In 2002 a mother and a child were injured and killed in an accident caused by a tire fallen out of the front left hub of a large tractor. Usually, in such an accident, engineering accident investigation is conducted thoroughly. However, it seems that this case of the engineering investigation by a specialist is insufficient since correspondence of a maker had too many problems. So, in this paper, I analyzed the accident carefully from a viewpoint of fracture mechanics. As a result, I got reasoning that the margin of safety ratio of the hub of accident vehicles was insufficient. A maker's engineers must also have had the same conclusion in the early stage. Why couldn't the maker recall these tractors independently?
