Surface Finish

Normal light scoring of the drum surfaces not exceeding 0.51 mm (0.020 inch) in depth will not affect brake operation. Slight scoring can be cleaned up with fine emery cloth. Heavy or extensive scoring causes excessive shoe wear. The drum braking surface will need machining to remove these scores. If the drum is grooved and the brake shoes are slightly worn, the drum should not be machined. Instead, polish the drum braking surface with fine emery cloth. Eliminating all of the drum grooves and ridges on the shoes would require removing to much metal and pad material.