What to Look For in a Control Arm
Photography by Harry Wagner
The four-link coil suspension introduced on the Jeep TJ Wrangler in 1997 (five links if you include the track bar) was a dramatic improvement over the leaf springs used on the YJ Wrangler. This same suspension is found on ZJ Grand Cherokees and the front of XJ Cherokees, and a scaled-up version was even used on Ram trucks. While this suspension offers more articulation than the leaf springs used on earlier Jeeps, there is still plenty of room for improvement. The factory control arms are relatively short and use rubber bushings at each end of the stamped sheet metal arms. These components are fine when they are new and under a stock height Jeep, but time and mileage degrade them, not to mention encounters with rocks. Lifting your Jeep makes matters even worse as the caster and pinion angles are thrown out of whack. Fortunately, Rubicon Express has what you need to get your Jeep suspension dialed in no matter what model you are driving.
Construction and Materials
The factory control arms that came on TJs, XJs, and ZJs use stamped steel that is open on the bottom. These are inexpensive to produce and lightweight, but those are the only redeeming qualities. By contrast, Rubicon Express control arms are constructed from thick wall DOM tubing. DOM stands for “drawn over mandrel” which means that it is the process from which the DOM tube is formed. DOM tubing starts with an electrically welded formed tube (ERW) and is then cold drawn through a die and over the sides of a mandrel to make it more uniform and remove the seam. This tubing is strong enough to withstand impacts and drag over rocks without concern.
Bushings or Flex Joints
The factory control arms come with rubber bushings at each end, and there are plenty of compelling arguments for using rubber bushings. They do an excellent job of damping vibrations, are inexpensive, and are durable. They don’t provide much range of motion though. At the other end of the spectrum are rod ends (aka heim joints) that provide a wide range of motion and are very strong, but are not sealed from the elements and can wear quickly. Rubicon Express Flex Joints offer the best of both worlds. A threaded steel insert allows adjustable preload and easy maintenance. The unit is greasable and extremely quiet due to the non-metallic races. This bearing allows extra flex for off-road prowess, yet does not sacrifice on-road handling or long-term durability.
Adjustable or Fixed Length
As you lift your Jeep you increase the distance between the transfer case output at the pinion yoke in the axles. The greater distance results in increased angles on the driveline. In the front, you also have to be concerned about decreased caster, which can lead to vague steering and wandering at freeway speeds. Fixed length control arms cannot remedy this issue, but they are less expensive than adjustable control arms due to their simple construction. Since the TJ platform uses four control arms to locate the front and rear axles, you can adjust caster and pinion angle with two adjustable arms and two fixed length arms.
With a normal driveline with a single u-joint at each end, you want the angle of the transfer case output to be parallel to the pinion to cancel out vibrations. A common upgrade on TJs is a slip yoke eliminator that allows for a longer driveline and is often combined with a double cardan joint (often called a CV driveline). When using this style of driveline you want the pinion to be pointed directly at the transfer case. In the front, if you have locking hubs the driveline angle is less of an issue since it will not be spinning when you are in 2WD. In this case, prioritize the caster, which should be set around 5 degrees. Too much caster can make the steering heavy, but too little caster can result in wandering on the road and even death wobble. Since TJs do not come with locking hubs, you have to find the balance between enough caster and a reasonable driveline angle. Fortunately the front driveline on a TJ is much longer than the rear driveline, making the situation easier.
The Rubicon Express control arms come with zerk fittings that allow them to be greased, ensuring smooth, quiet performance and long life. We recommend pumping some fresh grease into the fittings after each trip. Also, note how the tubing for the control arm is offset from the bushing to maximize ground clearance. This is just one of the little details that set Rubicon Express apart from the competition.