Shackle Question??

[60thAnivrsryXJ]

A longer shackle does not move the mount farther back. It only moves it down lower. If the mount were moved farther back that would mean the spring is longer than before. The only thing that would do that would be if the spring was compressed more by adding more weight to the rear (the little added weight of the longer shackle would be insignificant). When a leaf spring is compressed it gets longer, when it's decompressed it gets shorter. That is the point of a shackle to allow the leaf spring to change lengths.

 

[Tim_MN]

Look at zfingers pic, the stock leaf is already flattened and is headed for inverted. I had extended shackles on my 3 year old 30,000 mile stock leafs and they went flat after just one summer of offroading. The stock leaf spring tend to go flat under normal use. Extended shackles just speeds this up. I see sagging stock XJ's all the time. You MUST extend the rear bumpstop to prevent the springs from overflexing which is the real reason leaf springs loose their arch. The RE full AAL doesn't change the ride quality too much on my new stock leafs. $75 (RE AAL) + 30 for spacers = about the same cost as extended shackle lift kits. You can always add extened shackles later, IF you need them. Most lifts are already higher in the rear (especially RE) than the front. Look into using extra stock leaves for lift and nearly stock ride. Homebrewed added stock leaf Budget Boost =
http://www.rocklizardfabrications.com/home_brew_budget_boost.htm
.

 

[balloo93]

A longer shackle does not move the mount farther back. It only moves it down lower. If the mount were moved farther back that would mean the spring is longer than before. The only thing that would do that would be if the spring was compressed more by adding more weight to the rear (the little added weight of the longer shackle would be insignificant). When a leaf spring is compressed it gets longer, when it's decompressed it gets shorter. That is the point of a shackle to allow the leaf spring to change lengths.

No, the mount DOES move back. That's why a 3" longer shakle only yields about 1.5" of lift. The rearward movement takes some hieght out of it.

 

[x550x]

No, the mount DOES move back. That's why a 3" longer shakle only yields about 1.5" of lift. The rearward movement takes some hieght out of it.

I think it only gets 1.5" of the 3" because you are only lifting the back of the leaf pack. Therefore you split the difference because the axle is in the middle. If you use a 10" shackle, you will get about 5" of lift.

 

[60thAnivrsryXJ]

Yes you only get as much lift as half the extended length of the shackle because it only lifts the back half of the spring. The mount of the spring to the shackle does not move backwards or forwards though, just down. I thought of another reason this morning to further reinforce my point. Like I said before if the mount was moved back the spring is longer. That is more compressed. If that were the case then as far as the spring is concerned it would be lifting the vehicle less than if the spring were shorter (less compressed). What would be the point of putting on lift shackles if they canceled out the lift of the springs.