The effect of modulus of tire cords in stabilizer and body plies on the performance of a radial automobile tire is discussed. Cord modulus was varied systematically by using polyester, rayon, and aramid materials. High speed, endurance, and plunger energy were not effected. Rolling resistance was higher with aramid cord than with polyester cord in the body ply, but there was no effect of cord material in stabilizer plies. Increase of cord modulus in the stabilizer ply, however, did produce significantly higher cornering coefficient. Wear resistance was also higher, especially under high severity test conditions.