| 摘要 |
<p>To prevent crack occurence at groove bottoms on both side areas of foam rubber tread of all-season studless tires, a pneumatic tire having a tread surface portion (3) composed of at least two outer and inner rubber layers (3A, 3B) is characterized in that the hardness of the inner rubber layer (3B) is from 54 to 80 degrees in Shore hardness and is higher than that of the outer rubber layer, and further the outer rubber layer (3A) is made of foam rubber with a foam rate from 5 to 50% with at least 10% volume ratio with respect to tread volume. The outer foam rubber layer serves to improve tire performance on icy and snowy roads in winter, and the inner ordinary rubber layer serves to reduce change in groove width after vulcanization, that is reduce dynamic strain concentration at lateral grooves and therefore to reduce crack generation at the lateral groove bottoms.</p> |
