What is a control arm on a car?

The control arm is an essential part of your suspension system that provides good road holding. It connects the chassis to the wheel. Your vehicle has at least one control arm for each wheel. The control arm is not a wearing part, but it can be damaged by impact.

What is the purpose of the control arm?

The control arm is the auto part that connects the car chassis to the wheel. It's usually located at the front of the car. In fact, it's the silentbloc that connects the control arm on the chassis side to the suspension ball joint on the wheel side.

It's thanks to the front and rear control arms that your car has good road holding. Control arms need to be strong enough to withstand bumps and road imperfections. For this reason, they are usually made of cast iron, aluminum, or steel.

There are two types of control arms: the wishbone control arm and the McPherson control arm.

Types of Control Arms?

Lower control arms

When a vehicle is equipped with a MacPherson strut-type front or rear suspension, only lower control arms are used. The upper control arm is not needed because the strut takes its place.

Upper wishbones and trailing arms

At the rear of a solid-axle vehicle, any type of control arm can be used to connect the rear axle to the frame or monocoque. Most are three or four control arms with rubber bushings at each end. These control arms are called "trailing arms" or "rear trailing arms". Only one vehicle has an independent rear suspension; it may have upper and lower control arms, trailing arms, or some other unique design that matches the shape of the vehicle.

Adjustable Control Arms

Adjustable control arms are used to adjust the camber of the wheels. Camber is the vertical alignment of the wheels. Negative camber means the top of the wheel is tilted inward toward the center of the vehicle. Positive camber means the top of the wheel is tilted outward, away from the center of the vehicle. Camber adjustment is an important factor when driving, positioning, lowering or lifting a vehicle.

Signs that a car's control arm is out of alignment

1. Noise

When you drive your car over a bump or mud in the road, you'll hear a thud. You may also hear a rattle or thud as you turn corners, especially at low speeds. The control and smoothness of your ride will deteriorate when the control arm is worn out, and you'll inevitably notice a reduction in the quality of your driving experience.

2. Motion

Too much wheel movement is another obvious symptom of a failing control arm. Use a floor stand to lift your car so that one of the wheels is completely in the air. When you put your hands on the wheel and push, you'll feel a wobble. This is similar to the symptoms of a bad CV or ball joint. There should be no more play in the wheel than is acceptable, so if you feel too much movement, check the car.

3. Steering Wobble

Driving at higher speeds between 45 and 60 mph will demonstrate control arm failure by showing a wobble in the steering wheel. This is similar to when the tracking and balance are off and the steering wheel drops sharply as you drive. It's best to check for misalignment, uneven tire wear, or bent wheels first, but if you've checked these things recently, the control arm is probably the cause.

How do I replace a control arm?

Want to replace a control arm on your car? Here's a step-by-step guide to help you replace the faulty control arm on your car.

Step 1: Mount the car on jacks

Start by jacking up your car. Remember to lift your car on a flat surface to ensure its stability throughout the procedure.

Step 2: Remove the wheel

Once the car is raised, you can remove the wheel on the desired side.

Step 3: Unscrew the Control Arm Mounting Screws

With the wheel removed, you finally have access to the car's suspension system. You can now remove all of the control arm mounting bolts.

Step 4: Remove the HS wishbone

Once all of the control arm mounts have been removed, you can remove the control arm. Depending on the type of control arm, the number and location of mounting bolts may vary.

However, the procedure is the same in all cases. In some cases, you can use a wishbone lever to help remove the wishbone.

Step 5: Install the New Control Arm

Install the new control arm by tightening the wheel and frame side mounting bolts. Do not completely tighten the mounting bolts yet. Be careful to position the control arm correctly without damaging the flanges.

Incorrect installation can seriously affect your safety on the road and the life of your suspension and tires. Replace the wheel and finish tightening the control arm mounting bolts.

Important: Do not tighten the control arm mounting bolts until the wheel is on the ground. Tightening the bolts with the shock not deflected will subject the control arm flanges to high torsional forces, which will damage them very quickly.

Step 6: Check Wheel Alignment

As with most steering and suspension modifications, it's important to check the alignment of your wheels after replacing the control arms.

This is because the wheels may no longer be properly aligned. Incorrect wheel alignment leads to premature tire wear and loss of traction.

Note that each vehicle has three or four control arms in the suspension system, including upper and lower control arms. To determine which control arm is causing the problem, you must examine the suspension to inspect each part more closely. Repairing the upper or lower control arms may require a bit more skill, so you may want to seek professional help if you're not familiar with more complex automotive repairs.