This part of ISO 4666 specifies a rotary flexometer test for the determination of the temperature rise and resistance to fatigue of vulcanized rubbers under rotary shear loading. It allows the use of all four types of test conditions described in ISO 4666-1. It gives directions for carrying out measurements which make possible predictions regarding the durability of rubbers in finished articles (tyres, bearings, supports, V-belts, cable pulley insert rings and similar products subject to dynamic flexing in service). However, owing to the wide variations in service conditions, no simple correlation between the accelerated tests described in this part of ISO 4666 and service performance can be assumed.