Vehicle Control Arm – Everything You Should Know

A control arm is a vital component of a car’s suspension system that carries out different functions, and you can find it in virtually all cars and automobiles.

It is also known as ‘A-arm or a wishbone due to its shape.  Control arms are found in nearly every vehicle and automobile on the road.

In this article, we are going to discuss everything you need to know about the control arm, Its functions, and also how you can go about fixing this critical component of your engine when it gets bad.

This article aims to ensure safe driving and smooth rides because a bad control arm can affect both safety and drivability.

Control Arm Design

The design of control arms changes at the same rate as automotive design and manufacturing technologies.

Most vehicles feature a “double-wishbone” suspension, composed of upper and lower control arms shaped in the same way as a wishbone.

Control arms are also known as “A-Frames” or “A-Arms,” depending on whom you spoke to. Wishbones, which look similar to the letter “A,” is a type of bone found in birds.

Because this control arm shape and design works well, it is widely used in modern vehicles.

Types Of Control Arm

Types Of Control Arm

There are 3 types of control arms, the lower control arm, upper control arm, and adjustable control arm

1. Lower Control Arm

Lower control arms is used only if a vehicle has “MacPherson-strut front” or rear suspensions.

Hence, since the strut replaces it, it doesn’t require an upper control arm. In other words, an upper control arm is not needed, and there are no need for rubber control arm bushings.

2. Upper Control Arm

Any type of control arm can be used to connect the rear axle to a vehicle with a solid axle. You can often see about three to four control arms with rubber bushings at each side.

The upper control arm is also called ‘trailing arms’ and ‘rear-trailing arms.’ If the car has an independent rear suspension, it can feature trailing or upper & lower control arms.

3. Adjustable Control Arm

As its name implies, adjustable control arms are significantly used to adjust the wheel camber. The camber is the vertical alignment of the wheels.

A negative camber shifts the top of the wheel to face the center of the vehicle. On the other hand, camber is positive if the top of the wheel is positioned outside the vehicle’s center.

Adjusting a camber is very important, especially for racing, stance, and bringing down or high-jacking of a car.

Control Arm Functions

What does a control arm do in an automobile? The control arm serves several purposes, they are.

1. It connects the wheel to the frame

Amongst others, the control arm connects the wheel of a vehicle to its frame, thereby improving stability. It enhances easy riding on rough patches.

It also plays a crucial role in dampening vibrations by synchronizing the wheel movements with the vehicle frame. It has jointed edges, which help them to carry out this task.

2. It Enhance vehicle control

A vehicle’s control arm also helps rotate the steering wheel at the ball joint, allowing the driver to direct the car when driving.

It helps to move the vehicle up or down while keeping it stable and touching the ground. In this case, you won’t notice any sign of bumps and potholes.

The lower and upper control arms play a similar role in ensuring that a vehicle is easily controlled and smoothly ridden.

Control Arm Problems

Control Arm
Credits: Greg Brave / Shutterstock

As much as the control arm of a car is very important in its smooth ride and control, certain issues are associated with it.

For instance, the wear-off of the control arm bushings can cause the metal components to scrub themselves. Again, there could be a rusty or worn-out ball joint, thereby causing too much play.

Then, the drivability issues occur due to the main body rusting, tweaking, or breaking.

The following is a list of the different components of a control arm and their potential problems.

1. Main Body Damage

This is one of the most common problems associated with a control arm, although it depends on the kind of material used for the body. Constant exposure to water or moisture for a long time could spell danger for the control arm body, causing rust.

Rust is not a good phenomenon, as it can damage the control arm’s structural integrity and strength. With rust at both ends, changing the parts will be difficult. If the damage is too severe, it could crack, tweak, or break the control arm’s body.

Problems like collisions, too much abuse of vehicles, or wheels hitting a curb can easily occur. Finally, poor fastening of the control arm during towing activity can result in severe damage.

2. Control Arm Bushings Wear

As much as control arm bushings are rubber-made, they’re always prone to wear and breakdown.

Perhaps the bushings have loosened, resulting in metal parts of the suspension coming into contact whenever they are frequently used.

Worn-out control arm bushings tend to be loose, which prevents the control arms they connect to from moving freely.

In this case, they fail to absorb vibrations to minimize noise, resulting in rough driving and difficulty in vehicle control. Again, while driving, the car often releases frustrating and unusual sounds.

3. Control Arm Ball Joints Damage

The control arm ball joint is located at the edge of the control arms, connected to the steering knuckle or wheel assembly.

While several control arms have a permanent or built-in ball joint, others come with a separate joint.

The ball joint must be permanently attached to the control arm. Otherwise, it will break, leading to severe problems for your car.

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Bad Control Arm Symptoms

Bad Control Arm Symptoms

The following are some common bad control arm symptoms.

1. Vibrations

Whenever the control arm wears out, you’ll begin to experience vibration with the wheels. The wheels will also shimmy when reversing.

In other words, the steering wheel will vibrate when reversing. Once your steering wheel tingles, make sure you inspect the bushings immediately to check for possible damage.

There are also other parts of your car that can cause vibration. Therefore, before rushing to a conclusion, make sure that none of the other parts are involved since vibration is just one of the symptoms of a bad control arm.

2. Wandering Steering Wheel

One of the most significant symptoms of a bad control arm is a wandering steering wheel. The steering wheel moves from one side to the other with vibrating signs and faulty control arms maker aside.

If you encounter a wandering steering wheel, it indicates too much movement or worn-out bushings and ball joints.

Therefore, it is a sign that the control arm is faulty, and failure to change the defective parts as soon as possible will make the driver uncomfortable and make him lose control of his vehicle.

3. Unusual Noises

Unusual noise is one of the bad control arm symptoms. This sign is indicative of excessive wear of control arm bushings or ball joints.

Bushings help halt the control arm in motion, while ball joints help it rotate. If they are worn out, it could increase the movement and knock the metal components of the joint.

These activities will produce sounds in the suspension, particularly during acceleration, going around curves, or driving in challenging road conditions.

If a control arm is bad, it can cause a popping or snapping sound, or even a clicking sound whenever the vehicle comes to a halt.

At first, you might be tempted to ignore the sounds since they’re very minimal. However, if you do nothing about it, the noise will increase in its intensity and develop more bad suspension components symptoms.

4. Wobbly Wheels

Another symptom of a bad control arm is a wobbly wheel. If the wheel hub is bad or damaged, it can also cause the wheel to wobble.

Remember, a control arm connects the wheels and chassis to a vehicle. Therefore, the wheels will not rotate in a plane when they’re not connected to the chassis.

Again, a wheel will experience a wobble when the bushings are worn-out or if the control arm tweaks or bends. Driving at high speed while having a wobbly wheel is dangerous and affects your ability to drive.

5. Sudden Change in Braking

Even though it sounds strange, a bad control arm can improve braking performance, especially when you didn’t expect it to.

This symptom often occurs if the bushings become faulty and stop the control arm from moving back and front.

Nevertheless, it often improves temporarily and doesn’t happen every time you touch the brake pedal.

Failure to address the issue will cause dreadful brake performance, leading to driving insecurity. Therefore, you’ve to sort out the problem immediately when you notice it.

6. Steering Wheel Pulling To The Side

The control arm plays a crucial role in providing efficient steering and helps in the up and down movement of the vehicle’s body.

As a result, if it is faulty, it will not function properly, and the car will be pulled to one side while driving; at this point, you need to force it back in line.

Other parts could also cause this problem, for instance, if the control arm is damaged. Therefore, you need to check the control arms on each end for clarification. If the steering wheel is stiff, the ball joints are dry.

Lack of lubrication can also halt the free movement of the control arm, and it will cause difficulty in steering, which is a big problem regarding driving and safety.

Joint lubrication will solve the problem if the joint is not worn out and does not show any ill signs.

7. Uncomfortable Rides

The control arms are hinged on bushings which dampen vibrations and minimize the impact of bumps or rough terrain.

If these parts are bad, any passenger you are carrying will feel the gallops and potholes on the road.

Faulty control arms can make a vehicle lean very heavily at corners, especially sharp ones.

Whenever the car moves on from a fixed point, its rear will go through a backward movement, thus, giving you a sign that your control arm is bad and needs replacement.

8. Uneven Tire Wear

Several things can cause uneven tire wear, one of which is a bad control arm. When wear is detected on the inner edges, it indicates worn bushings or ball joints.

If a control arm bends or tweaks, it can cause uneven tire wear. Once there’s a little bend in a control arm, you’ll hardly spot it. But with the bushings or ball joints, it’ll be clear.

You can discover this through correct measurement. If your control arm or its hinges is bad, it could result in uneven tire wear. It could also affect the bushings or ball joints, indicating that the control arm has a problem.

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How To Replace A Bad Control Arm

A bad control arm will most likely require a replacement when it gets bad. It’s hard to repair worn ball joints and bad bushings.

There’s only one way you can fix a tweaked or damaged control arm, and that is by replacement. It can cost you approximately several hundred dollars to replace a control arm. Below are the items you’ll require;

These are the items you’ll need.

  • Your new control arm(s)
  • Floor jack and jack stands
  • Ball joint separating tool
  • mallet
  • Crowbar
  • Breached bar
  • torque wrench,
  • Sockets and ratchet wrench
  • Clean brake and penetrating oil.

Follow these steps to know how to replace your control arm

  1. Find a spacious and secured place and unbolt the nuts to enable you to detach the wheel.
  2. Gently raise the car and remove the wheel to replace the control arm.
  3. Locate the position where the control arm is linked to the ball joint. Meanwhile, the joint connects the steering knob to the control arm. You’ll need to detach the control arm from the ball joint forcefully. Then, apply penetrating oil to the bolts you wish to loosen so you can easily undo them.
  4. Get rid of the cotter pin and the castle nut that pivots the ball joint to its control arm. If you can remove the ball, raise it from its position using a ball separator tool and a hammer. If a press is available, you are free to use it. Take out the bolt that connects the ball joint to your steering knuckle if you can’t remove it.
  5. Unscrew the bolt that holds the control arm to its frame with a wrench. Then, gently pull out the control arm by separating it immediately after the bolts have been pulled out. Double wishbone suspensions come with the upper control arm. Hence, that is the best way to remove it.
  6. Remove the bolt that holds the upper ball joint in its position.
  7. With a crowbar, raise the ball joint out of the steering knuckle.
  8. Loosen one part of the upper control arm joined to the vehicle frame. Then, using the separator for the ball joints, disconnect the ball joint from the control arm. There won’t be any disconnection if the ball joint is permanently built.
  9. Position the lower control arm in its perfect location on the vehicle’s frame, put in the bolts with your hands, and fasten them appropriately.
  10. Raise the control arm and install the ball joint at its end inside the steering knuckle. Using the opposite method, you can use your hands to fix the castle nut before replacing the already detached upper control arm. Make sure this is done before you tighten your lower control arm.
  11. Insert the nuts and bolts where necessary and lower the car to enable you to replace the wheel. You are free to test your work by driving the vehicle to ensure that you’ve perfectly mounted or installed the control arm.

Note: Some vehicles have ball joints and control arm bushings that can be replaced. Replace them if this is the case.

Watch this video to see how you can replace control arm

Frequently Asked Questions

What is a control arm?

The control arms form the basis of a suspension system. They connect the front wheel assemblies to the vehicle’s frame. The control arms enable a driver to drive a car and also guide the wheels along the road surface.

Is a control arm a wishbone?

The control arm is also known as the “A” arm or even a wishbone because of its shape. Control arms look like wishbones, as you can see from the name.

Can control arms cause death wobble?

It is a fact that components eventually wear out. A loose track bar bushing or control arm can cause death wobble. Your Vehicle could also be affected by loose bolts or bent control arms. Keep an eye on your track bar and control arms to prevent this.

How much does it cost to fix a control arm?

On average, control arm replacement costs between $120 and $200. Parts can cost between $50 to $100, and labor costs range between $80 to $150. This price range does not include taxes or fees and does not take into account your vehicle model and location. Other repairs might also be required.

How long do control arms last?

The control arm assembly can wear or become bent over time. They usually wear between 90,000.00 and 100,000 miles. These assemblies can be damaged faster if they are hit by a car or go through a pothole. You may also experience wear in other parts of the assembly, like the bushings and ball joints.

Can you drive with a broken control arm?

If an arm is broken, the car cannot be driven safely. don’t try to drive a vehicle with a broken control arm until it is replaced. You will have less weight support, and the stability may be compromised if the control arm breaks.

Is it okay to replace only one control arm?

While it is possible to replace one control arm or all of the upper arms, it is not advisable. Control arms often wear at approximately the same rate. It is a good idea to replace both control arms if one is damaged and the other is in its final stages.

The control arm is a hinged suspension link between the chassis and the suspension upright or hub that carries the wheel of a vehicle.

Control arms enable a driver to control the car and also guide the wheels along the road surface. Although they look simple, control arms play a crucial role in vehicle stability and drivability.

Although they may not be the most complex or fascinating components of a vehicle’s design, control arms are crucial to its operation.

These arms are designed to handle steering inputs from drivers and road surface fluctuations. They are essential to vehicle ride, handling, and drivability.

Scott Greene is a seasoned automotive technician for over 5 years and has been deep into advanced automotive diagnostics for a couple of years. He Loves writing about Automotive Diagnostics and Repair, Trouble codes, Buyer guides for various car parts and accessories, and lots more. 

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