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Unread 06-11-2012, 01:08 PM   #1
VACJ5
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Tech topic: Boomerang Shackles

I see every few days a thread that will pop up asking questions about boomerang shackles. Some ask the same questions and some ask different questions. I figure I would take a few minutes and throw a good amount of info together about shackles. *please note that all the pictures I am using are just ones I borrowed from a quick google search.

Some quick shackle facts:

-Stock YJ shackles are 4" in length center of bolt to center of bolt, stamped sheet steel.

-For every 1" over stock length, you are effectively adding 1/2" of lift to your rig.

-Extending your shackle length will directly effect your pinion angle (not by much, but it will still change you pinion angle) and your caster angle (which effects your steering)

-As a benefit though, it allows for more suspension articulation (but there is a fine line between having a bunch of wheel travel and a rig that doesnt handle well on the road)

-Extended shackles also effect your approach/departure angle. (Too long of a shackle, and you are running the end of your leafs into rocks or obstacles)


Boomerang shackles:

-Help with shackle inversion. (Where the suspension drops and the shackle lays flat against the frame rail, commonly resulting in a bent leaf spring... see pics). The center tube in the shackle comes in contact with the frame to keep the shackle from inverting. It also stabilizes the shackle in a left/right direction when turning the steering wheel (with out a reinforcement, you will experience a bit of body roll or the wheel not wanting to return back to center).





Inverted shackles caused this:



-Mounting direction. Traditionally people mount them with the "V's" pointing toward the center of the rig. Some boomerangs have a long side and a short side. I won't say that 1 direction is better than the other because all jeep suspensions are different. Your springs may settle differently than another persons. So in my opinion, mount them up, cycle the suspenion and see what works best in terms of clearance. (Below you can see one mounted short side up & the other long side up).

Short side up:



Long side up:



-The "V" in the shackle design also helps with clearancing bumpers and crossmembers allowing the suspension to cycle further.



-Torque spec for shackles. This has been a moving target... seems like the number is always decreasing. 1 fact remains true. If you hog down and over tighten your shackle bolts. Your leaf springs will bind causing a rough ride and poor flex. I suggest 45-50 ft-lbs. But to each their own.

-Will you need new shocks? Depends. How much lift do you have over stock? How long of a shackle are you planning on running? If you have stock shocks on a 2.5" lift with another 1" shackle... yes, you are going to need new shocks. If you are going to run a 5/8" shackle, you will most likely be fine.

-If you dont want boomerang shackles but are concerned about shackle inversion, you can always weld essentially a "bump stop" for your shackle to keep it from being able to lay flat against the frame rail

-If your shackle has become inverted. Go find a spot on the trail where you can droop the inverted side, or get a hilift and lift the side with the inverted shackle. You will most likely need a prybarlike device in order to help flip the shackle around. BE VERY CAREFUL, you are dealing with the weight of your rig and the energy from your suspension. Don't go sticking your head or limbs just anywhere when doing this.

I think I have touched base on many of the key things about shackles, extended shackles and boomerang shackles. If anyone sees something I missed, let me know. I'll add it on. Hopefully this helps some people out when they are looking into shackles

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Last edited by VACJ5; 06-11-2012 at 01:12 PM.. Reason: spelling... stupid fat fingers.
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Unread 06-11-2012, 01:20 PM   #2
jeepster93
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Mine:
They are a 5/8 inch lift. The 5/8 inch compensates for the larger tubes on the 8.8.
A small amount of lift will also help in getting the springs off the rear frame.
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Unread 06-11-2012, 02:31 PM   #3
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Unread 06-11-2012, 02:40 PM   #4
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Nice write up. a few people told me that you cant use boomerang shackles in front, i wouldnt see why not. Theres a few companies that only sell them as "rear shackles" and sell the straight ones as front. why is that?
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Unread 06-11-2012, 02:51 PM   #5
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Nice write-up and pics. Here's one that Brandon YJ did a few years ago. Good info as well but no pics. Just thought I'd add the extra info to the thread for a one stop shop.

All about shackles

Quote:
Originally Posted by 04WJny View Post
Nice write up. a few people told me that you cant use boomerang shackles in front, i wouldnt see why not. Theres a few companies that only sell them as "rear shackles" and sell the straight ones as front. why is that?
Not sure why that is. Maybe they are afraid of possible issues with running them in the front. But I see no issues.
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Unread 06-11-2012, 03:33 PM   #6
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Love my Boomerang Shackles! I run them front and rear (stock length) and have no complaints whatsoever. I have had them on for a while, but haven't had much time or opportunity to test their Offroad manners. On road (as opposed to my old beaver teeth shackles) I can actually stand to drive my YJ everyday now haha. Affordable and effective, from VACJ5, would highly recommend to anyone thinking about boomerang shackles!
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Unread 06-11-2012, 03:58 PM   #7
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Quote:
Originally Posted by Anticanman View Post
Hey, that's my picture!!
Yeah, that other thread we were posting in kinda gave me the idea to start this one. Hope you dont mind me using your pic.

Quote:
Originally Posted by 04WJny View Post
Nice write up. a few people told me that you cant use boomerang shackles in front, i wouldnt see why not. Theres a few companies that only sell them as "rear shackles" and sell the straight ones as front. why is that?
A lot of people run them in the front. My rig included.

Quote:
Originally Posted by Louie4 View Post
Nice write-up and pics. Here's one that Brandon YJ did a few years ago. Good info as well but no pics. Just thought I'd add the extra info to the thread for a one stop shop.

All about shackles

Not sure why that is. Maybe they are afraid of possible issues with running them in the front. But I see no issues.
Yeah, that info is from the Quadratec website... I saw that in my search for pictures for this thread. A ton of good info there too!
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Unread 06-11-2012, 04:06 PM   #8
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Unread 10-04-2012, 09:58 PM   #9
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Say I buy two sets of these from bersrk :

http://www.ebay.com/itm/JEEP-YJ-BOOM...df15d9&vxp=mtr

What should I get for the bushings/bolts? This is what I'm hung up on...I have stock shackles on my rig right now. Bushings are shot. I figure I might as well upgrade everything in preparation for different lift springs anyways.
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Unread 10-04-2012, 10:24 PM   #10
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Bolts are going to be grade 8 replacements and the bushings are going to be for your frame from daystar and spring specific.
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Unread 10-04-2012, 11:34 PM   #11
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shackles can be any shape you want, zig zag, whatever and they will act exactly the same provided interference is not a factor. the boom portion was strictly to get around the rear crossmember. even with them, trimming is often needed.

Quote:
Originally Posted by jeepster93 View Post
this is an example of possible waisted oppertunity. all that stuff bolted on combined with the military wrap will cause the shackle movement to stop prematurely. if you draw a line from bolt to bolt i dont think a regular shackle would even fit. the boom appears to allow maybe a half inch travel but definitely less then the design was made to accomplish. if the spring cannot flatten out with the pivot of the shackle it will do so without the shackles help and you will get a jarring stop to uptravel and a bouncy ride.

Quote:
Originally Posted by VACJ5 View Post
(center bar) It also stabilizes the shackle in a left/right direction when turning the steering wheel (with out a reinforcement, you will experience a bit of body roll or the wheel not wanting to return back to center).
if the shackle is built proper and assembled properly there will be no negative effects without the center support. stock units do not have them. it is not uncommon to go without as certain springs wont allow room.


Quote:
Originally Posted by VACJ5 View Post
-Torque spec for shackles. This has been a moving target... seems like the number is always decreasing. 1 fact remains true. If you hog down and over tighten your shackle bolts. Your leaf springs will bind causing a rough ride and poor flex. I suggest 45-50 ft-lbs. But to each their own.
that fact is only true for poorly designed shackle systems. if it is designed right you can hog down on them all you want and they will pivot just fine. once one understands that all rotation is to take place between the metal sleeve and the bushing material, and not the bolt and sleeve, then there is no reason to leave them loose. the sleeve and bolt should in effect act as a single unit. many years ago it was popular to leave them loose and double nut the bolts. this only leads to premature wear on the bolt itself. i have a bolt half way worn through due to this. this is further an issue if you use greasable bolts in your shackles. if the sleeve is allowed to rotate on the bolt then the drilled holes that allow the grease to pass into the bushing will quickly misalign and the system becomes useless. the source of the problem is on most aftermarket systems the sleeve is too short allowing the polyurethane to be squeezed by the plates. combine this with inadequate lubrication and you will have bind. a proper length sleeve and even some delrin washers will make then rotate very smooth even at FSM torque specs.
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Unread 10-05-2012, 02:16 PM   #12
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My shackle bolts are super super tight and my suspension moves fine . My bolts pull the sleeve tight against the shackle and allow room for the bushing to rotate though. I used the stock sleeve with day star bushings
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Unread 10-09-2012, 05:52 AM   #13
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VACJ5, No pics of your work?

As far as torque, the real issue is in the bushings. If the center sleeve is too short any ftlbs will bind the spring and if it is too long no matter what gorilla juice you put to the wrench the springs will move side to side and feel sloppy.

I put in the center post on the booms I bought from VACJ5 and ground them down to match the bushing sleeve length. They work great, no binding at all and no noticable slop in ride or steering.
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Unread 10-09-2012, 07:52 AM   #14
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I run vacj5 booms And they work great.....
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Unread 10-09-2012, 08:26 AM   #15
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Quote:
Originally Posted by fratis View Post
shackles can be any shape you want, zig zag, whatever and they will act exactly the same provided interference is not a factor. the boom portion was strictly to get around the rear crossmember. even with them, trimming is often needed.


this is an example of possible waisted oppertunity. all that stuff bolted on combined with the military wrap will cause the shackle movement to stop prematurely. if you draw a line from bolt to bolt i dont think a regular shackle would even fit. the boom appears to allow maybe a half inch travel but definitely less then the design was made to accomplish. if the spring cannot flatten out with the pivot of the shackle it will do so without the shackles help and you will get a jarring stop to uptravel and a bouncy ride.


if the shackle is built proper and assembled properly there will be no negative effects without the center support. stock units do not have them. it is not uncommon to go without as certain springs wont allow room.




that fact is only true for poorly designed shackle systems. if it is designed right you can hog down on them all you want and they will pivot just fine. once one understands that all rotation is to take place between the metal sleeve and the bushing material, and not the bolt and sleeve, then there is no reason to leave them loose. the sleeve and bolt should in effect act as a single unit. many years ago it was popular to leave them loose and double nut the bolts. this only leads to premature wear on the bolt itself. i have a bolt half way worn through due to this. this is further an issue if you use greasable bolts in your shackles. if the sleeve is allowed to rotate on the bolt then the drilled holes that allow the grease to pass into the bushing will quickly misalign and the system becomes useless. the source of the problem is on most aftermarket systems the sleeve is too short allowing the polyurethane to be squeezed by the plates. combine this with inadequate lubrication and you will have bind. a proper length sleeve and even some delrin washers will make then rotate very smooth even at FSM torque specs.
I am aware of the stuff I have attached to the frame crossmember. The darn thing(crosmember) almost fell off. The bumper/tire carrier is heavy and just about pulled the thing apart. So I got some reinforcements and welded and bolted them to the bumper and frame. This will effect the shackle's movement, I know this. I can hear it bang on the frame, so I know of the issue.
Also thought of cutting the military wrap from the rear springs, it has been suggested to me.

So...
What do you sugest?
I am open...to better ways. I would love more suspension movement.
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