Bushings are cushions made of rubber, polyurethane (often shortened to “poly” or (“urethane”) or other materials. They’re mounted on car suspension and steering joints to absorb road bumps, control the amount of movement in the joints and reduce noise and vibration.
The kingpin (also king-pin, king pin and k pin) is the main pivot in the steering mechanism of a car or other vehicle. The term is also used to refer to part of a fifth wheel coupling apparatus for a semi and its trailer or other load.