A casting or injection mold for vehicle tires comprises two separable half-shells together defining an annular cavity into which a segmented core is introduced, radially inwardly converging core segments alternating with parallel-sided or radially inwardly diverging core segments to facilitate extraction of the core from the molded tire. In operation, one or more of the non-converging segments are immobilized within the mold, with the aid of mating formations on these segments and on the two half-shells, while the converging segments are urged radially inwardly by resilient or fluidic forces. In a specific embodiment these forces are supplied by a contractile annular spring with projections received in axially extending undercuts of all the segments.