| 摘要 |
PURPOSE: To have equal or more durability to the belt layer tire consisting of more multi-layer steel cord layers and enable lightening by forming a steel cord layer with a specific slant angle against the equator respectively and the widths of respective cord layers for a tread step surface width with a specific value. CONSTITUTION: When respective cord layers of a belt 4 are called by a first- third cord layers 1B-3B from a carcass side, the cords of the cord layers are made so that the cord layers 1B, 2B; 2B, 3B may be arranged crossingly. The slant angles for a tire equator surface E of the cord layers 1B-3B are made in a range of 25-50 deg. for cord layer 1B, 10-20 deg. for 2B, 3B and when the widths of 1B-3B are called by W1 B, W2 B, W3 B, they are W1 B=(0.8 to 0.98)×TW, W2 B=(0.5 to 0.75)×TW, W3 B=(0.5 to 0.75)×TW for the width TW of the step surface 2t of the tread part 2. Therefore, equal or more durability to the tire provided with a belt consisting of four layers cord layer is ensured and lightening can be carried out.
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