PURPOSE: To improve stability, controllability and durability at high speed by establishing the predetermined relationship between a tread grounding method under the predetermined load and a size for grounding from the outer end of a main groove to the grounding end thereof, and applying the predetermined shape to the periphery of a shoulder section under no load.

CONSTITUTION: A tire is assembled into a standard rim. In this case, a distance between the grounding ends P2 of a tread T is taken at L, when the tire is charged with the predetermined pneumatic pressure and applied with the predetermined load. In addition, when a grounding size between the point P2 and the outer end P1 of a main groove 10 or 12 is (a), the value of (a)/L is between 0.15 and 0.25. Also, when a maximum distance from the periphery of a shoulder section TA to a segment between the points P1 and P2 is (t) under the predetermined pneumatic pressure and no load, the value of (t) is taken as 0mm≤(t)≤0.5 mm. According to this construction, stability, controllability and high-speed durability on both dry and wet roads can be improved.