A control arm is a hinged suspension link between the chassis and the suspension upright or hub that carries the wheel. It is also called an A-arm.
Control arms control the motion of the wheels so they’re in line with the body of the car.
Where the shock’s purpose is to hold everything up, the control arm basically absorbs the road. It’s what helps to give way. It moves up and down so that the tire can travel. When you hit a bump, the control arm compresses the weight and then comes down on it. It keeps the bottom of your tire in their place.”
Auto experts say control arms connect the car’s suspension to the frame of the actual vehicle. They are connected to the frame through a component known as bushings. They attach to the suspension through the ball joint. That allows the vehicle to turn its wheel as well as pivot, connecting the tire to the car’s suspension.
Cars typically have two to four control arms which depend on whether the vehicle’s suspension system has struts or shocks. Many of today’s cars only have control arms in the front suspension.
Some vehicles have upper as well as lower controls arms, although auto experts say most cars today only come with lower ones because of the way the strut assembly is designed.
Cars with upper and lower control arms are known as double wishbone suspension, in which the arms work parallel to each other.
Signs Control Arms are Wearing Down
1) Like any car component, over time, control arms wear down and have to be replaced. Many control arm assemblies wear down in every 90,000-100,000 miles.
2) Control arms can bend or break while driving over large potholes or bumps, while bushings can also wear out on their own.
3) People will start seeing tires not wearing properly. If you get tire wear, you might need to look at the components.”
4) Auto experts say other common signs the control arm assembly have to be replaced is if the steering wheel is vibrating or there is banging noise while driving over bumps.
How to Replace a Control Arm Assembly
A) Raise your vehicle
- Floor Jacks
- Jack stands
- Wheel Chocks
Note: Make sure you use jack and jack stands with the appropriate weight capacity to lift and support your vehicle. If you are not sure of your vehicle’s weight, check the VIN label which is usually located on the inside of the driver’s door or on the door jamb itself for your vehicle’s Gross Vehicle Weight Rating (GVWR).
Step 1- Locate your vehicle’s jacking points.
• With most vehicles being low to the ground and consisting of large trays or belly pans under the front of the car, it is best to do one side at a time.
• Jack the vehicle up at the recommended jacking points instead of trying to raise it through sliding the jack under the front of the car.
Note: Some vehicles have a clear marker or cut out under the sides of the car found near each wheel to indicate the proper jacking point. If your vehicle does not have these indications, just consult your owner’s manual for the proper jack point locations. As you are replacing suspension components, it will be safer if you do not lift the vehicle from any suspension points.
Step 2- Secure the wheel.
• Position the wheel chocks or blocks, in front of and behind at least one or both of the rear wheels.
• Raise the car slowly till the tire just loses contact with the ground.
• Once you get to that point, find the lowest point underneath the car where you can place a jack stand.
Note: Make sure you place each jack stand in a strong spot such as under a cross-member or chassis to support the car. Once positioned, just slowly lower the car onto the jack stand using the floor jack. Do not fully lower the jack and make sure to keep it in the extended position.
B) Replace the control arm
- Ball joint separator tool
- Breaker bar optional
- Ratchet / sockets
- Replacement control arm(s)
- Wrenches – open/box end
Step 1- Remove the wheel.
With ratchet and socket, loosen the lug nuts on the wheel. Carefully remove the wheel and keep it somewhere aside.
Step 2- Separate the ball joint from the hub.
Choose an appropriate sized socket and wrench. The ball joint has a stud that extends into the wheel hub and is secured through a nut and bolt which need to be removed.
Step 3- Separate the ball joint.
• Put the ball joint separator between the ball joint and the hub. Give it a tap or two with the help of a hammer.
• Don’t worry if it takes a few good whacks to separate them.
Note: Age and mileage sometimes make it difficult to separate them.
Step 4- Separate the control arm from the cradle.
• In some vehicles, you can remove the control arm bolt with a ratchet/socket on one side and a wrench on the other. Others might require you to use two wrenches due to space limitations.
• Once you remove the nut and bolt, the control arm will pull out. Use a little muscle for removing it, if needed.
Step 5- Install the new control arm.
• Install the new control arm in the reverse order of the removal process.
• Bolt up the cradle side of the control arm then bolt the ball joint into the hub, making sure to push it as far as required before tightening the bolt.
• Reinstall the wheel and lower the vehicle as soon as the control arm is properly secured. Repeat the process on the opposite side, if required.