Shackle to leaf ratio

[Windex]

Hey guys got a interesting one here. I currently run a 4.5 inch leaf pack in the rear of my XJ(it has sagged to about 3.0-3.5) so I want to bring it back up to 4.5 to match the front. I have a set of Rough country shackles that have been sitting in my parts bin for a few years now and I could also make up some spacers out of some scrap for the springs.

Now the interesting bit, I have been doing some reading about how due to the fact that the 4.5 springs will are taller they will also be longer than the stock ones. This means that the ratio of shackle length to spring length is quite different to stock. My stock shackle is pretty much perpendicular to the ground, not angled back as they are supposed to be. Adding a longer shackle would give a small amount of lift, change the pinion angle and alter the shackle angle(in a positive direction). I know there are some reservations about shackle lifts on XJ's due to their weak frame mounts but I believe there there must be a number of people on here that are running combination lifts(shackle and springs). I will add to this post as I do a bit more digging.



Read the whole thread as his diagrams are incorrect but they help illustrate the issues with bad shackle angles.
http://www.pirate4x4.com/forum/showthread.php?t=984228

[darksidecustoms]

Have you looked at relocation brackets?
http://www.roughcountry.com/jeep_xtras_1117.html

[junglejuice]

Putting longer shackles in isn't going to change the angle in a significant way but it will get slightly worse as the rear spring eye moves in an arc, the longer the shackle the more it will move towards the front of the car....

The shackle angle currently should be at a better angle now that the spring has sagged then it was when those springs were first fitted though....

[Windex]

Originally Posted by junglejuice

Putting longer shackles in isn't going to change the angle in a significant way but it will get slightly worse as the rear spring eye moves in an arc, the longer the shackle the more it will move towards the front of the car....

The shackle angle currently should be at a better angle now that the spring has sagged then it was when those springs were first fitted though....

You are very right there JJ, more thinking about it and it makes total sense. I think I will go with some small blocks to get a little height back, and look at the relocation brackets.

[Windex]

Just to close the loop on this for future searches, I ended up going with some slightly longer shackles(1 inch higher) and relocation brackets which has made the rear ride much better.

[anthonygubbin]

I don't get it, my shackles are JKS and the angle of the shackle is fine. I can't see how when the spring compress' the shackle angles forward more because mine don't, quite the opposite in fact.

Regards A