts as long as you don't bottom out the nut there would be no difference. You also wouldn't have any extra threads sticking out.

 

[Posi]

The weakest part of a bolt is the threads this is why you should use a shank bolt apposed to a full threaded bolt. I torque the nuts to 20 ft lbs as well.

 

[Kane]

I think he means as in one threaded rod running all the way from one shackle to another and then use the thread to force the shackles parallel to each other. that's funny.

 

[PaRenegade]

^^ That's the way I'm thinking he meant too. That'd be like hobblin' a horse. As long as it's either parked, driving on flat ground, and only makes slow, wide turns, it would work fine!!

Not sure if he was joking or you were looking for an answer. Tying the two sides together would be limiting the flex of both sides. If one wheel were to go lower than the other, it's shackle wants to move rearward as the spring droops. The other sides shackle wants to go forward as it's spring compresses. This would force both shackles to want to twist towards each other, bending the mount that you were trying to keep straight to begin with. Yes, bad idea.

 

[Torxhead]

I am having a hard time with this also, The oem front spring shackle mounts are a weak point with that rivet clearance hole in them. I have seen a lot of them break on the trail with aftermarket springs. I agree with what Pa stated about limiting spring flex. That would really put stress on those spring shackle mounts.

 

[007]

No you guys have it right and that's what I thought actually. Heading straight and flat would be fine but much more than that you'd create stress where you aimed to prevent it.


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[Hedgehog]

Even flat springs need to articulate on their own. It is a very odd question. Was the guy trying to deal with a specific problem he was having when he asked the question?

 

[Lumpy Grits]

Your 'friend' has no clue how a suspension works.
LG

 

[007]

Your 'friend' has no clue how a suspension works.
LG

Now now LG, it wasn't me. My shackles are at 7 o'clock and 5 o'clock respectively.

I have 1.5" of shackle lift in front and as a result have some. / \ going on that I was griping about on the phone so that's how it came about. Just a harmless question he had and I said it would ultimately limit articulation.

 

[Woolyworm]

Wow, I was just working through this in my head about two days ago. Not on the bottom bolt for all of the obvious reasons stated above, but what about the top bolt? I was considering adding some gussets to my mounts and started thinking about where the stress is. I would think it's mostly side to side from the twisting the spring does as it is compressed. A grade 8 rod through the top shackle bolt holes with nuts added or some other way to limit pinching of the spring, might "share" the strength of the two mounts. A bolt through the top would not limit the independent flexing if the springs. Hmmm.


Wooly

 

[Woolyworm]

Then I thought, as the springs try to force the frame rails open at the bottom or to rip off the mounts, the rod would want to bend down in the middle, so it would need to run through a sleeve of some sort that would tie it to the bumper. Hmmmmmm.


Wooly

 

[Woolyworm]

Then I thought, maybe I should just add some gussets. Funny that the topic came up a couple days after I was thinking about it though. Weird.


Wooly

 

[Hedgehog]

Guys, generally speaking shackle mounts aren't prone to failure, so what are we really worried about here?

 

[Woolyworm]

HH that's kind of where I was at. I've just finished a bunch of other projects and wasn't stoked about tearing all that apart to beef up something that hasn't shown any issues since I've owned it. If they break, I'll fix them. On the other hand, maybe the rod in the bottom would act like anti roll


Wooly

 

[PaRenegade]

Guys, generally speaking shackle mounts aren't prone to failure, so what are we really worried about here?

Well I tend to disagree. You can point to a couple factory weak points on Jeeps over the years and for the later years I would say shackle mounts, mainly the fronts, are on the short list. Even with the short factory length shackles (3") there have been failures due to the poor design of simply a curled strap of steel with a large hole near their mounting point (where the stress is concentrated). But to exacerbate the problem, a lot of folks add longer shackles. That helps to add to the bad rap that longer shackles usually get and why I always make it a point, when defending longer shackles, that the mounts need to be beefed up as well. Longer shackles add leverage force to the mounts. Think of a short screwdriver as a pry bar, vs. a long screwdriver. Hence the tongue in cheek comment 007 made about his shackles being clocked at 5 & 7 o'clock. It's a common occurrence for the factory mounts to twist slightly.
In my book, any suspension upgrade should include an aftermarket shackle mount for at least the front (it has the added stress of turning, with the weight of the engine). It's not expensive either.

 

[Lumpy Grits]

Guys, generally speaking shackle mounts aren't prone to failure, so what are we really worried about here?

Can't agree with that at all. I have lost count of how many front CJ shackle mounts I have had to rebuild and then weld to the frame. Yes-These are heavy use Jeeps run'n 33"+ tires.
The biggest deal is the rivet clearance hole in the front shackle, that allows the shackle 'eye' to flex and then crack.
LG

 

[PaRenegade]

Hedgehog - I came across two pictures of how these mounts tend to fail. The first one is how they crack and eventually come apart on either side of the rivet relief hole. The other shows how they can twist from too much side load from say an off camber hillside trail.

 

[Lumpy Grits]

Yuppers-That's what they do.
That's why I welded my rebuilt ones to the frame.
LG

 

[007]

Yeah heck with this. I'm replacing mine.


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