Tread of heavy duty pneumatic radial tire

摘要

A tread of a heavy-duty pneumatic radial tire comprises a pair of upper and lower rubber layers having mutually different moduli of elasticity and a small-width groove formed in the upper rubber layer in such manner as to be substantially continuous in a circumferential direction of the tire. The dimension between a boundary surface bordering the two rubber layers and a bottom of the groove is set to be 1 mm or more. Accordingly, the arrangement prevents the occurrence of cracks due to a deforming stress acting in the groove bottom occurring when the tire rolls or rides on a curbstone.