What exactly is a long arm or short arm lift? I couldn't find anything in the FAQ describing the diffference. Thanks in advance.

 

Look under your Jeep. You will see "arms" that connect from the axle to the frame, 2 at each corner. They act as pivots and move up and down as your suspension travels up and down, keeping the axle where it belongs.

A regular or short-arm lift retains these stock arms, while a long-arm lift replaces these arms with longer units that reach further from the axle and must be attached to the frame closer to the center of the vehicle.

When you lift the vehicle too much, the stock arms get closer to a vertical position, which will not respond as well going over bumps and terrain, as they won't pivot up and down as easily. They also will be pulling the axle more toward the center of the vehicle, which may cause clearance issues and rubbing, as well as messing up your spring perch alignment. That's why the larger and/or more premium lifts are long arms systems.

Long arm systems are expensive, and often labor intensive. There are a few bolt on systems, but most involve cutting or grinding off the old control arm mounts, and welding on new mounts in the proper location on the frame.

One nice feature of the JK is that it has longer stock arms than previous models, so you can get away with a little more lift before needing a long-arm kit than on the prior models.

Everything make sense?

 

Makes sense. Thank you very much.

 

A followup question which may be off topic, but how does that relate to some lifts being 3-link and some being 4-link? I conceptually understand the difference, but I don't understand the advantage or disadvantage of one over the other.

 

No problem.
After re-reading my post I should clarify one thing. Short-arm kits may not always use the stock arms. Many come with new arms that still use the stock mounting points, but will be a slightly different length or adjustable to fine tune the axle location and caster angle.
Even though the arms are new, it is still a "short-arm" because it uses the stock control arm mounting locations.

 

Good question. That's something I'm not familiar with, but I think it has to do with REALLY big lifts on trucks. Like so much that they have to ditch the leaf springs entirely and put in a new custom setup... Maybe somebody else here has experience with these?

 

Each link constrains movement of the axle in a given direction.

The JK is a 5-link system (per axle):

The 2 lower control arms provide longitudinal stability (prevent fwd-aft motion)
The 2 upper control arms provide resistance to the torque and braking
The track bar provides lateral stability (prevent side to side motion)

The 5-link system provides the greatest potential for long suspension travel, but the 5th link over-constrains the equations of motion which creates other challenges.

In the case of the 4-link suspension, the upper CAs are positioned at an angle to provide lateral stability. This design has a limited range of effective suspension travel because of the horizontal and vertical coupling provided by the angle on the upper CAs.

In this case, a 3-link suspension combines the upper and lower arms into something known as radius arms. This design is hotly debated in a current thread you can readily find using the SEARCH button for "radius arms".

This may sound like a lot of options, but there are many more when you consider independent suspension, leaf springs, trailing arms, etc, etc, etc

And to think this all got started a few thousand years ago when "man" (so the stone markings indicate) invented the wheel.

 

Look here:
http://www.teraflex.biz/category/tech/faq/
or directly
http://www.teraflex.biz/tech/faq/sho...r-tjs-and-jks/