ISO 19940:2017规定了根据ISO 16992，当在瘪胎运行模式下以80 km/h（50 mph）的速度和80 km的距离运行时，能够为车辆提供基本轮胎功能的产品的乘用车轮胎刚度指数测定的试验方法。 该方法旨在确定上述指标，以便通过其空气和结构部件表征预期轮胎的刚度。 为了达到目标，测量不同操作条件下Z方向绝对位置意义上的垂直力和垂直挠度（在零充气压力的情况下近似），并通过本文件中定义的指标进行组合。 此方法不适用于传统轮胎。

ISO 19940:2017 specifies the testing method for determining the tyre stiffness index of passenger car tyres for the products capable of supplying the vehicle with the basic tyre functions, at least, at a speed of 80 km/h (50 mph) and a distance of 80 km when operating in flat tyre running mode, as per ISO 16992. This method is meant to determine the above mentioned index, for the characterization of the expected tyre's stiffness through its air and structural components. To reach the target, the vertical force and the vertical deflection, in the sense of absolute position in Z direction under different operating conditions, are measured (approximated in case of zero inflation pressure) and combined through the metrics defined in this document. This method is not intended to be used for conventional tyres.