Pneumatic tire

A pneumatic tire comprising:

• a pair of bead portions each with a bead core embedded therein, and
• a carcass extending between the bead portions through a tread portion and sidewall portions,
• the carcass comprising a carcass ply extending between the bead portions and turned up around the bead core in each bead portion from the axially inside to the axially outside so as to form a pair of turnup portions extending radially outwardly, and a main portion therebetween, wherein
• each of the bead portions is provided with a reinforcing rubber portion disposed adjacently to an axially outer side of the turnup portion,
• the reinforcing rubber portion is composed of an axially inner rubber layer, and an axially outer rubber layer,
• wherein
• a loss tangent δ2 of the axially outer rubber layer is 0.07 or more and 0.20 or less,
• a loss tangent δ1 of the axially inner rubber layer is not less than 50% and not more than 70% of the loss tangent δ2 of the axially outer rubber layer,
• a complex elastic modulus E*2 of the axially outer rubber layer is 40 MPa or more and 150 MPa or less,
• the complex elastic modulus E*2 of the axially outer rubber layer is not less than 120% and not more than 200% of a complex elastic modulus E*1 of the axially inner rubber layer,
• wherein
• the axially inner rubber layer is composed of
• a radially outer reduced-thickness portion whose thickness decreases toward a radially outer end of the axially inner rubber layer,
• a radially inner reduced-thickness portion whose thickness decreases toward a radially inner end of the axially inner rubber layer, and
• a constant-thickness portion therebetween having a constant thickness, and
• a length Lc of each of the radially outer and radially inner reduced-thickness portions is not more than 5 mm,
• wherein
• the axially outer rubber layer is composed of
• a radially outer reduced-thickness portion whose thickness decreases toward a radially outer end of the axially outer rubber layer,
• a radially inner reduced-thickness portion whose thickness decreases toward a radially inner end of the axially outer rubber layer, and
• a constant-thickness portion therebetween having a constant thickness, and
• a length Lc of each of the radially outer and radially inner reduced-thickness portions is not more than 5 mm,
• wherein
• the radially outer end of the axially outer rubber layer is positioned radially outside the radially outer end of the axially inner rubber layer, and
• the radially inner end of the axially outer rubber layer is positioned radially inside the radially inner end of the axially inner rubber layer, and
• the axially inner rubber layer and the axially outer rubber layer are in contact with each other from the radially outer end of the axially inner rubber layer to the radially inner end of the axially inner rubber layer,
• wherein
• an axially inner surface of the reinforcing rubber portion from its radially outer end to radially inner end is directly adjacent to the carcass ply turnup portion,
• an axially outer surface of the reinforcing rubber portion from its radially outer end to radially inner end is directly adjacent to a sidewall rubber forming the outer surface of the tire in the sidewall portion and a clinch rubber forming the outer surface of the tire in the bead portion,
• wherein
• a complex elastic modulus E* of the sidewall rubber and a complex elastic modulus E* of the clinch rubber are smaller than the complex elastic modulus E*1 of the axially inner rubber layer;
• and
• wherein the loss tangents and the complex elastic moduli are measured under the following conditions in accordance with the provisions of JIS-K6394:
• initial strain:
• 10%
• dynamic strain amplitude:
• +/−2%
• frequency:
• 10 Hz
• deformation mode:
• stretch
• measurement temperature:
• 70° C.