Abstract: A pseudo crank rotational speed determining unit for a bicycle includes a speed determining unit which determines a speed of the bicycle and a pseudo crank rotational speed determining unit. The pseudo crank rotational speed determining unit operatively communicates with the speed determining unit and determines a pseudo crank rotational speed from the determined speed of the bicycle. In a more specific embodiment, a front gear identifying unit identifies a front gear of the bicycle, and a rear gear identifying unit identifies a rear gear of the bicycle. The pseudo crank rotational speed determining unit determines a gear ratio from the identified front gear and the identified rear gear, and then the pseudo crank rotational speed is determined from the determined speed of the bicycle and from the determined gear ratio.

Abstract: An expandable bearing retainer includes a retainer body for supporting a plurality of balls, and an expanding mechanism for allowing the bearing body to elastically expand in the circumferential direction so as to increase the inner diameter of the retainer. In a more specific embodiment, the retainer body includes a plurality of circumferentially disposed rolling element retaining openings formed on a first side of the retainer body. A plurality of slits are formed on the an opposite second side of the retainer body for forming the expanding mechanism. Each of the plurality of slits may be disposed between an adjacent pair of the plurality of rolling element retaining holes so as to form an undulating overall shape for the retainer.