What happens to brake drums when they heat up?

When brake drums heat up, they expand away from the brake linings due to thermal expansion. When brakes are applied, friction generates heat, causing the temperature of the brake components, including the drums, to rise. As the temperature increases, the metal of the brake drums expands. This thermal expansion can lead to a larger gap between the brake drums and the brake linings. If the expansion is significant, it can result in reduced braking efficiency, as there is less contact area between the linings and the drums. This is an important aspect for drivers to understand, as overheating can also lead to brake fade, impacting vehicle performance and safety.