A valve for balancing the braking system of a vehicle equipped with two separated master cylinders for the independent braking of the wheels situated at the two sides of the vehicle, includes two ring packings which cooperate with the intake of a transfer channel connecting both master cylinders, wherein at least one of the packings of the balancing valve is housed within a containment space suitable for allowing, in elastic conditions, a displacement of this packing that increases in noticeable manner the volume of the space which is located on the packing side communicating with the transfer channel. This packing may have a substantially usual shape, and the possibility of its displacement as a consequence of an elastic deformation of the packing may be entrusted entirely to the shape of the containment space, or a special shape of the packing itself. An elastic member brings the packing to its normal configuration when the cause of its displacement ceases.