Each control arm is connected to the vehicle frame with two control arm bushings. These bushings allow the control arms to move up and down. The opposite end of the control arm is attached to a steel spindle. The spindle is what the front wheel is bolted to. On non-strut equipped vehicles, the spindle is attached to both the upper and lower control arms with a ball joint.
The ball joint is a steel ball enclosed in a steel socket that allows the spindle and front wheel to rotate left and right and allow the wheels to move up and down following the roads surface.
Sandwiched between the control arm and vehicle frame, positioned in a spring socket, is a heavy steel coil spring that supports the weight of your vehicle and provides a cushion against bumps. To combine the two opposite motions on each end of the control arm, the arms are tied on the frame side to pivot up and down on the control arm bushings. On the opposite end, the control arm is tied to the spindle and front wheel with upper and lower ball joints.
The coil spring supports the weight of the car and dampens the shock of road surfaces. They cushion the suspension system which in turn controls noise and vibrations, and also provide a softer ride over bumps. Bushings can flex and move while retaining stiffness and the ability to return to their original shape and position. Many suspension and steering joints utilize bushings when components need to be mounted together where vibration is a concern.
Bushings are used in control arms, shock absorber mounts, stabilizer bars, stabilizer links, engine and transmission mounts, and other suspension and steering components. Bushings have a function similar to cartilage in joints of the body. Worn or damaged cartilage results in bone on bone contact and discomfort. Worn or damaged bushings can allow metal on metal contact, tire wear, discomfort, noises, and vibrations.
Bushings deteriorate due to heat, age, exposure, heavy loads, salt, oils, and the stress of frequent movement. Like the ball and socket joint that connects and holds your leg bone to your hip bone, a ball joint connects and holds the front suspension of your vehicle together.
In the same way your leg can move up and down, and side to side, a ball joint enables the wheel and suspension to move together in the same manner. Ball joints allow a limited range of movement in all directions and are the pivot between the wheels and the suspension. A single ball joint is used to allow free movement in two planes at the same time, including rotating in those planes. Combining two such joints with control arms enables motion in three planes, allowing the front end of an automobile to be steered and a spring and shock suspension to make the ride controlled and comfortable.
There are two kinds of ball joints. Ball joints are classified as either load-carrying or follower types, and their position in the suspension varies depending on the suspension design. Load-carrying ball joints are designed to support the weight of the vehicle while providing a pivot point for the steering system. Follower ball joints are designed to maintain precise dimensional tolerances as well as a pivot point for the steering system.
These two types of joints often have different wear and failure rates, with the load-carrying joints usually failing first. Many currently manufactured vehicles worldwide use a MacPherson strut suspension, which utilizes one lower control arm and one lower ball joint per wheel with the necessary small amount of movement at the top of the strut usually provided by an elastomeric rubber like bearing, within which is a ball bearing to allow free rotation about the steering axis.
In this design, the lower ball joint is a follower, with the bottom of the strut connected directly to the steering knuckle and wheel. The bearing plate of the upper strut mount carries the vehicle's weight, leaving the lower ball joint to act only as a pivot point.
In a non-MacPherson strut automobile suspension, the two ball joints per wheel are called the upper ball joint and the lower ball joint.
In the majority of these designs, the coil spring is seated in the lower control arm, supporting the weight of the vehicle. The lower ball joint is the load-carrying joint in this type of suspension, while the upper ball joint is the follower, with no significant load to support. It acts only as a second pivot point for steering. Most modern ball joints are sealed and do not require lubrication as they are lubed for life.
Each control arm is connected to the vehicle frame with two control arm bushings. These bushings allow the control arms to move up and down. The opposite end of the control arm is attached to a steel spindle.
The spindle is what the front wheel is bolted to. On non-strut equipped vehicles, the spindle is attached to both the upper and lower control arms with a ball joint.
The ball joint is a steel ball enclosed in a steel socket that allows the spindle and front wheel to rotate left and right and allow the wheels to move up and down following the roads surface. Sandwiched between the control arm and vehicle frame, positioned in a spring socket, is a heavy steel coil spring that supports the weight of your vehicle and provides a cushion against bumps.
To ensure that the control arms, bushings and ball joints are in perfect alignment, some control arms include adjustable attachment points at the frame. When necessary, a mechanic can align the front end and keep your car driving straight down the road.
Learn more about quality steering and suspension parts , find your car part , or find where to buy your auto part today. The content contained in this article is for entertainment and informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic.
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