What Are Upper and Lower Ball Joints?


Quick Answer

Upper and lower ball joints are components that are found in almost every automobile. They are spherical bearings that connect the control arms to the steering knuckles in the front two wheels of the automobile. The ball joints work similarly to the joint of the human hip. The upper ball joints are located at the top of the suspension system, while the lower ball joints are located on the bottom, just as their names suggest.

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Full Answer

There are two pieces that make up every ball joint: the bearing stud and the socket. The bearing stud is essentially a ball bearing on a stick. The ball end of the bearing stud fits into the socket, and the other end is tapered and threaded so that it can be fit into a hole on the steering knuckle.

The bearing stud and socket are both made out of steel. A rubber fitting covers the gap where the bearing stud enters the socket so that dirt, dust and other materials that may impede the smooth movement of the joint don't get stuck in the component. Occasionally, this does happen and the ball joint may need to be replaced.

Ball joints are very important in the steering and suspension of a car. They, along with the control arms, enable movement in all three planes, which allows a driver to steer the car and the suspension to make the ride more comfortable and enjoyable.

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