JPS595421B

A mold cavity for producing a pneumatic vehicular tire is radially expandable to form successive coaxial annular layers, e.g. carcass, reinforcing belt and tread, of the tire body. The mold cavity is defined by a stationary core, several outer annular mold walls alternately juxtaposable with the core, and a pair of opposite cheeks axially bracketing the core and the juxtaposed segments. The segments of each mold wall are movably mounted on a respective carrier ring and are radially outwardly retractable thereon to clear the cheeks whereby they can be axially moved into and out of alignment with the core. With successive operative positioning of segment sets of progressively increasing inner radii around the core, the mold cavity is expanded after each molding step preparatorily to formation of the next layer after partial hardening of the elastomeric material of the layer previously formed therein.