Wheel Separation from Ford Vehicles

Recently, Ford announced a new recall for its 2010-2011  Fusion and Mercury Milan vehicles.  It seems that the lug studs can break and cause a wheel to separate from the vehicle.  Needless to say, wheels are not supposed to separate from the vehicle while the vehicle is in motion.  However, in over 20 years of engineering investigations, I have only seen two instances where I felt that wheel separation in a crash senario was the fault of the manufacturer.  Both cases involved 90s model Ford trucks; an F150 and a Ford Ranger.  Both cases also involved impact with another object, the F150 with another vehicle and the Ranger with a wire fense and post.  During the course of each investigation, each wheel was found intact but away from the area of final rest of the trucks.  The brake calipers were also found attached to each wheel rim.  However, the cotter pin that prevents the spindle nut from turning was missing in both cases.  But, more to the point, the threads on the spindle shaft were undamaged in both cases suggesting that the nut had unwound allowing the wheels to separate before the impacts occurred. Incidentally, the findings appeared to corroborate the stories of each driver.

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