Vehicle brake friction output is influenced by the performance of many brake corner system components. For the highest and most table friction output, each component needs to work properly. For each component of the brake corner system, there are many factors related to the final corner friction value. This paper focuses on the relationship between the chemical composition of a cast iron brake rotor chemical contents and the friction output value. Alloying elements have complex interaction effects. In this paper, a numerical analysis tool is applied to dyno bench test results to forecast braking friction values for specific cast rotor chemical compositions. To see why some rotors can achieve high friction values, the rotor microstructure is analyzed. An optimal rotor casting chemical composition recipe, based on set formula and DFSS method, is recommended.