Ball joint

Disclosed is a ball joint with an inner race 20 and a ceramic outer race 30. The outer race has a width L and a longitudinal axis A1. The radial clearance Y between the races when free from load is defined by the equation Y = -K · ln[1-(2X/L)2], where K is a predetermined constant, such as between 0.001 and 0.5, and X is the axial distance measured from a mid-plane P of the outer race that is perpendicular to the longitudinal axis. The maximum value for Y is achieved when X=L/2, i.e. at the junction between outer race surface 32 and lateral faces 33. The description highlights that Y increases continuously from the mid-plane P toward the junction and that the radial clearance at the junction may be between 10 microns and 1 millimetre. A self-lubricating fabric may be interposed between the races, and may specifically be fastened to the outer race. The inner race may also be ceramic. Such continuously increasing radial clearance on the outer race avoids edge stress concentration on the junction when the shaft bends.