A pneumatic tire having a tread pattern comprising a rib and a block, wherein a rib having the highest rigidity in the circumferential direction of the tire of said at least one rib is offset from the equatorial line of the tire to the shoulder side which is located on the outer side of a vehicle when the tire is mounted on the vehicle and the position of mounting of this rib and the width of the main groove on the shoulder side adjacent to this rib are specified respectively by formulae (I) and (II) described in the specification.