In 1992 the National Transportation Safety Board (NTSB) commissioned a report to study the causes of wheel separations from medium and heavy duty trucks. The report showed that on average between 750 and 1050 wheel separations were reported in the United States each year. Remarkably the report went on to conclude that “… the leading causes of wheel separations from medium and heavy duty trucks are improper tightening of wheel fasteners…” This is merely one, poignant example of many, illustrating the importance of getting the fastener tightened properly. In fact, one can make the claim that “properly tightened joints seldom come loose”.(…)
via Demystifying Bolt Preload | Fasteners content from Machine Design.