Disc Brakes vs. Drum Brakes For Semi-Trailers

As a professional truck driver, you know the road can throw unexpected challenges your way. Navigating treacherous weather, heavy traffic, and varying road conditions requires skill, experience, and the right equipment, including reliable brakes.

Semi-trucks rely on brake performance to stop in a controlled manner, especially in emergencies. Inclement weather aside, a fully loaded semi-trailer requires approximately 250 feet — almost the entire length of a football field — to come to a complete stop when traveling at 60 miles per hour.

With this in mind, the braking system should be a high priority when shopping for a new or used commercial semi-trailer.

Choosing the right brake system for your semi-trailer

Commercial trucks commonly use two types of trailer brakes — disc brakes and drum brakes. Although both operate on an air brake system, they perform quite differently. 

What are disc brakes?

Disc brakes use a flat disc (rotor) squeezed between brake pads to generate friction and bring your semi-truck to a stop. 

Air pressure is applied to the calipers when you press the brake pedal. The air pressure forces the pistons inside the caliper to move. As the pistons move, they exert force on the brake pads. The brake pads are pressed against both sides of the rotor, creating friction. The friction generated by the brake pads and rotor slows down the wheel's rotation and stops your truck. 

Because of their efficient design and fast response times, disc brakes have gained popularity in recent years.

What are drum brakes?

Drum brakes also work as a result of air pressure. But in this system, brake shoes press against the interior of a drum to create the necessary friction for braking. 

Instead of squeezing a rotor, air pressure moves the slack adjuster which in turn rotates a cam which applies the brake shoes against the inner surface of the brake drum. This expansion creates friction and slows down wheel rotation on your semi-trailer until it comes to a complete stop.

Which braking system has the best stopping power?

Stopping power refers to a brake system's ability to effectively slow down or stop a vehicle, even under demanding conditions. While you'll never have the option to 'stop on a dime,' your stopping power is impacted by the braking system you choose for your semi-trailer.

Disc brakes react swiftly compared to drum brakes — a quick response can be the difference between a safe, controlled stop and a potential collision.

Which trailer braking system is more resistant to brake fade?

As a professional trucker, you're familiar with the heat generated during prolonged braking, particularly on downhill descents. Heat buildup can lead to a phenomenon known as "brake fade," where the braking performance gradually deteriorates due to excessive heat. 

Brake fade is a potential safety hazard, especially when hauling substantial loads through hilly terrain and driving on busy highways.

Because of their enclosed design and surface area, heat can get trapped in drum brakes, subjecting them more to brake fade. 

On the other hand, the open design of disc brakes allows heat to disperse more rapidly, preventing brake fade and maintaining consistent performance. This is particularly critical when driving in dangerous conditions.

The most popular semi-trailer braking system

Although drum brakes have dominated the trucking industry for years, disc brakes are growing in popularity. 

For many years, drum brakes have been the norm for America’s trucking industry. However, with recent advancements in technologies and better materials, disc brakes are becoming more widely used in the industry. New technology and a lower cost of maintenance are generating new disc brake users every day.

Lifespan and cost of drum brakes vs. disc brakes

When choosing between disc brakes and drum brakes for your semi-trailer, considering the lifespan and cost is essential. These factors impact your budget and how frequently your semi-trailer is off the road for repairs, costing you time and money in maintenance and lost wages.

Advancements in brake technology, such as better friction materials and improved heat dissipation mechanisms, extend the lifespan of both disc brakes and drum brakes. However, these benefits are generally more noticeable with disc brakes due to their superior heat dissipation capabilities.

Drum brakes, while durable, tend to exhibit uneven wear patterns. The brake shoes are susceptible to uneven wear from consistently hauling heavier loads, driving in hilly or mountainous terrains, or driving on congested highways with regular abrupt stops. 

While similar driving and road conditions can also impact the lifespan of both disc and drum brakes, you can do some things to prolong the life of your trailer brakes. 

Prolonging the lifespan of both trailer brake systems involves regularly checking your equipment and mindful driving practices. Avoiding panic braking — sudden and aggressive braking — can prevent unnecessary wear. Instead, use steady, even pressure to stop your semi-trailer and reduce stress on the brake components.

Drum brakes might have a lower initial cost, but disc brakes often prove more cost-effective in the long run. Their extended lifespan and reduced maintenance needs can offset the higher upfront investment.

Regulations and safety standards

As with any aspect of trucking, regulations play a pivotal role. Depending on your jurisdiction, specific requirements regarding the type of brakes allowed on semi-trailers might exist. It's essential to stay informed and ensure your truck complies with the relevant regulations.

Maintenance and repair of your braking system

Keeping your commercial truck in optimal working order is priority number one. Whether you have disc brakes or drum brakes, maintaining your braking system is one of the many important semi-trailer parts to keep an eye on. 

However, if it's the ease of maintenance and repair that you're after, disc brakes win hands down. Their straightforward design and accessibility make inspections and replacements easy.

Learn more about your braking system

Still have questions about which braking system is best for your new or used semi-trailer? 

Stop by a CRTS semi-trailer sales location and chat with a professional. 

With five centrally located sales centers in the South Atlantic and more than 50 years of experience, you'll quickly learn everything you need to know about disc brakes and drum brakes for a safe experience on the road.