A wireless control system for a bicycle, comprising a first shift control unit for a component of a bicycle, the first control unit comprising a radio configured to receive control signals, wirelessly transmitted by a second control unit of the bicycle; the radio operable to receive the control signals only when the radio is operating in a listen mode; and a processor configured to: activate the listen mode of the radio for a first length of time; detect, with the radio, a noise level during the first length of time; and extend the activation of the listen mode for a first extended time period when the noise level achieves a noise level threshold.