DIAGNOSIS SYSTEM AND METHOD FOR A BICYCLE HYDRAULIC BRAKING SYSTEM OF A DISC TYPE

One aspect of the invention relates to a diagnosis method for a bicycle hydraulic braking system (1) of the disc type, in particular of a master cylinder assembly (7) thereof, which comprises:a) providing a master cylinder assembly (7) comprising a cylinder (8), a piston (9) movable by reciprocating motion inside the cylinder (8) against the action of a return spring (10), as well as a hydraulic tank (20) comprising a bottom (23), a ceiling (22), and a membrane (25) dividing the tank (20) in a variable volume filled chamber (26) and a complementarily variable volume empty chamber (27), said tank (20) being fluidically connected to the cylinder (8) through at least one main passage (21) in said bottom (23),b) providing a meter device (40) of the distance of the membrane (25) from the ceiling (22) of the tank (20),c) inserting a hydraulic fluid (5) in the master cylinder assembly (7),d) moving the piston (9) by reciprocating motion inside the cylinder (8),e) evaluating, with processing means, whether an output signal of the membrane detector device (40) is indicative of a temporary approach of the membrane (25) to the ceiling (22) having an extent corresponding to a predetermined approach range,f) establishing that the master cylinder assembly (7) is correctly operating if the evaluation is positive, that the master cylinder assembly (7) is not correctly operative if the evaluation is negative.Another aspect of the invention relates to a diagnosis system of a bicycle hydraulic braking system.