Budd–Michelin rubber-tired rail cars remained obscure in comparison with other competitors for the title, such as the "Pioneer Zephyr" and Union Pacific's M-10000. Rubber-tired rail cars achieved greater success in France, and similar rubber-tired subway cars have been adopted in Canada and Mexico as well as on numerous systems in Europe. During the 1920s, the American Budd Company, at the time a relatively obscure auto-frame supplier, developed an extensive working relationship with the French firm Michelin, which was best known for its tires. In 1929, Michelin built its first rail car, and by 1932 nine of its cars were in operating service, all of
United States Rubber Company brands. In 1940, U.S. Rubber purchased the remainder of the Gillette Safety Tire Company, and began to expand and modernize the Eau Claire factory, greatly increasing production. During World War II, U.S. Rubber factories were devoted to production of war goods, and produced military truck and airplane tires, as well as the canvas-top, rubber-soled Jungle boot for soldiers and marines serving in tropical and jungle environments. U.S. Rubber ranked 37th among United States corporations in the value of wartime production contracts. In 1942, the United States government restricted the sale of scarce rubber products for civilian use and production at