What’s the biggest problem with drum brakes?

The biggest problem with drum brakes is heat management: they trap heat and are more prone to brake fade during repeated or sustained braking, which reduces stopping power and demands more pedal effort. This vulnerability, rooted in their enclosed design, becomes apparent on long descents, in stop‑and‑go driving with heavy loads, or after aggressive braking, and explains why disc brakes dominate in performance-critical applications.

Why heat is a drum brake’s Achilles’ heel

Drum brakes operate with brake shoes pressing outward against the inside of a rotating drum. Because the drum is an enclosed, relatively heavy shell, it sheds heat more slowly than a ventilated disc. As temperature climbs, several things happen at once: the friction material’s coefficient drops (pad “fade”), the drum expands away from the shoes (reducing contact pressure), and, in extreme cases, the hydraulic fluid in the wheel cylinder can boil (causing long or spongy pedal). Together, these effects reduce braking torque and driver confidence precisely when strong braking is needed.

Disc brakes, by contrast, are exposed to airflow and typically ventilated, so they cool faster and resist fade better. That’s why front brakes—responsible for most stopping work—are almost universally discs in modern cars, and discs are preferred for high-performance or heavy-duty use.

How it shows up on the road

Brake fade in drums tends to appear under sustained or repeated braking: descending a mountain pass, towing, hauling passengers or cargo in hot weather, or navigating frequent stoplights. In wet conditions, drums can also be slower to clear water than discs, dulling initial bite. Drivers might notice the vehicle needs more distance to stop, emits a hot-brake smell, or pulls to one side if one drum heats more than the other.

Common symptoms drivers notice

The following points outline how heat-related fade and associated issues typically feel from behind the wheel.

• Longer stopping distances after repeated or prolonged braking.
• Increased pedal effort with diminished response, or a pedal that travels farther if fluid overheats.
• Acrid brake smell or visible wisps of smoke after heavy use.
• Pulling to one side as one drum fades faster than the other.
• Parking brake grip that seems weaker immediately after hard stops.

When these symptoms appear, allowing the brakes to cool, reducing load, and planning for extra stopping distance are prudent; a post-trip inspection can catch glazing, fluid degradation, or adjustment issues.

Design traits that exacerbate fade

Several inherent features make drums more susceptible to fade than discs. The enclosed drum traps heat, slowing convection. Thermal expansion increases the drum’s diameter, backing it away from the shoes and reducing contact pressure. Many drum designs are “self-energizing” (servo action), which lowers required pedal effort at normal temperatures but becomes much less effective once the friction coefficient drops with heat—so effort spikes just as stopping power falls. Dust and moisture can linger inside the drum, and automatic adjusters can stick, compounding performance losses until serviced.

Why many cars still use them in back

Despite their limitations, drums remain common on rear axles of budget cars and even some modern EVs (for example, certain European-market models) because the rear brakes handle a smaller share of braking heat, drums integrate the parking brake inexpensively, and the sealed design can resist corrosion in low-use scenarios. In EVs with strong regenerative braking, rear friction brakes see less duty, further lowering the risk of fade in everyday driving.

What you can do to mitigate the weakness

Drivers and fleets can reduce the risk and severity of drum brake fade with good technique, maintenance, and equipment choices.

1. Use engine braking on descents: downshift or select lower gears to offload the friction brakes.
2. Brake in intervals on long grades to let drums cool between applications.
3. Keep shoes properly adjusted and the hardware clean; ensure automatic adjusters operate freely.
4. Install quality friction linings and replace old brake fluid on schedule to raise fade resistance and boiling margins.
5. Consider rear disc conversions or front brake upgrades if towing, hauling, or driving in mountains frequently.
6. For heavy vehicles, use retarders or engine brakes (e.g., Jake brakes) to preserve drum capacity.

These practices maintain stopping performance under stress and extend component life, especially in heat-intensive conditions.

Heavy vehicles and fleets

Many medium- and heavy-duty trucks still use air-actuated drum brakes thanks to durability, cost, and integration with parking systems. Modern materials, finned drums, and better cooling have improved fade resistance, but long downhill grades can still overheat them. Fleet protocols—pre-trip inspections, correct brake balance, proper slack-adjuster function, and mandated use of engine retarders on descents—remain essential to avoid fade-related incidents.

Bottom line

Drum brakes’ primary liability is thermal: they dissipate heat poorly, making them prone to fade under repeated or sustained braking. For daily commuter use—especially on the rear axle—they’re adequate and cost-effective. But for heavy loads, mountain driving, or performance demands, disc brakes’ superior cooling and consistency are the safer, more reliable choice.

Summary

The biggest problem with drum brakes is heat-induced fade caused by their enclosed design and self-energizing mechanics, which together reduce stopping power during sustained or repeated braking. While drums remain practical on rear axles and in some EV applications, proper technique, maintenance, and, where appropriate, upgrades are key to keeping braking performance consistent when temperatures climb.

Why don’t they use drum brakes anymore?

Drum brakes are archaic – the concept has been around since Roman times. They have their advantages in some applications – slow heavy vehicles, chariot races – but disc brakes are hands down better for most automotive applications. Lower unsprung weight, better stopping power, and less heat fade.

What is the main problem with drum brakes?

Worn brake shoes are one of the most common problems with drum brakes. Symptoms of wear include: Reduced braking efficiency. Longer stopping distances.

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.

Are drum brakes reliable?

Even though disc brakes have become more common, drum brakes are still effective when properly maintained. They help your car stop safely and support your emergency brake system.