than 100 kg mm 2 the growth of crack in the cord during the running becomes large and the effect of improving the bes resistance is not obtained in the steel cord according to the invention it is required that the breaking load s satisfies a relationship represented by the following equation because the sufficient internal pressure is first held when the above relationship is satisfied when the steel cord is applied to tires for truck and bus used on bad road under heavy load it is preferable to satisfy the following relationship the above breaking load s of the cord is obtained by drawing high carbon steel having a c content of 0 80 0 90 by weight while the reduction ratio is controlled to a proper value of not less than 94 according to the invention it is required that the steel cords are arranged so that a distance g between the adjoining cords is within a range of 0 6 2 0 mm in the belt layer g is measured from the edge of one cord to the adjacent edge of the next cord when g is less than 0 6 mm cracks produced around adjoining cords are apt to be connected to each other and bes is easy to be caused while when g exceeds 2 0 mm the rigidity of the belt decreases to degrade the steering property of the tire and the wear.