Method for producing a tire comprising an improved tread with a foamed material

A process for manufacturing a tire in which an uncured blank of the tire is vulcanized in a mold,

• this tire comprising a layer of cellular material that forms a running layer of a tread of the tire in which hollow tread pattern elements are made,
• the running layer having
• a thickness E, and
• a degree of expansion of greater than or equal to 50%,
• wherein:
• the uncured blank is provided with a mass of material, comprising p,p′-oxybis(benzenesulphonyl hydrazide) that forms a pore-forming agent, this material comprising the pore-forming agent being intended to form the cellular material,
• the uncured blank is placed in a vulcanization mold comprising molding elements for molding the hollow tread pattern elements,
• the mold being such that at least 95% of the molding elements each satisfy the following two conditions a) and b):
• a) the molding element is separated from at least one other molding element by a separation distance, expressed in millimetres, of less than or equal to
• DM=6.85+0.0065 T3,
• T being the amount of p,p′-oxybis(benzenesulphonyl hydrazide) in the mass of material intended to form the cellular material, and T being greater than or equal to 3 phr,
• the separation distance between two molding elements being the shortest distance between these two molding elements travelled between these molding elements,
• b) the molding element is intended to form a hollow tread pattern element having a depth at least equal to 80% of the thickness E of the running layer.