Pneumatic tire

1. A pneumatic tire, comprising:

a tread portion extending in a tire circumferential direction and having an annular shape;

a pair of sidewall portions arranged on both sides of the tread portion; and

a pair of bead portions arranged inward of the pair of sidewall portions in a tire radial direction, wherein

the tread portion comprises:

a plurality of longitudinal grooves extending in the tire circumferential direction;

a plurality of lateral grooves extending in a tire lateral direction; and

a plurality of blocks defined by the plurality of longitudinal grooves and the plurality of lateral grooves,

notch portions are formed in portions of a freely-selected pair of blocks adjacent to each other across a longitudinal groove, the portions facing the longitudinal groove,

the notch portions face with each other across the longitudinal groove,

the notch portion has a notch width and a notch depth larger on a center side in an extension direction of the longitudinal groove than on an outer side in the extension direction of the longitudinal groove,

each of the plurality of blocks has a combined groove formed of a shallow groove and a sipe, the shallow groove having a groove depth of 2 mm or less and extending in the tire lateral direction, the sipe having a groove width of 1.5 mm or less and formed in a groove bottom of the shallow groove,

only the combined groove communicates with the notch portion, and

the sipe in one of the blocks is a branching sipe having at least three end portions in the one of the blocks, at least one of the three end portions terminates within the one of the blocks and another at least one of the at least three end portions opens to one of the lateral grooves at an edge of the one of the blocks.

2. The pneumatic tire according to claim 1 , wherein a portion of the notch portion with the largest notch depth is present at a position of 35% or greater of a maximum groove depth of the longitudinal groove from a groove bottom of the longitudinal groove.

3. The pneumatic tire according to claim 2 , wherein a ratio of an area of the notch portion on a road contact surface of each of the plurality of blocks with respect to a projected area of the road contact surface of each of the plurality of blocks falls within a range from 3% to 16%.

4. The pneumatic tire according to claim 3 , wherein the notch length of the notch portion falls within a range from 40% to 75% of a tire circumferential direction length of the block provided with the notch portion.

5. The pneumatic tire according to claim 4 , wherein the notch portion has a bottom portion formed of a surface parallel with the road contact surface of each of the plurality of blocks.

6. The pneumatic tire according to claim 1 , wherein a ratio of an area of the notch portion on a road contact surface of each of the plurality of blocks with respect to a projected area of the road contact surface of each of the plurality of blocks falls within a range from 3% to 16%.

7. The pneumatic tire according to claim 1 , wherein the notch length of the notch portion falls within a range from 40% to 75% of a tire circumferential direction length of the block provided with the notch portion.

8. The pneumatic tire according to claim 1 , wherein the notch portion has a bottom portion formed of a surface parallel with the road contact surface of each of the plurality of blocks.

9. The pneumatic tire according to claim 1 , wherein each of the longitudinal grooves between tread edges of the tread portion are inclined with respect to the tire circumferential direction.