| 摘要 |
PROBLEM TO BE SOLVED: To suppress generation of cracks on a bead base surface, enhancing bead durability for overload. SOLUTION: A flat ratio of a bead core is set up as 0.4 to 0.5, an inner diameter Dc of the bead core is made more than a rim diameter Dr, and a difference Dc-Dr is suppressed within a range of 0 to 2.0 mm. An outside surface of the bead part is provided with a first circular arc part of a radius of curvature R1 extending from a tire maximum width point and a second circular arc part of a radius of curvature R2 inscribing in the circular arc part at a contact P and extending up to a heel point. A ratio R1/R2 of the radius curvature is 1.0 to 3.0. A ratio La/Lb of a tire radial direction distance Lb and a tire shaft direction distance La from the heel point to the contact P is 0.55 to 0.75.
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