A method and apparatus for controlling the preload of duplex rolling element bearings systems under various temperatures is described. A spacer or a plurality of spacers may be located adjacent to the rings of the duplex rolling element bearings. The spacer or spacers may be heated or cooled to increase or decrease the axial dimension of the spacer or spacers. Changing the axial dimension of the spacers changes the preload of the duplex rolling element bearing system. The preload of the system may be estimated by receiving an input from a sensor or sensors located on the duplex rolling element bearings system. The sensor may be a temperature sensor or a force transducer.