Patent ID: 8272414

Claim:
A pneumatic tire, comprising: sidewalls on both tire-width-direction edges of the tire; and a tread that is located radially outward of the sidewalls, includes a cap tread, and has a surface serving as a tread surface formed of a plurality of arcs of different curvature radii, as seen in a meridional cross section thereof, wherein provided that the pneumatic tire is mounted on a normal rim and internal inflation pressure is 5% of normal internal pressure, and that the tread surface is formed of: a center arc located in a center portion in a tire width direction; a shoulder-side arc located at least on a vehicle-outer side in the tire width direction relative to the center arc; and a shoulder arc contouring a shoulder located on an edge of the tread surface, at least on the vehicle-outer side in the tire width direction, F1, given by Formula (1) below expressing a relation between an outline range L1 and an extended tread width TDW, falls in a range of 0.64≦F1≦0.7, F2, given by Formula (2) below expressing a ratio of a curvature radius TR1 of the center arc to a tire outside diameter OD, falls in a range of 1.2≦F2≦2.0, F3, given by Formula (3) below expressing a ratio of a curvature radius TR2 of the shoulder-side arc to the curvature radius TR1 of the center arc, falls in a range of 0.1≦F3≦0.2, and F4, given by Formula (4) below expressing a relation among an aspect ratio β, the extended tread width TDW, and a total width SW, falls in a range of 0.35≦F4≦0.48: F 1 =L 1/( TDW× 0.5) (1) F 2 =TR 1 /OD (2) F 3 =TR 2 /TR 1 (3) F 4=(β× TDW )/(100× SW ) (4) where TR1 is the curvature radius of the center arc, TR2 is the curvature radius of the shoulder-side arc, L1 is the outline range of a width from an equatorial plane to a lateral edge of the center arc, TDW is the extended tread width being a lateral width of the tread surface, SW is the total width being a lateral width between laterally outermost portions of the sidewalls that are located on the both tire-width-direction edges and face each other, OD is the tire outside diameter being a largest diameter of the tread surface in a tire diameter direction, and β is the aspect ratio, wherein at least a portion of the cap tread is made of a compound having 300% tensile modulus of 5 MPa to 10 MPa.