Difference Between Wheel Bearings & Ball Jointsby Sam Grover
Wheel bearings and ball joints are both parts of cars. The wheel bearing is the component in the middle of the wheel around which the wheel turns as the car moves, while the ball joint is the connection between the wheel and the suspension.
Wheel bearings are circular pieces of equipment. They are designed to minimize metal-to-metal contact from the wheel turning. Without wheel bearings, the wheel would be rubbing directly against the suspension as the car drives. This constant wear and tear would affect both of these expensive pieces of equipment. A wheel bearing essentially takes on the damage from these more complex components; by wearing a wheel bearing down over time, you are saving yourself the costly maintenance of a worn-out wheel or suspension.
Ball joints are similar to your elbow. They have a ball enclosed in an arm, which allows the arm to swivel freely without the ball falling out. The purpose of these is to transfer force from the suspension to the wheels; as you turn the steering wheel, the ball joint moves with the suspension, which turns the wheel it is attached to and lets you turn the car.
There are a wide variety of differences between these pieces of equipment. For one, a ball joint is designed to transfer force, while a wheel bearing is designed to absorb force. Their basic shape is also profoundly different -- the ball joint is a couple of pieces put together in a specific way, while a wheel bearing is just a ring-shaped piece of metal. Most important, though, is their underlying function. The wheel bearings are designed to keep the car moving forward. The ball joints, on the other hand, are designed to give the driver control over its direction.