| 摘要 |
The object of the present invention is to provide a pneumatic radial tire for heavy load which effectively improve three kinds of durability, i.e., durability of the turn-up portion of the carcass, durability of the rubber layer of the carcass and cut resistance of the carcass cords. A steel radial carcass 12 is composed of main carcass portion 12M and turn-up portions 12E. The tire is fitted on a standard rim 20 and suppose that P1 is a position on the tire outer surface with a radial distance of (R+1.18*Hf) from the central axis of the tire, P2 is a position on the tire outer surface with a radial distance of (R+0.81*Hf) from the central axis of the tire, T1 and T2 are intersections of normal lines drawn from P1 and P2, respectively, to the main carcass portion 12M and the turn-up portion 12E, M1 and M2 are intersections of the normal lines and the main carcass portion 12M. T1, T2, M1 and M2 satisfy given mutual positional relationships.
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