The complex of operational studies and theoretical research was performed on the occurrence of harmful wear that changes geometrical parameters of the useful contact area of the brake pads of freight cars at various established standard clearance between the pad and the wheel, which significantly impairs the braking efficiency of trains. The inspections of the mechanical part of the brakes attracted attention to the abnormal wear of the brake pads of the freight cars, which occurs because the common centre of gravity of the pad and the brake shoe, which are on the pendular suspension, do not coincide with the centre of the hole in the brake strut for any pad. The results of calculations using the coordinate method performed in the MathCAD software environment and the graphical one performed in AutoCAD to determine the geometrical parameters of the formation of the upper harmful wear of the pad depending on the standard clearance between the wheel and the brake pad were compared to proved theoretically that the error between them does not exceed 5-7%.