Reinforcing structure for bead portion of radial tire for heavy load

A radial tire for heavy loads comprising:

• a pair of bead parts each provided with a bead core and having a bead base part surrounding the bead core, the bead base part having a bead base radially inward of the bead core;
• a carcass extending between the beads and having a ply of metallic cords laid at an angle of 90 to 60 degrees to the equatorial plane of the tire, the ends thereof turned up around the bead cords from the axially inside to outside thereof to form a carcass main part on the inside of the bead core and a carcass turned up part on the outside of the bead core extending radially outwardly;
• a pair of sidewalls on the carcass extending to the bead part;
• a metallic cord reinforcing layer having a ply of metallic cords and turned up around the bead core to form an outside part extending radially outwardly along the axially outside of the carcass turned up part and an inside part extending radially outwardly along the axially inside of the carcass main part;
• an outside reinforcing layer having a ply of organic fiber cords and disposed axially outside from a point (h10) in the bead base part to a point (h3) beyond both the radially outer end of the metallic cord reinforcing layer and the radially outer end of the carcass turned up part;
• an inside reinforcing layer having a ply of organic fiber cords and disposed on the axially inside of the carcass main part, the inside reinforcing layer extending from a point (h'3) radially outward of the radially outer end of the inside part of the metallic reinforcing layer to a point (h5) in the bead base part so as to be interposed between the carcass main part and the inside part of the metallic cord reinforcing layer;
• a bead apex disposed between the carcass main part and the carcass turned up part and extending radially outwardly and decreasing in thickness from the bead core to a point (h9) beyond the radially outer end of the outside reinforcing layer;
• a rubber chafer made of a hard rubber having a modulus of elasticity of 50 to 60 kgf/sq.cm at 100% elongation and a JIS (A) hardness of 75 to 85 and disposed outside the outside reinforcing layer, the rubber chafer extending radially outwardly from the bead base part, the radially outer part thereof gradually decreased in thickness toward the end thereof;
• an inner sidewall made of a soft rubber having a modulus of elasticity of 15 to 25 kgf/sq.cm at 100% elongation and a JIS (A) hardness of 55 to 65 and disposed between the outside reinforcing layer and the rubber chafer,
• the inner sidewall extending radially inwardly to a point in the bead base part beyond the radially inner end of the outside reinforcing layer and further extending radially outwardly to a point (h7) beyond the radially outer end of the outside reinforcing layer so as to contact with the bead apex;
• and
• the radially outer part of the rubber chafer and the radially outer part of the inner sidewall being interposed between the bead apex and the sidewall.