Auto axle suspension parts

Axle suspension: key insights into component performance, mounting, diagnostics, and durability

Suspension parts are the elements which connect the car’s body or frame to its wheels or beam axles and provide a relative movement between them. They define how the wheels can move in relation to the vehicle body. They prevent body roll on cornering and stop excessive squat and dive during acceleration and braking.

Suspension design

The main suspension parts are arms, rubber bushings, ball joints, and fasteners.

An arm is a robust rod or an A-, L- or H-shaped component with a corresponding number of attachment points. They are connected to other elements either rigidly with a threaded joint or via rubber-metal bushings or ball joints. The latter are used in the assemblies where the connected elements need to be able to rotate.

For example, the MacPherson suspension features a single arm with three attachment points. It is attached to the body by rubber bushings and to the steering knuckle by a ball joint.

Bushings are bearings made of rubber and metal which, in addition to connecting suspension parts, can absorb vibrations which occur between them and enable the connected elements to move a little. Most often, they consist of a rubber flexible element with one or two metal sleeves.

Ball joints have a robust metal housing with a polymer bearing and a ball stud inside. There is a dust boot where the stud exits the socket. Such a ball joint design allows the connected parts to rotate in different planes.

Maintenance advice

• Avoid aggressive driving, especially on poor-quality roads.
• Keep vehicle parts clean. Dirt is one of the things which encourage corrosion.
• Replace faulty suspension components on time. For example, a bad shock absorber increases the risk of the arm cracking when driving over an obstacle.
• When repairing or servicing your vehicle, never put a jack under suspension arms.
• Do not overload your vehicle. Its suspension components are designed for a particular weight.

Symptoms of malfunction

If suspension arms are deformed, the car may pull to one side. Wheels become misaligned. You can notice uneven tyre wear and characteristic bumps to the vehicle underbody when a wheel goes over a dip or obstacle. You may see that one of the wheels has shifted in the wheel arch. In the worst cases, the chassis may be deformed. The same symptoms occur when bushings and ball joints are worn out. However, these malfunctions usually come with knocking and squeaking sounds and vibration.

Causes of malfunction

Strong impacts when driving over bumps and potholes or hitting a kerb often deform the arms. In some cases, the components may even crack. As for the bushings, their premature wear usually stems from incorrect pressing in and loose or overtightened threaded fasteners. The rubber element loses its elasticity when exposed to aggressive chemicals such as thawing agents. Torn dust boots are especially dangerous for ball joints as dirt can freely get inside the assembly and cause deterioration of the bearing and stud.

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Useful information on functions, causes of malfunction, diagnosis and replacement intervals

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