The most common repair for drum brakes is to replace the brake shoes. Some drum brakes have a check hole on the back to see how much material is left on the brake shoes. When the friction material has worn to the point where the rivet is only 0.8 mm long, the brake shoes should be replaced. If the friction material is bonded to the rear bottom plate (not rivets), the brake shoes should be replaced when the remaining friction material is only 1.6 mm thick.

As is the case with disc brakes, deep scratches can sometimes appear in the brake drum. If the worn brake shoe is used for too long, rivets that hold the friction material in the rear will grind the drum out of the groove. A badly scratched drum can sometimes be repaired by regrinding. Disc brakes have a minimum allowable thickness, while drum brakes have a maximum allowable diameter. Because the contact surface is inside the drum, the diameter increases as you remove the material from the drum brake.

maintenance

As the lining wears away, more space is created between the brake shoe and the drum. When the car stops in reverse, it pushes on the brake shoe, making it close to the drum. When the gap becomes large enough, the lever shakes enough to move the regulator's gear forward one tooth. The regulator is threaded like a bolt so that it can be loosened a bit as it rotates and extended to fill the gap. Every time the brake shoes wear out a little, the regulator advances a little further, so it always keeps the brake shoes close to the drum. Some cars have regulators that start when emergency brakes are used. If the emergency brake is not in use for a long period of time, the regulator may not be able to adjust.

Therefore, if your car is equipped with such a regulator, use emergency brakes at least once a week.