A tire comprising: a tread portion for which an intended tire rotational direction (R) is specified, wherein the tread portion comprises block rows composed of blocks circumferentially divided by lateral grooves and arranged circumferentially of the tire , the blocks each have a ground contacting top surface , a first side wall surface located on a heel-side in the intended tire rotational direction (R) of the ground contacting top surface , and a second side wall surface located on a toe-side in the intended tire rotational direction (R) of the ground contacting top surface , the first side wall surface and the second side wall surface are both inclined so that the distance therebetween measured in parallel with the ground contacting top surface becomes decreased toward the radially outside of the tire , and in a cross section of each of the blocks which cross section is parallel with the tire equatorial plane, an angle θ2 with respect to a tire radial direction of the second side wall surface is larger than an angle θ1 with respect to a tire radial direction of the first side wall surface , the angle difference θ2-θ1 between said angle θ2 and said angle θ1 increases toward one side in the tire axial direction, and the block rows include axially outermost shoulder block rows composed of shoulder blocks circumferentially divided by shoulder lateral grooves , and axially inner middle block rows composed of middle blocks circumferentially divided by middle lateral grooves and arranged between the shoulder block rows , characterized in that the groove volume of the shoulder lateral grooves is larger than the groove volume of the middle lateral grooves . a tread portion for which an intended tire rotational direction (R) is specified, wherein the tread portion comprises block rows composed of blocks circumferentially divided by lateral grooves and arranged circumferentially of the tire , the blocks each have a ground contacting top surface , a first side wall surface located on a heel-side in the intended tire rotational direction (R) of the ground contacting top surface , and a second side wall surface located on a toe-side in the intended tire rotational direction (R) of the ground contacting top surface , the first side wall surface and the second side wall surface are both inclined so that the distance therebetween measured in parallel with the ground contacting top surface becomes decreased toward the radially outside of the tire , and in a cross section of each of the blocks which cross section is parallel with the tire equatorial plane, an angle θ2 with respect to a tire radial direction of the second side wall surface is larger than an angle θ1 with respect to a tire radial direction of the first side wall surface , the angle difference θ2-θ1 between said angle θ2 and said angle θ1 increases toward one side in the tire axial direction, and the block rows include axially outermost shoulder block rows composed of shoulder blocks circumferentially divided by shoulder lateral grooves , and axially inner middle block rows composed of middle blocks circumferentially divided by middle lateral grooves and arranged between the shoulder block rows , <EOS>