The original bushing is made of rubber: it filters out vibrations well, but it deforms under load. When cornering or braking, the arm moves by a few millimetres and the wheel alignment changes during the manoeuvre - this is the vagueness between the steering wheel and the wheels.

Polyurethane deforms much less: the connection becomes precise and repeatable, and the car responds at the same point every time. In return, more road noise and vibrations may be felt in the cabin, especially when cold.