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Control Arm Bushing

Wheels have to travel up and down as a vehicle is driven. This means a spring, shock absorber, and control arms must be added to each wheel position to allow the travel to remain consistent, predictable, and comfortable.

If the control arms were bolted directly to the vehicle frame, i.e. metal-on-metal, the control arm and frame would wear quickly, and the vehicle would pop and grind on every movement. This is why control arm bushings are used.

 

Control arm bushings are wearable components that separate the frame from the control arm, providing not only a cushion, but a tough barrier against metallic contact. They are composed of a metal sleeve surrounded by a composite rubber or polyurethane padding (insulator) that is pressed into the control arm. Typically, a large bolt or pin goes through the center of the bushing to secure the control arm to the subframe.The bolt or pin is protected from wear by lubrication and appropriate sizing.

Symptoms of Wear or Failure of the Control Arm Bushing

  • Suspension may make noises like grinding, squeaking or knocking when going over bumps and turning. This is because the rubber or polyurethane insulator has broken down, and there is now room for the control arm to bounce back and forth, contacting the metal sleeve inside the bushing.
  • When there is room for the control arm to move side-to-side, the tire moves with it, so the vehicle will wander from side to side while driving, even if you hold the steering wheel in one position.

  • Again, if the control arm bushing allows the control arm to move, especially the upper control arm, the tire will show atypical wear patterns, alerting you or your technician that the alignment is now incorrect. This can degrade a tire very rapidly, even when the tire is new. Typically the tire will wear along one or both edges, depending on which control arm bushing(s) have failed.

  • The steering wheel will also move from the centered position when traveling in a straight line. This, again, is due to alignment changes resulting from the failed bushing(s).

Related Repair Advice on the Control Arm Bushing

  • If possible, we recommend replacing control arm bushings as a set, especially on vehicles subject to heavy usage. The logic behind the idea is that the parts are identical when new, and they both endure nearly the same operating conditions, so failure of the others are likely when one has failed.
  • In some cases, the control arm must be replaced in order to replace the bushings, however, the majority of control arm bushings can be pressed in by a hydraulic press, or a specialized control arm bushing installation and removal tool.
  • Replacing the control arm bushings will likely affect the alignment settings. We recommend a four-wheel alignment when the control arm bushings, or any suspension components are replaced

Performance polyurethane or hard rubber control arm bushings are available for purchase, and make greatly improve handling characteristics of any vehicle. Before purchasing or installing performance oriented bushings, it is important to research and understand the drawbacks of moving away from the OEM-style bushings. Performance bushings can squeak when they are brand new, and vibrations will travel from the road. These factors reduce interior comfort, increase interior vibrations, and cause excess road noise. 

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