Runflat-technology and its impact on design and durability of wheels
State-of-the-art development in the field of tire technology do show a clear trend toward extended-mobility-tires. These tires - also known as runflat tires - have reinforced side walls to guarantee basic mobility properties even in the case of air pressure loss. Since the individual layers as well as the complete build up are different to traditional tire technology, the enhanced layer stiffness generates higher loads to the rim flanges, wheel well and wheel disc. Although these tires seem to be perfectly compatible to conventional wheels with regard to design and mounting process, the stress loading as well as the structural durability of the wheel may be an issue, which has to be examined carefully: Are the design and cross-sectional properties of the wheels appropriate for the complete life cycle of the vehicle? Since automotive wheels are relevant for operational safety, these parts must not fail causing an accident. This has to be ensured by experimental methods such as rig based durability tests. While simplified test procedures such as cornering fatigue tests or radial fatigue tests do not cover the complete load mechanics by the tire, the unique BiAxial Wheel Fatigue Test facilities (ZWARP) were used to generate technical expertise in the field of runflat tires and their relation to the loading of the wheels. Since both loading as well as assembly interaction in the ZWARP are incorporated in a realistic manner, costs and time are saved due to an appropriate accelerated life testing and the elimination of specialized on-road testing.