Ball joint

Disclosed is a ball joint with a ceramic inner race 20 and an outer race with width L. The inner race has a longitudinal axis A1 and two convex lateral portions 25, 26 extending from a central portion 24.The radial distance Y between the lateral portions and the longitudinal axis when free from load is defined by the equation Y = R - K · ln[1-(2X/L)2], where K is a predetermined constant, such as between 0.001 and 0.5, X is the axial distance measured from the connection point of the of the relevant lateral portion to the central portion, and R is the radius of the central portion. The maximum value for Y is achieved when X=L/2, i.e. at the junction between the lateral portions and lateral faces 23. The description highlights that Y increases continuously from the relevant connection point to the corresponding lateral face junction and that the radial distance at the junction may be between 10 microns and 1 millimetre greater than the radius R. The outer race may also be ceramic. A sleeve or bearing may be installed in the bore of the inner race.