Ball joints are made up of a lower ball joint and upper floating king-pin. The upper ball joint is designed as a pivot point determining the axis on which the knuckle will move and thus, only sees a lateral load. The lower ball joint tracks the knuckle on an imperfect axis, the spherical lower is required to allow the knuckle to move freely with only a slight vertical travel through its steering cycle. Carli Extreme-Duty Upper Ball Joints have a pin and housing but the “hat” of the pin contacts the housing. This adds a second wear surface to further distribute the load applied laterally to the ball joint while providing the same failsafe as a factory ball joint ensuring the pin cannot be pulled through the bottom of the ball joint housing. Further, there is no sleeve isolating the wear surfaces, eliminating the point of failure. A Viton Seal at the bottom of the housing prevents the environment elements from entering the ball joint. The lower joints have no liners of any kind. At the top, a bronze wear surface preloaded by a disc spring, safety washer and snap ring ensures the ball joints wear surfaces are always held tightly together for superior performance. Materials and process play an important role in the impressive durability and performance of Carli Extreme-Duty Ball Joints. It starts with masking. All surfaces but the wear surface are masked with a copper plating. Once plated, the ball joints head to carburizing. The carburizing creates an extremely hard surface with a case-hardness (penetrating depth) of 20-25 thousandths. When the ball joint has completed the carburizing/heat treatment, it’s stripped of the copper masking, leaving the entire joint heat treated and the wear surfaces incredibly hard. The entire joint is then covered with a corrosion resistant gray coating for protection from the elements.