Bicycle hydraulic disc braking system and a method and system for diagnosing the braking system

A method for diagnosing a bicycle hydraulic disc braking system, the method comprising the steps of:

• a) providing a master cylinder assembly comprising a cylinder, with a piston that reciprocates inside the cylinder against the action of a return spring, and a hydraulic tank having a bottom, a ceiling, and a membrane that divides the tank into a variable volume filled chamber and a complementarily variable volume empty chamber, said hydraulic tank being fluidically connected to the cylinder through at least one main passage in said bottom,
• b) providing a metering device for measuring a distance of the membrane from the ceiling of the hydraulic tank,
• c) inserting a hydraulic fluid in the master cylinder assembly,
• d) reciprocating the piston inside the cylinder,
• e) evaluating whether an output signal of the metering device is indicative of a temporary approach of the membrane to the ceiling having an extent corresponding to a predetermined approach range, and,
• f) establishing that the master cylinder assembly is correctly operating when the output signal is indicative of a temporary approach of the membrane to the ceiling.