Brake shoes are crescent-shaped metal components with a friction lining. When you pull the brake lever, a cam rotates and pushes the shoes outward against the inside of a rotating drum, creating the friction needed to stop.
Squealing or Grinding: A high-pitched noise usually means the friction material is thin.
Spongy Lever: If you have to pull the lever all the way to the grip before the bike slows down.
Vibrations: "Juddering" during braking can indicate uneven wear or a warped drum.
Wear Indicator: Most modern bikes have a small arrow on the brake arm. If it points to the "wear limit" mark when the brake is applied, it’s time to replace them.