| 摘要 |
PROBLEM TO BE SOLVED: To enhance the belt durability under severe service conditions to run with a high load and high speed for a long time. SOLUTION: A tread rubber layer 6 is embodied in a double structure consisting of an under-tread rubber layer 7 having a low hardness and a cap tread rubber layer 8 having a higher hardness, and a cushion rubber layer 4 is interposed between the edge parts 3b and 3c of the second 3B and third belt layers 3C, and an edge cover layer 5 is installed on the periphery of the edge part 3c of the third belt layer 3C. In this radial tire for heavy duty, a large thickness is given to the under-tread rubber layer 7 in the neighbourhood of the edge (e) of the second belt layer 3B having the maximum belt width, and the thickness (t) of the under-tread rubber layer 7 from the edge (e) on the perpendicular K drawn from the edge (e) to the buttress part surface B1 is made over 0.6A compared with the distance A between the edge (e) and the buttress part surface B1.
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