Your car’s safety really depends on its brakes. If your car has brake drums (usually found on the rear wheels of older cars, though some newer ones use them for the parking brake), it’s crucial to address any wear or damage right away. If your car is having trouble braking, stop driving it immediately and have it towed to a repair shop.

Here are some signs that your brake drums might be going bad:

Simple Signs of a Bad Brake Drum

Noise: When the brake pads (called “brake shoes” in drum brakes) wear down, their metal backing plate starts to rub directly against the metal of the brake drum. This will cause a loud, unpleasant metallic scraping or grinding noise every time you brake.
Low Brake Pedal: If your brake pedal feels like it goes too far down before the brakes engage, it could be due to too much space between the brake shoe and the drum. Often, cleaning and adjusting the brakes can fix this. However, it could also point to a more serious problem like a brake fluid leak or a bad master cylinder.
Spongy Brake Pedal: If the brake drums are cracked or worn very thin, they can cause the brake pedal to feel “spongy” or soft when you press it. (Keep in mind, a spongy pedal is most often caused by air in the brake lines, but a bad drum is another possibility.)
Brake Pedal Pulsation: If your brake drums are “out of round” (meaning they’re no longer perfectly circular), the brake shoes won’t make even contact with them. This causes the shoes to bounce slightly, and you’ll feel a pulsing or vibrating sensation in the brake pedal when you brake.
Parking Brake Doesn’t Hold: In extreme cases, if the brake drums are worn too thin, the brake shoes might not be able to make enough contact to hold the car. You might notice a loud “pop” when you put an automatic car in gear after parking on a slope, or your parking brake lever/pedal might be too easy to engage or won’t stay put once released.

How to Fix the Problem

Before spending money on new brake drums, a thorough inspection is a must. Drums that are too thin can crack and break when they get hot, or their surface can become “glazed” (shiny and slick), which reduces braking power.

In some cases, a mechanic might be able to resurface (grind down to a smooth, even surface) a problematic drum. Sometimes, just cleaning and adjusting the brakes can help.
A mechanic will measure the inner diameter of the drum and compare it to what the manufacturer recommends. If it’s too worn, it will definitely need to be replaced.
Brake shoes should always be replaced whenever the drums are swapped out or resurfaced. This ensures that the new shoes wear evenly with the drum. Because drum brake shoe replacement involves many small springs and can be tricky, it’s generally best left to a professional mechanic.

How Brake Drums Work

Brake drums and shoes used to be on almost every car, but these days, they’re typically only found on the rear wheels, and even that’s becoming less common as most new cars use disc brakes on all four wheels. However, many existing vehicles still have them, and even cars with disc brakes often use a smaller drum-and-shoe setup for the emergency brake.

Brake drums are circular metal cups that enclose the brake shoes. When you press the brake pedal, the brake shoes push outwards against the inside of the drum, creating friction that slows the wheel down.

Here’s a quick overview of how the drum brake system works:

The master cylinder takes the force from your foot on the brake pedal and turns it into hydraulic pressure using brake fluid.
This pressurized fluid travels through brake lines to the wheel cylinders, which are small parts located inside the drum, between the brake shoes.
The fluid pressure makes the wheel cylinders push the brake shoes outwards, pressing them firmly against the inner surface of the brake drum.
This contact creates the friction needed to bring your vehicle to a halt.