A mold for molding a tread of rubber mix, this tread comprising a running surface delimited axially by lateral faces, this mold comprising (i) a central part for molding the running surface, movable between an open configuration allowing filling of the mold and a closed configuration allowing molding, the central part comprising at least one rib for molding a groove in the running surface; (ii) two lateral parts for molding the lateral faces, at least one of the lateral parts being axially movable relative to the central part; et (iii) at least one pin for molding a channel inside the tread, this pin being anchored in one of the lateral parts; and in which, when the mold is closed, a contact surface is formed between the pin and the rib, and the pin and/or the rib comprise a buffer made of a deformable material, deformation of which makes it possible to fill in the clearance between the pin and the rib at the contact surface when the mold is closed.