What Does a Control Arm Do? Bad Control Arm Symptoms

Understanding suspension and steering parts of your vehicle is important as failure of these parts can be catastrophic when on the road. In the best-case scenario, if your suspension system isn't working well you are in for an uncomfortable ride. The worst-case scenario is that you may lose control of your car while driving. In some instances, if parts of your suspension system are not in working order, you won’t be able to drive.

Control arms are a commonplace item in all vehicles made in the last 40 years, with only 4-wheel drive and heavy duty trucks sometimes being the one, rare exception. Understanding the role of this component in the suspension system and overall control of your vehicle can help you with the maintenance of your car.

What Does A Control Arm Do?

To keep it simple, the control arm is a link that connects the frame of the car to the wheel hub assembly or steering knuckle. Control arms can come in many different shapes in sizes, upper Control arms are often call “A” arms as they have a shape vaguely like a capital letter A. The control arm(s) move up and down with the spring when a car hits a bump or other road irregularity. This allows the tires to maintain contact with the road and, thus, control. The control arm is part of the suspension system that helps your car remain in full contact with the road at all times, that’s giving you necessary control.

In most control arms, the two lower parts of the “A” are attached to the frame via control arm bushings, which are rubber pivot-points. The top of the “A” is attached to the steering knuckle by way of a ball joint. In older vehicles, this ball joint is serviceable on its own, without the need to remove or replace the control arm. On most newer vehicles, the ball joint is incorporated into the design of the control arm, hence, the entire arm must be replaced. Vehicles can have a different numbers of control arms. Some have as few as just one lower control arm, many vehicles an upper and a lower, and some even have more elaborate, multi-link arm set-ups.

When a control arm fails, multiple things can happen. Most failures occur from the ball joint failing. Complete ball joint failure can cause a steering knuckle disconnection and loss of control of the vehicle. Control arm bushings can also wear and fail, creating clunking, wandering steering, and loss of control. Before your control arm gets to this point, be on the lookout for these signs.

Bad Control Arm Symptoms

1. Popping Noise

One of the earliest signs of a failing control arm is hearing a popping noise when you drive over road irregularities. You may also hear a popping noise when you speed up or reduce the speed of your vehicle, but normally going over bumps at slower speeds, like speed bumps is an indicator of a ball joint that is popping, or possible worn bushings.

2. Steering is Unstable

Another symptom that can indicate control arm problems is unstable steering. This is very common in failing bushings, where the alignment of the steering wanders, causes the car to veer either to the left or the right when the driver runs over a bump in the road. This issue becomes more apparent if the car is driving on uneven surfaces or unstable terrain. This symptom may also indicate that your idler arm or steering tie rods are in bad shape, so when inspecting, make sure to check the steering components.

Consistent vibration throughout the vehicle could also be an indicator that the control arm may be starting to fail, but not exclusive to this. Given that the control arm absorbs a lot of the energy and is the link between the suspension and the frame, other issues like unbalanced tires, or failing steering components will only be worse if your control arms also have weak components.

3. Uneven Tire Wear

Uneven tire wear is also a potential sign of a failing control arm, as this is an indicator of alignment issues. As control arm bushings wear, this can force the vehicle out of alignment, causing wear on the outer or inner edges of the tire. While sometimes this is just an indicator that a proper alignment is needed, it can also be caused because of worn bushings. Any alignment shop will be able to properly diagnose this. You can search here for a list of Preferred Repair Shops in your area that can deal with alignments and suspension diagnosis like control arms.

What to Do About Control Arm Problems

If you are noticing any of the above symptoms, get your car to a shop for a full suspension check. If you are an avid DIYer, get your car up on jack stands and thoroughly check out the control arms and front steering for any issues. In the event that your control arm or another suspension link or arm fails while you are driving, you want to try to slow the car down and get it off the road if you can. Remember that in the event of a complete failure of the control arm that you may be unable to steer the car.

Remember that you need to realign your vehicle after you replace anything having to do with the control arm, suspension, or steering. For any of these parts, tools, or advice, come see the parts professionals at AutoZone, which can set you up with everything you need to do the job right.

If the job is too big for you, seek out one of our Preferred Shops to help you do the job.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

FREE Loan-A-Tool® program requires returnable deposit. Please note that the tool that you receive after placing an online order may be in a used but operable condition due to the nature of the Loan-A-Tool® program.

Related Posts