Question 1

When the control arm bearing needs replacing

Accepted Answer

The control arm bearing allows arm movement through suspension compression and rebound. The bearing has balls or rollers in a metal casing, which are exposed to water, salt and dust. When it wears, play develops and causes knocks.

Symptoms are the same as a worn bushing — knocks on bumpy roads and imprecise steering. The bearing differs from a bushing in that the bearing permits rotational motion, whereas a bushing only compresses and stretches. On some models (BMW, Audi) the lower control arm is built so that separate bearings can be renewed without full arm replacement.

Question 2

How a control arm bearing is replaced

Accepted Answer

The lower control arm is removed from the car and taken to the workshop. A specialist hydraulic press pushes the old bearing out and the new one in. The work requires the correct formers — a wrong pressing surface damages the bearing or the arm.

After the fitted arm is refitted, the car is reassembled and wheel alignment is done. The expected bearing life is the same as the whole arm — about 100 000–150 000 km.

Question 3

Why does a bearing wear independently of the bushing?

Accepted Answer

The bearing is exposed to constant rotational motion, while a bushing only compresses statically. For that reason the bearing usually wears first even when the bushing is still healthy. Winter driving aggravates the situation because road salt reaches the bearing's contact surface and causes rapid corrosion.

Lower Control Arm Bearing Replacement in Vantaa