Whenever the brake drums are removed, they should be checked for wear and damage. Light scoring of the friction surface is normal, but if it is excessive or if the internal diameter exceeds the specified wear limit, the drum and hub assembly should be renewed. After high mileage, the friction surface may become oval. In such cases, it may be possible to have the surface ground true by a qualified engineering works; however, it is preferable to renew the drum and hub assembly.