This paper is aimed to propose the practical method of estimation of the critical speed of the standing-wave phenomenon of tyre, although it is necessary to measure the fundamental physical quantities in advance by comparatively simple testings. It is explained that the square of the wave velocity of the tyre is the square sum of the velocity due to the stiffness tyre, of the velocity due to the internal pressure, and the velocity due to the centrifugal force of the rotating tyre. In addition, the amount of the reduction of the stiffness of the tyre due to the temperature rise in the rolling tyre is estimated. The practical empirical method is also proposed to take this reduction of the stiffness into account for the practical estimation of the critical speed.