a processable rubber stock is produced by the preparation of a silica - filled , vulcanized elastomeric compound comprising mixing an elastomer with an amorphous silica filler , from 0 to less than about 1 % by weight based on said silica filter of bispropyl ] tetrasulfide , an alkylalkoxysilane and a cure agent . a further processing aid comprising at least one of an ester of a fatty acid or an ester of a polyol is preferred . the elastomer is preferably a diene monomer homopolymer or a copolymer of at least one diene and at least one monovinyl aromatic monomer . by effecting vulcanization , a vulcanized elastomeric compound is produced containing good physical properties for use as tread stock for a pneumatic tire .