Major auto racing events are usually named `` Grands Prix '' ( plural form of `` Grand Prix '' ) , a tradition dating back to the first decade of the 20th Century and the Grand Prix motor racing of the 1920s and 1930s .
Major auto racing events are usually named `` Grands Prix '' , a tradition dating back to the first decade of the 20th Century and the Grand Prix motor racing of the 1920s and 1930s .