by Jody L. Campbell
As the brake shoes wear out from use, the water wheel cylinder has to push its pistons further outward so that the shoes come into contact with the inner diameter of the drum. When the brake shoe lining wears out, metal-to-metal contact will occur that can damage the brake drum. There are a couple of shoe styles, one riveted, the other glued, and they require slightly different ways of measuring. You can also measure the width of an installed shoe to compare to the inside diameter of the drum in the drum brake installation.