Help...I don't get it

Just the other day, a friend of mine gave me a shackle reversal kit...It was left over from a project that he sold before he finished it...So, I had every intention of putting this on my 73 CJ. I got the shop ready, laid everything out...and then started to think about what I was going to achieve by putting this on...
I can see where this would probably smooth out the ride...due to the wheel moving rearward as you hit a bump....But, the big selling point of these kits seem to be that it will give your Jeep better road manners and stop it from wandering...This is the part that I just don't get...Now, I admit that I am not exactly a wizard when it comes to suspension geometry...but I just do not understand how putting the shackle in the rear would stop wandering as opposed to it being in the front.
The ONLY answer I personally can come up with is that when the front shackle is moved to the rear, it would turn your axle...which would get you more caster.
Now....I can see how this would ABSOLUTLY make a jeep drive better...IF it had too little caster...or negative to begin with....But what if your jeep already has the correct amount of caster (mine) how will this kit help road manners on a front shackle CJ that has been done correctly.
I am sure this is something that is very simple and I am just missing it.

 

Because the front of the spring is fixed to the frame it can not move side to side like shackles do. It helps keep the axle movement under control better. The problem I have is that you may be sacrificing some off-road performance in the interest of better on road manners.

I agree with you in that a properly set and maintained stock system should be almost as good as a reversal.

 

Snake oil IMO.

Changes the geometry of how the spring bushings hold the axle in line with the frame, but if the bushings are in good condition, the strength of the bushings should be enough to keep the axle and frame in line.

Also changes the geometry of the weight transfer when you brake, and increased nose dive has been reported.

The baja racers would reverse the shackles, but that was done only to prevent bending the springs if they hit something at speed.

 

So how about this........Would a detachable anti-sway bar have the same affect?
By the way...I'm just asking out of curiosity...my CJ drives just fine and does not wander.

 

If it ain't broke...

I wouldn't try to fix a problem that may not exist.

 

Here's an analogy.

Picture a ball balanced at the top of a hill. Even the slightest push will make the ball roll down the hill. This is an unstable equilibrium, like the forward facing shackles. The shape of the hill is analogous to the suspension geometry. Gravity wants to pull the ball down the hill, just like the driving forces trying to push the springs out of alignment with the frame. When the ball is at the top of the hill, everything is aligned.

Now add some springs that hold the ball at the top of the hill. These are your spring bushings. As long as the springs are stronger than any push you can give the ball, everything stays in alignment.

The shackle reversal turns the hill into a valley. You still have the same springs and pushes, but now gravity works with the springs to move the ball back into alignment. This is a stable equilibrium.

Of course, there are other factors at work, like the braking weight transfer. The Jeep engineers could have put the shackles at the rear, but they chose not to; in fact, the moved the shackles to the front after the first few years of CJ-5 production.

 

I'm not...I'm Just trying to gain some "why something is done" knowledge.

 

Nice analogy, very understandable.

 

Try this one. Stand at the front of your Jeep and have someone turn the steering wheel back and forth, putting some pressure on the steering system. Watch the shackles. It's more pronounced with longer than stock shackles, but you'll probably notice them moving back and forth at the bottom. This is one of the things that creates the "all over the road" feel of a Jeep. With the shackles at the rear, this doesn't happen. I'd never own another Jeep without a reversal. Just my .02

 

take a ride with me on the 9th at Brown's camp....I have a shackle reversal on mine and you can see what it does. Mine drove perfectly down the road at 70 MPH when I first got it, but tearing thru the bogs has loosened things up a little. still drives OK, just a little loose now. Rides very nice (with SoftRide springs) going in a straight line, but leans too much in the corners.

 

I've always disliked long shackles...It's usually one of the first things I will change (if someone has done it)...But even with a very short, very heavy shackle, with new bushings...I can see them move a little when steering. So when you put them at the rear...all that movement stops? I just had it in my head that they would still move...but would just be moving at the back.
Good to know.

 

Yeah, they'll still move. But the straight-ahead tracking of the wheels will make the springs tend to return to center, rather than the opposite. Lateral forces (turning) will push the springs out of line the same, reversed or not.

I'd expect less wander going down the highway with reversed shackles, but IME the stock setup in good condition with reasonable lift will track just fine anyway. Reversal seems like a solution to something that shouldn't be a problem. IMO of course.

 

Here a question for you...that is kind of related to the topic...Can you have too much positive caster?....I mean...leave aside the drive shaft angle for a second...Would a lot of positive caster do anything negative to handling...Maybe make the steering a little more stiff?

 

Yep, makes the steering hard. You have to lift the front end with the steering to overcome the caster. The return to center could be too fast - let go of the wheel and it spins quickly back to center.