the present application relates to an input torque measuring device for a drive train of a bicycle . the drive train includes a first crank arm and a second crank arm . an inboard end of each crank arm is rotatably mounted to the bicycle at a bottom bracket of the bicycle . at least one chain ring is configured to rotate a driven wheel of the bicycle . a spider is connected to the first crank arm adjacent the bottom bracket and extends out to the at least one chain ring . the spider is configured to transmit force applied to the crank arms directly to the at least one chain ring . the spider may include a plurality of sensors configured to respond to the force applied by the spider to the at least one chain ring . the sensors produce an electronic signal relative to the force transmitted by the spider to the at least one chain ring and a processor configured to receive the electronic signals from each sensor of the spider .