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Shackle Reversal benefits...

Discussion in '40- & 55-Series Tech' started by Sorry Dog, Nov 23, 2003.

  1. Sorry Dog

    Sorry Dog

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    I'm some of you already know this, so pardon my ignorance:

    What are the benefits and tradeoffs of a front shackle reversal?
    (especially with respect to either a SOA job or lift springs)
     
  2. 89GASHOG

    89GASHOG

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    Here's an explanation from http://www.nyjeepin.8k.com/tech/shackle_rev.html

    Hope you can tolerate the references to Heeps. They also have pictures at the website to illustrate their explanations.


      Body & Frame Shackle Reversal: Benefits and Compromises
    CJ owners are always looking for a way to make their rigs handle and ride better. While there are many options available, a shackle reversal is one of the most effective -- if you understand how it works. Whether or not you use a reversal could depend on what type of suspension you have.
    If you compare the interactive diagrams below you can begin to see how a shackle reversal helps smooth the ride. As shown, flat stock springs become SHORTER horizontally in length when you hit a bump, causing the shackle to move toward the back of the Jeep and thus exert the force of the bump in a smoother fashion.
    However, with a suspension lift (like most modified Jeeps), the arch of the spring causes the opposite reaction from the shackle. The arched spring effectively becomes longer when it hits a bump, causing the shackle to move in an unnatural forward motion. The force of the hit is exerted on the Jeep rather than soaked up by it.
    A stock Jeep with flat springs will have a reasonable ride due to the fact that the shackles move to the back when the springs compress.

    Lift springs with a standard shackle setup cause the shackle in the wrong direction, upsetting the natural flow of the suspension.
    With a shackle reversal, arched springs direct the force of the impact toward the rear.The same theory behind the smoother ride also translates into better handling on rough surfaces, because 1) the ride is smoother and 2) the force of the bumps is exerted behind the axle.
    Of course, there are some potential disadvantages. For one thing, nosedive is increased during braking in a shackle-reversed lifted CJ. This is caused by essentially the same reasons why the ride is smoother -- the suspension is soaking up the force rather than fighting it.
    In addition, it is imperitive that you install a longer-travel front driveshaft. Not only is there better articulation with a shackle reversal, but the whole axle actually moves toward the rear when the spring is compressed. The combination of those two factors means that the driveshaft needs addition range, and you may have to have a custom shaft built to your specs. Longer-travel driveshafts may not last quite as long either, but you don't want your shaft to become apart when your axle droops (or punch through your transfer case when the axle rises).
    All in all, a shackle reversal may be a worthwhile project if you have a lifted Jeep. Military versions of the CJ-5 were built with the shackle to the rear, and many off-roaders have used this system as the basis behind a smoother, better-handling CJ.
        
     
     
  3. Sorry Dog

    Sorry Dog

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    thanks for the link

    The reason I'm asking is I'm trying to do my "homework" on doing a SOA on a '89 FJ62. I've seen shackle reversal's mentioned a couple of times by people who have done the SO. I'd like to retain as much of the street handling as possible.
    I have pretty flat springs so maybe I oughta leave that part alone.