What is the most common failure for drum brakes?
The most common failure in drum brakes is worn or glazing brake shoes, which reduces friction and braking performance. Regular use wears the linings, and excessive heat can glaze the surface, diminishing bite and stopping power.
Understanding the failure in detail
Drum brakes rely on shoes pressing against a rotating drum to create friction. Over time, the friction material wears down, heat can alter its texture, and other components can degrade or fail. While wear is normal, several failure modes recur in service, often compounding braking problems.
In addition to normal wear, the following failure modes are frequently observed in drum brake systems.
- Contamination of the brake lining by oil, grease, or brake fluid, which can drastically reduce friction and lead to a soft or spongy pedal and poor braking performance.
- Improper adjustment or a malfunctioning self-adjuster, causing the shoes to not contact the drum evenly or to drag, which reduces bite and can overheat the components.
- Hydraulic leaks in the wheel cylinder, leading to a loss of hydraulic pressure and reduced braking force at the affected wheel.
- Overheating that can glaze the shoe lining or drum surface, making the material harder and less effective at creating friction.
- Rust, corrosion, or scoring of the drum or backing plate that causes the shoes to stick, seize, or not release properly, resulting in dragging or uneven braking.
In short, while wear is expected, the most significant and common failures are those that diminish friction or prevent full engagement between the shoes and the drum, including contamination, improper adjustment, hydraulic issues, glazing, and corrosion.
Preventive steps and maintenance
Proactive maintenance helps reduce the risk of these failures and keeps drum brakes functioning reliably. The following steps are commonly recommended by technicians.
- Schedule regular inspection of the brake shoes, drums, and wheel cylinders for wear, leaks, and scoring.
- Check for oil or grease contamination on the shoes and replace contaminated linings and seals as needed.
- Test and correct brake adjustment, and service the self-adjuster to ensure even contact with the drum.
- Inspect drums for scoring, out-of-round conditions, and replace them if necessary.
- Bleed and replace brake fluid as required to maintain proper hydraulic performance.
Proper maintenance — including timely shoe and drum replacement, cleaning, and attention to hydraulic integrity — is essential to prevent the most common drum-brake failures and sustain effective braking performance.
Summary
Drum brakes most commonly fail due to worn or glazed brake shoes, which reduce friction and stopping power. Other frequent issues include contamination by oil or brake fluid, improper adjustment, hydraulic leaks, overheating leading to glazing, and corrosion that causes sticking. Regular inspection and timely replacement of worn components are key to maintaining reliable drum-brake performance.
What is the life expectancy of drum brakes?
around 150,000 to 200,000 miles
Drum brakes are designed to be operable for around 150,000 to 200,000 miles, while the shoes are meant to last for 30,000 to 40,000 miles. These values, however, are rated for regular driving conditions, and various factors could affect the longevity of the brake drums.
What is the biggest problem with drum brakes?
Cons. Overheating – One of the biggest downsides to drum brakes is their tendency to overheat quickly in conditions where a driver has to brake frequently.
How do drum brakes fail?
Springs can break from fatigue if not replaced along with worn brake shoes. And the drum and shoes can become damaged from scoring if various components (such as broken springs or self-adjusters) break and become loose inside the drum.
What is the 30/30/30 rule for brakes?
Techs can help to prevent brake fade through these actions: After brake pad installation, you can bed-in your customer's new hardware by following the 30-30-30 rule, which means 30 stops from 30 miles per hour and 30 seconds of cool down time in between each stop.
