Adapting On-vehicle Brake Drag Testing to a Bench Dynamometer 2011-01-2376
Fuel economy can be increased by reducing running resistance or mechanical drag. Since modern disk brake systems produce mechanical drag, a component-level test method was developed to measure and understand this effect.
Measuring brake drag typically requires a vehicle test on a chassis dynamometer, and an engineer must distinguish brake drag from other sources of drag (e.g., tire, wheel bearing, transmission, and others). This method often generates brake drag data that lacks in resolution, accuracy, and repeatability. Alternatively, a new method of measuring drag on a traditional brake dynamometer has been developed that yields statistically relevant and repeatable results.
To accurately measure brake drag on a brake dynamometer, pad temperature, wheel bearing temperature, and caliper experience pressure need to be controlled. Also, depending on the type of wheel bearing used, a correction factor for bearing drag may be needed. Finally, the method by which the brake pads are conditioned, using burnish stops or a specified test mode, and the amount of pad taper wear generated needs to be understood to attain reliable results. With these items in mind, a process was developed to more precisely measure component level drag on a traditional brake dynamometer.