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01 control arm comparison lead photo

What to Look For in a Control Arm

Rubicon Express Jeep Wrangler TJ Upgrades

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.

02 rubicon express control arm comparison

There is no comparison in strength between the factory stamped-steel arms and the new Rubicon Express arms. JK and JL Wranglers do use boxed tubing control arms instead of stamped steel, but they still are not as strong as aftermarket arms from Rubicon Express.

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.

03 rubicon express control arm flex joints

Rubicon Express offers their control arms with either Super-Flex Joints or Super-Ride bushings. The Super-Ride bushings are less expensive and do a better job of insulating vibration, but they are not rebuildable and don’t provide as wide a range of motion as the Super-Flex bushings.

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.

04 rubicon express control arm adjustable length

We measured the arms relative to the stock arms and then extended them all by the same amount to relocate our front axle forward. The final step is going to a quality shop like 4Wheel Parts that is accustomed to working on lifted vehicles for a four-wheel alignment.

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.

05 rubicon express control arm flex pinion angle

The adjustable rear lower control arms from Rubicon Express allowed us to dial in the perfect pinion angle to ensure that we didn’t have any driveline vibrations. We did the same thing in the front using the Rubicon Express adjustable upper front control arms.

06 rubicon express control arm installation

We installed our control arms in the driveway with a floor jack and a pair of jack stands. We recommend swapping out the arms one at a time to ensure that the other arms keep the axle in position while you are changing out that one arm.

07 rubicon express control arms

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. 

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