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What leaf springs require boomerang shackles?

maxbraketorque

NAXJA Forum User
Location
PDX
I've been collecting measurements on direct fit leaf springs for the XJ that provide a 3.5" to 4.5" lift, and while a longer-than-stock shackle is needed for a few (4.75" c-to-c is sufficient), so far, I haven't found any that require a boomerang shackle. Are the boomerangs required for higher lift springs or perhaps for adapting non-XJ springs to an XJ?
 
It depends more on the application than the springs themselves.
 
If you are collecting measurements of XJ lift springs, please share. That would be good information to have searchable.

I know (new) stock springs run 49" eye-to-eye and 6.75" of arch.

As far as I know, most aftermarket lift springs are just re-arch factory springs. The increased arch then makes them shorter eye-to-eye. This is why most lift kits result in vertical shackles.

Boomerang shackles, as I understand, are to avoid contact with the rear frame to give a little more travel. But often still end up with a vertical bolt alignment with most aftermarket lift springs.

398011d1503670434-boomerang-shackles-20170825_070051c-r.jpg


The only real way to adjust shackle angle is with shackle relocation boxes that allow you to move the upper hole as necessary.

SRB3_cc4db418-b5cd-4c02-ac2d-80fe35696e6b_1200x1200.jpg
 
Here is what I have so far on leaf springs:

OME CS033RB - 4" lift springs - 52" eye-to-eye flat length as quoted by ARBUSA
OME CS033RA - 3" lift springs - 52" eye-to-eye flat length as quoted by ARBUSA
Rough Country 8047D - 4" lift springs - 52.5" eye-to-eye flat length as measured by me on two pairs
Iron Rock Offroad - 3.5" lift springs - 53" eye-to-eye flat length as quoted by IRO

Based on my measurements, the IRO leaf pack, which is the longest XJ-specific spring that I have found to-date, will clear the rear crossmember when using a straight shackle that is 4.75" eye-to-eye (which is what I currently have). So I have yet to find a leaf pack that needs a boomerang, but I wouldn't be surprised if the Deaver leaf pack needs one. I called Deaver a few days ago, but I didn't ask for the flat length because they told me that the spring rate was north of 200 lbs/in which is more than what I want.
 
I'd like to know what defines a "boomerang shackle", the SFR shackles I just bought are not advertised as boomerang but have the same "offset" but in a different form as Ironman's advertised shackle???
 
It’s just a boomerang if it has that angle to clear the rear bumper crossmember area. I’m using SRB with my own DIY ironman style shackles. Love the adjustability and flex
 
My point is that I can build a "C", "L", "V", or a offset. They all do the same thing and would properly be called "high/extended clearance" shackles!
 
Here is what I have so far on leaf springs:

OME CS033RB - 4" lift springs - 52" eye-to-eye flat length as quoted by ARBUSA
OME CS033RA - 3" lift springs - 52" eye-to-eye flat length as quoted by ARBUSA
Rough Country 8047D - 4" lift springs - 52.5" eye-to-eye flat length as measured by me on two pairs
Iron Rock Offroad - 3.5" lift springs - 53" eye-to-eye flat length as quoted by IRO

Based on my measurements, the IRO leaf pack, which is the longest XJ-specific spring that I have found to-date, will clear the rear crossmember when using a straight shackle that is 4.75" eye-to-eye (which is what I currently have). So I have yet to find a leaf pack that needs a boomerang, but I wouldn't be surprised if the Deaver leaf pack needs one. I called Deaver a few days ago, but I didn't ask for the flat length because they told me that the spring rate was north of 200 lbs/in which is more than what I want.

From IRO website under their 3.5" XJ springs:

"IMPORTANT PRODUCT NOTE: These springs are longer than the OEM springs. Because of their length, they will require the use of either a lift shackle, boomerang style shackle, or shackle drop/relocation kit."
 
Yep, a lift shackle is sufficient, but a boomerang is not needed. I've verified this from my own measurements with my RC springs that are only 0.5" shorter. With the IRO springs, my shackle arms will come within about 1/8" of the rear crossmember when the springs go flat. Shackle angle would be about 30-33 degrees which isn't much if looking for a shackle softening effect on the rear suspension.
 
If you want to sell mass produced shackles to the jeep crowd you tell them its a boomerang shackle.

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Yep, a lift shackle is sufficient, but a boomerang is not needed. I've verified this from my own measurements with my RC springs that are only 0.5" shorter. With the IRO springs, my shackle arms will come within about 1/8" of the rear crossmember when the springs go flat. Shackle angle would be about 30-33 degrees which isn't much if looking for a shackle softening effect on the rear suspension.

Great thread, thanks for getting it going.

I didn't mean you were off-base, just pointing out their comments. Re-reading I see it's either boomerang or SRB for the IRO springs.
The debate with myself is whether to add the SRB I have in hand to improve angle but that will add lift (in lieu of Stinky or such) with shackles like these:

https://www.ironrockoffroad.com/Mer...creen=PROD&Store_Code=IROR&Product_Code=10456
(0-.75")

either with my existing 3.5" OME springs or with the IRO 3.5" leafs.

Also considering whether to go with the additional leaf with IRO for more load capacity since I haul so much gear on the trail.

I'll go back to listen/learn mode. We need a "like" button on these threads..
 
So, I'm about 99% certain that a boomerang is not needed for the IRO 3.5" leaves. Just needs an extended shackle. A 4.75" c-to-c such as the Rusty's I have will not hit the rear crossmember with the IRO. It will come within about 1/8" of the rear crossmember when the leaves go flat.

Your desire for an additional leaf and doing an SRB to change shackle angle to improve ride are somewhat at odds with each other. Laying back the shackle improves ride quality by reducing the effective spring rate at the rear wheels. If you often carry a fair amount of gear and are contemplating an add-a-leaf, then you will likely be happy with the IRO without an SRB and without an add-a-leaf.

The other key benefit of an SRB is that it also adds some rear wheel travel. This is because as the shackle is laid down, it moves through more vertical travel as the spring compresses, and that increases wheel travel compared to a shackle that starts off upright. So you'd be missing that benefit if you didn't do an SRB.

If I were you, I'd start by slapping on the IROs along with a standard extended shackle such as the Rusty's. See how that works, and if its too firm or you want more wheel travel, then its SRB time.

BTW, I've figured out a way to modify the factory shackle box to position the shackle mounting point forward by 2" without sacrificing any structural integrity. In fact, it probably strengthens the factory shackle box a bit. A few fabricated parts are needed, and it requires making two holes in regions that are not accessible with a drill. Would need to be ground holes. But still easier than doing an full-on SRB replacement. Now if I could find someone who wants to make a kit.
 
About 75*. 5.0" center-center. No body interference.
How about SRB for another 1.5" or so with existing OME 3.5" and call it good. Or am I obsessing over angle? Not after lift but considering swap to Metal cloak 4.5" up front with CAD. Round and round I go.
Picture won't post.

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Your shackles are at 75 deg from horizontal now, i.e., 25 deg off vertical? Are the leaves almost flat? Mine are just slightly past vertical right now, maybe sitting at 10 deg off vertical. Is the ride too firm with OME? SRB is less money than new springs, so if you are ok with continuing to use the OME and want a softer ride with a bit more travel, then an SRB may be the hot ticket for you. Also, the rear will sit lower after the SRB unless you go with longer shackles or use an SRB that adds some lift. It looks to me that the shackle mounting holes in the SFR are about 0.5" further down than the stock location, so that SRB would add a bit of lift for no change in shackle angle.
 
And yes, springs are pretty flat.

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Angle with extended shackle.
a2036778922250fea86978a007625f0b.jpg


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