Comparing Brake Options: Disc vs. Drum
Brakes are at the forefront of safety considerations in the transportation industry. With brake violations making up almost half of out-of-service roadside inspection violations on commercial vehicles, hauling companies are eager to make wise investments in brakes.
For decades, shoe-and-drum brakes have been the mechanism of choice for the vast majority of truck buyers and fleet owners. While that remains the case, disc brakes recently made their way onto the trucking scene, and seem to be gaining popularity among drivers and operators. Newest isn’t always best, however. Sometimes a longer track record is more insightful and advantageous when making a long-term investment. Here are some things to consider when evaluating the difference between discs and drums.
How They Work: Disc Brakes
In vehicles with disc brakes, calipers hold brake pads that clamp down around a rotor, mounted to the hub of the wheel, when the brakes are applied. They work similarly to bicycle brakes, but on a larger scale—by gripping and slowing the spinning of wheels through the friction of the pads on the rotors. Unlike car brakes that operate hydraulically, truck brakes rely on compressed air as a power assist, since it’s more reliable and powerful for larger, heavier vehicles.
Pros and Cons
In the trucking industry, the use of disc brakes is still relatively new. Among their benefits, sources say that they can reduce stopping distance and quicken the pace at which a vehicle comes to a complete stop. That being said, the margin of difference over newer drums may be negligible.
Disc brakes are also self-adjusting, and are easier and quicker to change than drums. The downside is that disc brakes don’t last as long as drum brakes, and thus need to be replaced more often. They’re also more expensive than drum brakes. That may be why they’re used by only about 10 percent of heavy truck buyers surveyed by TruckingInfo.com. Analysts predict that it will be 10-15 years before they’re more readily embraced by the industry.
How They Work: Shoe and Drum Brakes
Still the brake of choice for about 95 percent of the U.S. heavy-duty truck market, shoe and drum brakes work similarly to disc brakes, by applying pressure to a spinning surface (in this case, a drum). When the brake pedal is engaged, the piston presses the brake shoes against the drum to slow movement.
Pros and Cons
Drum brakes have many advantages: they are less expensive to manufacture and last longer than disc brakes. Maintenance teams appreciate their long life because the weight of drum brakes makes them more difficult to replace. Drum brakes can also easily incorporate an emergency brake mechanism, making them a strong choice for safety.
Considering recent innovations and improvements to both disc and drum brakes, the decision between the two brake types really comes down to preference. Some companies have embraced the switch to disc brakes, while the majority have stayed with tried-and-true shoe-and-drum brakes for their reliability, low cost and less-frequent need of service. At the end of the day, companies base the decision on expert insight and research by their technicians and maintenance staff, along with their consideration of their fleet and their needs.