Master cylinder with shortened dead stroke for a vehicle brake system

The cylinder has a body pierced with a bore in which pistons defining chambers slide. Tight joints with U section are housed in a groove which is arranged in the body, and a supply orifice is arranged in the body. Machining holes (18, 19) communicate a hydraulic liquid tank and the groove to readmit hydraulic liquid in the chambers. An external lip of the joint seals the holes and internal lip seals dilation orifices.