What the Heck is a Control Arm?

I had never been interested in learning about fuel pumps or control arms.   Don’t get me wrong, I know what fuel pumps and control arms do, but that’s about as much as I wanted to know.  I was recently forced to learn more about control arms when I had to replace one of mine. Isn’t it amazing how you can go for so long not caring about something until it hits your wallet?  Here is a bit of information I found out after I had to put in a few hours replacing my own lower control arm.

Control arms are an important part of the suspension system.  There are several types of control arms, including upper, and lower control arms, which are located in both the front and the rear of the vehicle.  Control arms by nature must be able to handle a great deal of weight, therefore the shape and size of these units can vary greatly between models. The wide end of a control arm attaches to the frame of the car and pivots on a bushing, while the skinny end of the control arm attaches to the knuckle which pivots on a ball joint.  A two control arm set-up per wheel makes up a double wishbone suspension that is found on most modern vehicles.  On a side note, I thought it was fitting that I had to replace a part referred to as a “wishbone,” so close to Thanksgiving.  Alright, I am getting hungry again; let’s get back to these control arms.  When there is only one control arm per wheel, than that control arm is most commonly the lower part of a MacPherson strut suspension system.

Like most suspension components, control arms allow for a smooth ride even over a rough surface. This explains why it felt like I was driving over invisible speed bumps. The control arm assemblies were designed to attach the suspension to the vehicles while using bushings to cushion the impacts taken by the wheels.  The reason there are usually two control arms per wheel is to add stability, and secure the wheel as the car travels over uneven surfaces. Think of it like a wheel barrel, which is a lot easier to keep going smoothly when you have two handles to grasp onto.  Imagine how much more difficult it would be with only one handle.  Though, not all cars have two control arms per wheel.  Front wheel drive vehicles that have strut assemblies instead of shocks usually have the lower control arms, but not the upper.

Control arms need to be inspected on a regular basis and serviced if damage or cracking has occurred.  Make sure to have them inspected regularly so you don’t have to blow another Sunday in the garage instead of on the golf course. If you don’t properly service them, the control arms can prematurely fail which will cause the handling of the car to become erratic and unsteady. Just like driving on the golf course, this can raise your handicap by about two to three strokes.  A sure sign that a control arm bushing is worn out is a knocking sound when driving over bumps, or when turning the steering wheel back and forth.