On many vehicles, drum brakes are an integral part of the braking system. When so equipped, they’re typically found on the rear wheels of a vehicle. They not only slow and stop your vehicle, but also may function as the parking or emergency brake. Drum brakes work on the same principle as disc brakes. When the brakes are applied, hydraulic pressure forces the brake shoes OUT, against the inside of the brake drum. This creates the friction required to slow and stop the vehicle. When the pressure is released, return springs pull the shoes back to their original position, allowing the wheel to turn freely. Springs lose their resiliency, and brake shoes and drums wear out over time. We recommend inspecting both front and rear brakes regularly. Brake shoes should be replaced when the remaining friction material is measured at 2 mm or less, brake drums when they exceed their maximum diameter, and brake hardware as required. Ask your service advisor to measure the thickness of the drums every time your brakes are serviced, as worn-out drums might not have enough metal left for safe braking. Over time, brake drums may wear unevenly, causing vibration and/or noise. A worn-out brake drum may contribute to premature brake shoe wear, leading to more frequent shoe replacement and higher repair costs. From a safety standpoint, worn brake drums may dramatically increase the distance required to stop, cause the vehicle to pull to one side, or result in loss of control, all of which could cause injury to you and others. Neglecting brake drum maintenance has no environmental impact.