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Lift Shackle Comparison Iron Rock Offroad Vs StinkyFab

Point to point length is all the springs care about, shape is used to provide clearance from obstacles.
 
NOTNSUV said:
Please explain when a boomerang shackle is needed. Is it for springs that are a bit longer than OEM? Is there a time when they should NOT be used (ex: my current OME 3.5")?I'm looking at Deaver 4" springs and they recommend a boomerang shackle. I'm pretty ignorant of the geometry back there. Enjoying this thread, tho'.

Edit: Hey lookie here https://www.quadratec.com/leaf-spring-shackles-explained I'll do some reading.
Click to expand...

The shackle rotates on its pivot point to accommodate the changing length of the spring. If the spring is substantially longer than stock, then the shackle can rotate far enough to hit the back of the shackle box, and when that happens, the spring cannot easily compress further, effectively limiting wheel travel. A straight longer shackle will make this more difficult to happen because a longer shackle travels through less arc as the spring compresses and extends rearward, however some springs are so long that even a reasonable length straight shackle will hit the rear of the shackle box. A boomerang shape shackle can solve this issue.

For a point of reference, the distance between the front leaf spring mount and the shackle mount is 51.0". Supposedly a 52.5" long spring can work with a stock shackle, but just barely. Anything longer than that definitely requires an extended length shackle, and my guess is that anything more than 53.5" would require a really long straight shackle and/or a boomerang shackle.

Not to purposely cloud the situation further, but virtually all boomerang shackles that I've seen are actually pretty long too. The increased length increases the amount of lift at the rear. A rule of thumb is that for every 1" increase in shackle length over stock, the rear will sit 0.5" higher. Its probably closer to 0.4". The shortest boomerang shackle that I've been able to find lifts the rear by 1" (i.e., it is two inches longer than stock). It might even be 1.5" of lift for the shortest available boomerang shackle. Whether you go with a boomerang shackle or straight aftermarket shackle, you need to account for its length when selecting the amount of lift of the spring that you purchase.
 
maxbraketorque said:
The shackle rotates on its pivot point to accommodate the changing length of the spring. If the spring is substantially longer than stock, then the shackle can rotate far enough to hit the back of the shackle box, and when that happens, the spring cannot easily compress further, effectively limiting wheel travel. A straight longer shackle will make this more difficult to happen because a longer shackle travels through less arc as the spring compresses and extends rearward, however some springs are so long that even a reasonable length straight shackle will hit the rear of the shackle box. A boomerang shape shackle can solve this issue.

For a point of reference, the distance between the front leaf spring mount and the shackle mount is 51.0". Supposedly a 52.5" long spring can work with a stock shackle, but just barely. Anything longer than that definitely requires an extended length shackle, and my guess is that anything more than 53.5" would require a really long straight shackle and/or a boomerang shackle.

Not to purposely cloud the situation further, but virtually all boomerang shackles that I've seen are actually pretty long too. The increased length increases the amount of lift at the rear. A rule of thumb is that for every 1" increase in shackle length over stock, the rear will sit 0.5" higher. Its probably closer to 0.4". The shortest boomerang shackle that I've been able to find lifts the rear by 1" (i.e., it is two inches longer than stock). It might even be 1.5" of lift for the shortest available boomerang shackle. Whether you go with a boomerang shackle or straight aftermarket shackle, you need to account for its length when selecting the amount of lift of the spring that you purchase.
Click to expand...

Excellent - and understandable. Thanks.

Now I can go measure the OME springs I've had on there for years and see where I am. An inch more lift would not hurt this thing.
I do carry hella load with JCR tire carrier bumper with 2 rotopax and a high-lift + recovery gear, spare parts, fluids, etc. in the back. I'm going to make the rear seat into a platform to move some of that gear forward, between the wheels.

Also looking at possibly replacing the OME springs with either IRO 8-leaf or Deaver (just now hearing about racing on Deaver - I don't race). Maybe a good boomerang on the OME to see if it improves before shotgunning in new ($$$) springs.
 
NOTNSUV said:
Excellent - and understandable. Thanks.

Now I can go measure the OME springs I've had on there for years and see where I am. An inch more lift would not hurt this thing.
I do carry hella load with JCR tire carrier bumper with 2 rotopax and a high-lift + recovery gear, spare parts, fluids, etc. in the back. I'm going to make the rear seat into a platform to move some of that gear forward, between the wheels.

Also looking at possibly replacing the OME springs with either IRO 8-leaf or Deaver (just now hearing about racing on Deaver - I don't race). Maybe a good boomerang on the OME to see if it improves before shotgunning in new ($$$) springs.
Click to expand...

Nothing is going to replace the lack of spring rate, a longer shackle will only make it worse unless you stand it almost vertical.
 
Ok, difficult to measure the spring without another pair of hands.. will get that done. Looks like 53" on my own but want to be accurate

Meanwhile, I notice register marks where there's contact, on both sides so it seems I do need a bit longer shackle set. I have RE 2700 5" NIB but that's more lift than I want (2.5") so looking at some with less lift and might as well go with the boomerang. Ya think?

"Nothing is going to replace the lack of spring rate, a longer shackle will only make it worse unless you stand it almost vertical."

Recommendations? Looking at IRO with 8th leaf. Right track?

Appreciate all the input.

Or: at .75" lift. https://www.ironrockoffroad.com/product/xj-heavy-duty-adjustable-lift-shackle.html
 
Last edited:
"Please explain when a boomerang shackle is needed" The Deaver leaf spring has a unique rear eyelet configuration. Unlike other leafs where the eyelet rolls up up and is higher than the first leaf, the Deaver leaf pack actually rolls under so the shackle can hit the top leaf and bind and limit travel. SFR made their shackle to allow the shackle to lay down without binding on the top leaf. This really isn't an issue with any other leaf design ( OME, Rubicon Express, BDS, Ironrock etc.)
 
Thank you.

Probably going with RE shackles I have in hand and possibly HD bolt in SRB. Just wondering how much lift this will net. I understand it will depend on final shackle angle. I think I can afford an inch or so without getting the stinkbug look.
 
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