Ball Joints

Ball joints, which connect the suspension control arms to the steering knuckles with a spinning, spherical stud and a socket, operate as hinges and allow the wheels to move widely, allowing for both side-to-side steering and up-and-down bump absorption. Depending on the suspension configuration, some vehicles have upper and lower front ball joints, and either one may serve as the load-bearing joint that supports the weight of the vehicle (load-bearing joints tend to wear out sooner). Only the lower ball joints, and sometimes the rear ball joints, are present in automobiles with McPherson strut suspensions. Although "greasing" ball joints used to be a standard element of oil changes, most automobiles come with sealed ball joints that don't require routine lubrication.