In a rotor system, in particular for a bicycle (1), on which a frame (3) bears a fork (8) for the front wheel (10), and a handle bar (18) is connected to the fork (8) by means of a handle stem (14) on a fork shaft (12) of the fork (8), with a first line (52), for a fluid, associated with the handle bar (14), with a second line (55), for a fluid, associated with the frame (3), and a rotor that contains two components (14, 41) that can rotate relative to each other without limits and that, by intimate contact against each other, create a closed fluid connection between the first line (52) attached to one component (14) and the second line (55) attached to the second component (41) in order to transmit the actuation of an actuation mechanism (50) associated with the handle bar (18), the handle stem (14) is one of the two components (14, 41) that can rotate relative to each other without limits and contains at least one chamber (30) included in the fluid connection between the two lines (52, 55).