Influence of Friction Material and Brake System Strain on Pedal Feeling for Racing Vehicles

Pedal feeling for race cars is a subject of great uncertainties, due to singularities of this type of system and the large amount of components that may influence it. High performance friction materials are developed considering different requirements, aiming to establish a commitment relationship, among different characteristics - for example, compressibility, friction and wear - for critical conditions of use, such as high temperatures and pressure applications. The purpose of this study is to analyze the brake system strain through the fluid displacement measurements and analysis, during brake events, applying different brake pressures for static tests performed on an inertial dynamometer. Test procedures applied aim to simulate automobile race laps, according measurements previously done. Two high performance friction materials, specifically developed for this application, with similar compositions - around 5% different and some physical properties improved - were analyzed. Different pad thicknesses were used to perform the tests, aiming to understand the contribution of the compressibility on fluid displacement as a function of thicknesses. In order to isolate the system influence, stiff pads - made of steel - were also used, enabling the analyses of fluid displacement related only to the system strain. This study showed that friction material has a contribution of around 20% on fluid displacement, while other brake system components are responsible for the remaining displacement. It was also possible to identify that using higher brake application pressures the system contribution increases compared to the friction material influence.