A system for biomechanical analysis of user posture and automatic customized manufacture of bicycle parts includes a servo-assisted simulator having a handlebar, a saddle, pedal cranks, and actuators, a device detecting input data that includes a 3D scanner for automatically detecting the position of body segments of the user and the angular ranges therebetween and generating three-dimensional physical data units, an electronic platform detecting pressure data of the user, a pair of insoles detecting plantar pressure, a computer connected to the actuators and to the detection device, a memory unit storing optimized initial data and instantaneous data, software comparing the optimized initial data and the instantaneous data and generating final data of the characteristics of the main parts, a spatial representation device spatially representing the final data, and a device for immediate manufacture of the parts using 3D printers. A method of biomechanical analysis and custom manufacture of bicycle parts.