Abstract: A warning mechanism for detecting brake shoe wear is adapted to be fitted into a recess formed on the rear face of a brake shoe such that when the front face of the shoe, which undergoes frictional engagement during braking, is worn to a sufficient extent, a defaceable detection wire in the warning mechanism will be ruptured to provide an indication of depletion of the braking material of the shoe. The detector element is removably secured within the recess of the brake shoe and is located such that it will not be dislodged by a braking force applied to the brake shoe by a piston of the brake assembly but will, instead, be held in position thereby.