The Ins and Outs of Brake Drums

How Brake Drums Help Stop Your Semi-Truck

Chances are, if you drive a semi-truck, your air brake system has brake drums included as one of its main components. But anyone who's been driving truck for any amount of time already knows that. However, if you've ever had any questions about your brake drums, how they work, when they need to be checked, or what the difference between disc and drum brakes are, then you've come to the right place. Our team of trucking experts has put together the following guide to help you learn more about one of your brake system's most important features.

What Are Brake Drums?

First of all, you may be wondering precisely what the definition of a brake drum is. A brake drum is a cylinder that is attached to the top of the vehicle's wheel hub. Brake drums are typically affixed to a rotating shaft or wheel against which brake shoes or bands act.

It is the responsibility of the brake drum to accept, store, and dissipate heat when braking – that way they can work at effectively stopping your vehicle. There are three factors that can increase the heat in the brake drums – velocity, weight, and deceleration. The amount of heat a brake drum can dissipate is directly dependent on design. A better design means more heat is dissipated and braking is more efficient.

How Do Brake Drums Work?

So, how do brake drums work? The answer is simpler than you might think. The brake drum surrounds a set of brake shoes that are coated in materials that generate friction. When the brake pedal is pressed, these shoes are pushed outwards against the inner surface of the brake drum, generating the sought-after friction, thus slowing the vehicle down.

What Is The Difference Between Brake Drums and Rotors?

Available today, there are two kinds of brakes – disc and drum brakes. Disc brakes are made with a rotor that spins along with your wheels. To stop your wheels, brake pads located inside the caliper, press against the rotor to stop it from rotating. When you choose drum brakes, the drum spins along with the wheel instead of the rotors.

What Are The Advantages of Drum Brakes?

With drum brakes, there is more braking force than is available in equal diameter disc brakes. Drum brakes are longer lasting because they have more of an increased friction contact area than disc brakes typically do. Another advantage to drums brakes is that they are also cheaper to manufacture and maintain than disc brakes.

How Many Brake Drums Does a Semi-Truck Have?

There are a number of brake drums in your semi-truck's air brake system. But how many should you look for? Typically, a semi-truck with five axles and 18 wheels has 10 brake assemblies, and therefore has 10 brake drums. It's important to look over each one when you are checking the components in your air brake system.

When Should Brake Drums Be Replaced?

On average, semi-truck brake drums should be replaced every 100,000 miles. However, it often depends on how they are used. With certain applications, your brake drums can last longer than with others. Your best bet is to replace the brake drums in your air brake system whenever you feel the brake pedal going soft.

Selecting the Right Brake Drum

Brake drums are not all alike, so it's important to be mindful when choosing which ones are right for your semi-truck. You'll want to choose your brake drum based on your specific application. For instance, chamber size, length of slack adjuster, type of friction material, tire size, frequency of stops, time interval in between stops, and the aerodynamics of the vehicle are all factors you'll want to consider when choosing new brake drums.

As an example, applications with a 23,000 GAWR with a high frequency of stops creates heat that a standard brake drum can't handle. In this case, you'll need a heavier drum. Each brake drum has different sized holes designed to dissipate heat.

Shop Brake Drums Now!

Now that you know more about the brake drums in your air brake system, the next step is to find which one is right for you in our online store.

Have you been on the lookout for an aftermarket brake drum for your semi-truck's air brake system? If so, then you've come to the perfect place! We have a full assortment of brake drums and air brake parts for you to choose from.

Want to know more about your air brake system? If so, take a look at our posts on air brakes, slack adjusters and brake chambers.