A forged or cast piece of metal that an automobile wheel mounts to. Wheel bearing assemblies typically fit inside the center of the wheel hub to allow free rotation around an axle shaft or spindle. Bearing assemblies that mount inside a wheel hub are often called wheel hub bearing assemblies. Depending on the vehicle manufacturer, some wheel hub bearing assemblies are constructed with integral bearing assemblies that cannot be replaced separately. Instead, the wheel hub must be replaced as a whole. more details on