Buzz
In many cases, it’s more convenient to take your vehicle to a professional mechanic instead of attempting to replace brake components yourself.
©iStockphoto/Alina Solovyova-VincentAmong the most frequent maintenance tasks for any car is brake replacement. When the brakes feel soft or produce squeaking noises, it’s time for action. You might choose to replace brake shoes on your own, or you could opt for professional assistance. But what keeps all these brake components in place? In drum brake systems, the crucial yet often overlooked components are the brake backing plates.
As defined by AutoZone.com’s automotive glossary, brake plates are "stamped steel plates that support the wheel cylinder and secure the brake shoes; these metal plates act as the base for brake shoes and other drum brake components" [source: AutoZone].
Without backing plates, the brakes would lack a stable foundation. For friction to effectively halt the vehicle, the brake shoes need to be securely anchored — a role fulfilled by this essential brake component.
The term "backing plate" can sometimes cause confusion, as it is also used to describe a component in disc brake systems. In such systems, the brake shoes feature a backing plate where the friction material is attached, either by glue or rivets. These plates are comma-shaped, unlike the shallow, dish-like backing plates in drum brakes, which include holes for fasteners.
Now that we’ve identified the location and appearance of the backing plate, let’s delve deeper into its role and functionality.
Function of Backing Plates
When you press the brake pedal, your braking system — supported by backing plates — springs into action.
Ryan McVay/Photodisc/Getty ImagesBacking plates play a crucial role in maintaining the integrity of the braking system, ensuring it functions correctly. In drum brake setups, each wheel features two curved brake shoes attached to a stationary backing plate. These shoes, shaped like the letter C and coated with friction material on their outer curve, are fixed to both sides of the brake plate. This entire assembly is housed within a cast-iron drum that rotates with the wheel. Springs keep the brake shoes in position, preventing contact with the drum when the brakes are not engaged.
Pressing the brake pedal increases pressure on the hydraulic fluid in the brake lines. At the top of the backing plate, a wheel cylinder contains two pistons, one at each end. The pressurized brake fluid enters the cylinder, forcing the pistons to move outward. This action pushes the brake shoes against the inner surface of the brake drum.
The friction material on the brake shoes interacts with the drum’s inner surface, creating the force needed to stop the car. However, without the backing plates providing stability and securing all brake components, the system would fail to function effectively.
For additional insights into backing plates and the mechanisms that bring your vehicle to a stop, continue reading on the next page.
