A mold for vulcanizing an unvulcanized tire blank comprises: two axial members each carrying a molding surface for molding a sidewall of the tire, at least one of the axial members being movable between a position for molding the sidewall and a position for unmolding the tire; at least one molding member for molding a channel in a tread of the tire, the molding member being movable between a channel-molding position and a channel-unmolding position; and axial movement means for axially moving the channel-molding member between its molding and unmolding positions. The axial movement means include releasable connection means between the channel-molding member and the axial member.