A bicycle has a spider including a torque input section and at least one torque output section; a crank assembly coupled with the spider through the torque input section and applying an input torque to the spider; a chainring mounted to the spider through the at least one torque output section and receiving an output torque from the spider; a gauge disposed and oriented generally along a tangential direction or a quasi-tangential direction with respect to the torque input section and the at least one torque output section; and a circuitry coupled to the gauge and receiving a signal from the gauge.