Control arm: problems, when to replace, repair cost

Updated: February 18, 2017
Control arm
Control arms "hold" front wheels.

Most cars have two control arms in the front suspension. Often they are called lower control arms. Some cars (e.g. Honda Accord) and many trucks have four control arms, two upper and two lower arms. What does a control arm do? It connects the frame or body of a car to the assembly that holds a front wheel. This assembly is called a steering knuckle.

Control arms are connected to the frame or body of a car through flexible rubber bushings, called control arm bushings. This allows a control arm to swing up and down as front wheels roll over bumps and potholes. The outer end of a control arm has a ball joint.

In some cars, a ball joint is bolted to or pressed into the control arm and can be replaced separately. In others, a ball joint comes with a control arm as one piece. Control arms have a very important role holding both front wheels on the road. If a control arm is worn out, damaged or bent, the vehicle is NOT SAFE to drive.

Control arm problems

Separated ball joint
This ball joint has separated while driving

There are a few reasons why a control arm may need to be replaced. A worn out ball joint that cannot be replaced separately is probably the most common reason. A ball joint is an extremely important component. If it wears out, the front wheel can separate from the lower suspension causing the vehicle to lose control.

In the photo above, the ball joint has separated while driving, although the owner was lucky that it happened at slow speed. If this had happened on the highway, the outcome could have been much worse.

Worn out or torn control arm bushings is another reason a control arm may need to be replaced. In some cars, control arm bushings can be replaced separately, but it involves more labor and could cost more. For this reason, the whole control arm is usually replaced if the bushings are worn out.

The control arm is the most common part that bends in a collision involving one of the front wheels or after hitting the curb. A bent control arm must be replaced.

How a control arm is inspected

Technician checking the suspension of the vehicle on the lift
Technician checking the suspension of the vehicle on the lift

Control arms, as many other suspension components, cannot be properly inspected at a drive-through fast-lube place. The only way to inspect control arms is when the vehicle is lifted on a hoist. This is what happened to the owner of the vehicle in the photo above: for the last year, he visited only a fast-lube shop and they didn't catch a worn-out ball joint earlier.

Are there any symptoms of a bad control arm bushings or a ball joint? You might hear some popping or clunking noise when driving over bumps, or when accelerating and decelerating. In some cases, a car may feel unstable and "wander" during braking or when driving over rough surfaces. Often, however, the symptoms might not be noticeable at all.

This is one of the reasons why it is important to have your vehicle inspected at least once a year in a repair shop by a skilled mechanic with the vehicle lifted on a hoist.

How much does the control arm replacement cost? Is it cheaper to use an aftermarket part? Read .