This part of ISO 4666 specifies a constant-stress flexometer test for the determination of the temperature rise and resistance to fatigue of vulcanized rubbers. Many rubber products, such as tyres and belts, are tested by subjecting them to an oscillating load with a constant peak stress amplitude. In order to obtain good correlation between accelerated tests and in-service exposure of these products, this part of ISO 4666 gives instructions for carrying out measurements under such conditions. This method is not recommended for rubber having a hardness greater than 85 IRHD.