A medium sized duty truck was turning into a construction zone along a curve from one highway to another. Suddenly, the left front brake locked causing a sharp left turn. The truck impacted a concrete construction barriers. Six weeks prior, the truck had a complete brake overhaul. Visual and microscopic examination of the left front brake shoes and other debris contained within the truck wheel and brake drum revealed a loose and highly deformed castellated nut and washer. The brake shoes were visibly damaged and the castellated nut exhibited imbedded brake lining material. Photograph A shows an overall view of the subject brake lining.
Photograph A Brake shoe from subject truck.
This failure and accident occurred as a result of improper installation of the castellated nut during brake shoe replacement and brake overhaul. The brake lining imbedded castellated nut is shown in Photograph B.
Photograph B Deformed castellated nut and embedded brake shoe material from brake shoe assembly.