Cheapest SOA kit anyone??

[cartman98837]

just kinda wondering what was the cheapest way to go about a SOA (spring over axle) kit for a '93 yj

[badger]

Don't expect it to be cheap .This is one mod that shouldn't be done on the cheap.Some people will say just use the stock springs and flip the axles.Problem with that is the springs were not designed to go over the axle and will quickly sag.On top of that they will have really bad axle wrap both front and back.

Next is to address the steering which is really fun.You can either do a drop pitman arm and keep the steering below the springs or get serious and move the steering up above the springs to help protect it.
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One Built XJ

[hutchman]

I am not trying to be a smart ass, just want to understand the physics of why a spring would sag more with the weight pushing against it rather than hanging from it. I have heard this stated on internet before, but just can't understand why it would change the rate of sag of the spring.

[badger]

I would have to say it is the way in which torque is transferred to the spring.When it is in the spring over position you allow more leverage to be placed on the spring which in turn causes it to sag faster.Why do you think after going spring over you have to have a anti-wrap or torque bar on the rear axle and even some times the front axle ?
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One Built XJ

[hutchman]

I know the axle wrap is a fact and I have some trouble understanding that also. It's not a case of calling BS, but more I just can't seem to understand the physics.......

I never considered the difference in torque applied when thinking of the spring sagging sooner. It probably does fatigue the spring quicker, resulting in sag.

But, I guess my problem in understanding is:

If you have an axle on top of the spring in the stock location, the force applied to the spring is counter clockwise when looking at the axle. Moving the axle under the spring only changes the location of the axle and not the direction of the force. It is still the same direction with the difference being that instead of pulling up on the top of the spring, in front of the axle, and pushing down, behind the axle, on the spring, the pull becomes a push and the rear push becomes a pull.

It must be that this change in direction of the force applied to the spring is what causes the axle wrap. The spring must be designed with force applied from the top and changing it to the bottom results in the torque being applied differently from design and increased wear. I think my head hurts.

I hope you see my point. The total force does not change, but is only applied to the spring at a different point on the spring. This must be what causes the axle to wind up and then results in increased sag as the spring fatigues quicker.

Somebody please tell me not to worry about this..........just believe it...

[badger]

Oh I see your point and you hit the nail on the head for the most part.Most leafs are designed to be one or the other and not both.Lets take an Xj rear leaf(sprung over from the factory) for an example.It has a short front half and a long back half.So if it were to be measured from the center pin to each spring eye the rear of the spring would be longer then the front.This in turn acts as a torque arm of sorts.The spring being shorter toward the front reduces the amount of axle wrap because the shorter length takes more torque or leverage to bend.Some people will flip their springs to move the axle back and get a slightly longer wheel base.In doing so they create axle wrap with the same spring they were using before that did not exhibit the problem before flipping them.After doing this most find they have to install a torque arm.They will also find that the spring will fail sooner do to the added stress on the long side of the spring.

Thus me mentioning in the last post about torque and how it effect the spring.I don't know if a YJ spring is equal on both sides of the center pin or not but I would have to guess that its the opposite of an Xj spring and is shorter toward the rear to act the same way.

Now the other thing I was talking about was leverage.Since you now moved the axles center point further away from the spring you have given the axle more leverage to bend or wrap the spring.This is why blocks are considered a bad form of lifting a vehicle and why they also cause a spring to sag sooner.Think of putting a breaker bar on a wrench to break a nut or bolt loose.The added length of the bar in turn gives you more leverage to break the bolt/nut free.

:edit for mistake:
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One Built XJ

[Orangeamc13]

[Orangeamc13]

I'm wondering why sprung under springs from MJs, blazers, durangos,etc., when used over the axle on XJ's, don't exhibit these problems. While the stock sprung over springs on the XJ's frequently have these problems. I would have to believe that it's the beef of the spring that dictates whether it'll wrap or not. At least on moderately powered rigs.
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[badger]

Ya I made a mistake there ,meant to put sprung under .As for axle wrap with other springs from other vehicles.It could be because of several things.Could be the thickness of the main spring ,how many leafs are in the pack,whether the spring has a long or short front half,etc,etc.
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One Built XJ

[Orangeamc13]

[hutchman]

I had not thought of the center pin location. That should make a big difference in how the spring handles torque........

I like to at least try and figure this stuff out from a technical standpoint, but crap sometimes it like trying to pack 10 lbs of mud in a 5 lb bucket........it just doesn't want to fit!