Some well respected manufacturers feel the stock control arms on the JK are already long enough to support a 3-4" lift and stout enough for most off road conditions. They are much longer and sturdier than those originally found on my previous TJ. So... why should I pay the additional cost of a premium kit that includes upper and lower control arms? Are they really a vast improvement? If adjustability is the issue, couldn't I simply use an adjustable upper arm only?

 

On the TJ the CAs were short, so when a lift a kit was installed the CAs were positioned at a relatively steep angle, so the solution was to install long arm kits.

Many of us agree with those well respected manufacturers. The CAs on the JK are long enough to accommodate a taller range of lift but they are a fixed length. Most of the recommendations to replace the CAs are to install adjustable CAs, which allow you to adjust the Caster and Pinion angles.

You don't need to replace all of the CAs. You could just replace the front uppers, but most us replace the front lowers because they provide a wider range of adjustment and are easier to install.

The stock CAs are good quality, particularly the bushings, but in many cases keeping them requires using cam bolts as an adjustment mechanism, which is not an ideal solution.