Control arm bushing
Definition
Control arm bushings are rubber (or rubber-and-fluid hydraulic) sleeves bonded between an inner steel tube and an outer shell that let the arm pivot while isolating road noise and controlling how the wheel moves under braking and cornering loads. The rear bushing of a front lower arm on many cars is hydraulic to absorb harshness, and it is the most common failure: the rubber cracks, the fluid leaks and the arm can move several millimetres fore-and-aft. Symptoms are a clunk or knock when braking or shifting from drive to reverse, steering wheel shake under braking that is often misdiagnosed as disc runout, a vague or wandering steering feel, and tyres wearing on one edge because caster and toe change with every input. Inspect for cracked, torn or oil-soaked rubber, a bushing that has walked out of its housing, and movement when levering the arm; hydraulic ones show a wet patch where the fluid escaped. Bushings are pressed in and often sold only with a new arm; replace in pairs and align afterwards. No codes; related complaints are brake judder with good discs, clunks, pulling and poor straight-line stability.