Abstract: An arrangement for mounting two bearings supporting a shaft within a housing, each bearing having an inner race secured to the shaft and an outer race, the arrangement comprising two annular membrane-shaped spacer members having a high radial stiffness and a predetermined axial flexibility, the spacer members having an outer edge and an inner edge, the inner edge of each spacer member being secured to the outer race of a respective bearing and the outer edge of each spacer member being secured within the housing, both spacer members being subjected to a predetermined amount of axial deformation with respect to their unstressed condition, whereby the spacer members exert a precisely determined axial preload onto said outer races of the bearings.