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Long Arm Vs Short Arm for TJ

Up to about 3.5 inches, the long arm offers very little advantage over SA.As you go past 3.5 inches its clearly advantage LA.Or so it would seem, however that is another thread, but for purposes of this discussion LA is holding most of the cards as the lift passes the 3.5 inch mark.

When only the best will do

When speaking of SA Vs LA its the TJ in terms of SA = OEM length and OEM attachment points.  LA=uses the axle attachment points and locates the opposite ends of the arms somewhere past the OEM attachment points.

A way of looking at this:

You max point of articulation is 90 degrees up and 90 degrees down ( in theory) you can go no further than that.  As you lift your rig you are using 'x' inches of your max lift.

The LENGTH of you control arms is the max of your suspensions limits up or down.  Lets say you have 12 in long lower control arms.  Then the max you suspension will articulate downward (droop) is 12".  This would be the CA hanging straight down thus the max is 12 inches.

NOTE:  From level ground plane the arm can move downward the max of the length of the lower arm.  That said the arm is attached at the rear (fulcrum point) thus the arm moves downward in an arc and takes MORE than 12" of travel to move.  Arc Vs straight line distance.  In other words, it’s further AROUND than going in a straight line.

Albeit the angles are the same, the shorter the arm the faster is moves thru the arc.  Make the 'V' sign with two fingers; note how the DISTANCE from one finger tip to the other is further than the distance from knuckle to knuckle.

Easy to see how SA uses up the distance traveled quicker and the higher the lift the more the SA is angled DOWNWARD to START with.  If you had 12" SA and did a 12" lift the arms would be straight down, thus no articulation.  The solution is to MOVE the FULCRUM POINT further away, thus longer arms.

Having said that, let my punctuate with an old axiom 'there is no free lunch'.  Meaning that long arms also have their drawbacks.  The most common being a loss of ground clearance as the arm articulates downward or the loss of upward movement due to the arm running out of upward space to move.

That said, If you want to move to a LA sometime after your SA has been in place you will need: New arms, shocks, adjustable track arms f/r, possible new coil springs, new brake lines, etc.

A lot of this more or less depends on whether or not you raise your Jeep in the process of going LA.In fact, you can go LA and change nothing but the arms themselves.

Other than the fulcrum, point it’s about all is the same, but by moving that fulcrum point deeper into the center section of the rig, you slow down the speed of the arc as the arm articulates. Or another way of saying the arc of the LA is wider and the SA is quicker or much tighter.

Place a dime and a quarter on a piece of paper and draw a circle around the edge of each. The dime is a SA whereas the quarter is the LA, based upon the center to the outer edge of each which represents the length of the arm.

The LA will allow you to lift higher and not shorten your WB as quick or as much.There is a lot more, but I need a chalkboard and your presence to go much deeper. Suffice to say, 4 inches or less and LA/SA are about the same, beyond 4 inches and you need to consider LA.

LA does give a better highway ride. That said if you want a better ride either put about $4k worth of the airbags all the way around or use the money as a down payment for a Caddy.Note: The FartSac suspension is a whole ‘nother thread.

If you plan on lifting more than 4 inches, then go LA, the advantages outweigh the disadvantages, well almost...don't forget CoG.

On the other hand, if you really do not want to lift beyond 4 inches then the LA provides very little advantage at a greater expense.

Recommendations:

1)  Up to about <2.5 in MAX the OEM CA arms will suffice

2)  Up to about 3 in MAX adjustable lowers, OEM uppers

4)  3 - 4.0 MAX upper/lower adjustable CA (> 3.5 in of lift and short arms are worthless)

5)  >4.0 in long arms

I fully endorse, recommend, and run JKS Control arms.  The recommendation is based upon their use and performance characteristics.  Other CA may provide a different set of results.

Finally, lets address ‘droop steer’:

Droop steer is a progressive thing and increases in direct proportion to the amount of droop.What happens is the TB which swings down, like control arms, but does it towards the drivers side of your rig forcing your axles outward.

Things might not be so bad but the f/r axles don't work in tandem with each other.The result is your rear axle might be several inches out to the left of your rig whereas the front axle is dead under.

direction of movement:^

Front axle track:    ||<

Rear axle track:                      >||

The front axle droops to the drivers side.  The TB's fulcrum point is at the frame thus the TB drop down and to the left (drivers).

Jeep designed it this way to offset each axle under off road and on road conditions instead of both axles moving in the same direction away from the Jeep.  If it did this would make the Jeep VERY unstable in off camber situations on the opposite side of droop.

The rear axle fulcrum point is also at the frame on the passenger side thus is drops and swing to the passenger side

Bottom line is the rear of your rig is going in one direction and trying to pass you while the front end is also trying to go forward but on a different track.What is happening is it is stressing your driveline in an angular direction.Like so.  \  \

Hard on your rig!Moreover, this binding is a major contributor to the vertical bouncing in the rear that soon will show it ugly head and wreak all havoc, most often resulting in breakage and catastrophic breakage.

What the other suspension mods do is remove the TB and allow the rear to follow the front more closely and keeps the track line under the rig.

Now consider the addition of long arms with their significant droop and the resulting angularity and catastrophic failure path.

Go high (>3.5 inches), go long arm, then go tri-link for sure.  Rig will perform better AND suffer less breakage in the long run.  NOTE:  Tri-link at any juncture of suspension build from stock to not will provide benefits on and off road.

That said you might want to consider some other factors such as Center of Gravity and Weight Distribution and how it affects your off-roading.  You might want to review this article:  

Nth Degree on CoG & WD

It is not how high you lift it, but how you lift it high.

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