Fuel Economy is one of the most important requirements for modern vehicles. To increase efficiency many factors need consideration. In addition to the engines the entire power train, the tires, and the aerodynamics of the body, the properties of the foundation brakes need to be optimized.

The automotive industry and brake manufacturers have focused on reducing residual drag torque, which is generated between brake rotor and friction linings. This is mainly caused by incorrectly released callipers and /or pads.

In the past, the industry relied on the simple approach that the air gap corresponding to the piston roll-back allows low residual drag torque between pads and disc. However, this is not always the case. Being aware of the phenomena an "Active-Retraction Caliper" (ARC) was developed, which is designed to guarantee a pressure independent constant running clearance. This technique needs to be validated on a suitable test bench as well.

Traditionally, Brake R&D focused on providing a reliable braking performance, low wear, and acceptable low brake noise and vibrations. For managing these tasks a wide range of proven measurement and testing equipment is available. In comparison, the methods for precise determination of residual drag torque are in an early stage. However, in recent years several innovative approaches for the determination of residual drag torque were defined and brought into practical test.

One of these methods is to use a dynamic inertia brake dynamometer combined with a special torque measuring system. This measuring device must be optimized to measure high brake torques, as well as minimal residual drag torques, following realistic test cycles with regard to speed, torque, and energy. The consideration of real brake pressures and energy profiles (dynamometer load collectives) is possible.

Florian Weichert - Mando Corp. Europe GmbH, Hun Kong Young - Mando Corp. Michael Wirtz, Tobias Kurze, Weiss Dieter - Horiba Europe GmbH;