Brake pads lining and brake linings are friction materials that help convert a commercial vehicle’s movement into heat so the vehicle can slow or stop. Brake pads are normally used with disc brakes, while brake linings are fitted to brake shoes used inside drum brakes.
Although the terms are sometimes used interchangeably, they describe different components.
For fleet operators, mechanics and commercial vehicle owners, understanding this distinction is important when inspecting brake wear or ordering replacement parts. A truck may use drum brakes, disc brakes or different configurations across its axles, so the correct friction component depends on the actual braking system installed.
For a broader explanation of these configurations, see our guide to the types of truck brakes.
What Is the Difference Between Brake Pads Lining and Brake Linings?
The main difference is the type of wheel-end brake in which the friction material operates.
Brake pads are used in disc brakes. They contain friction material attached to a backing plate. When the brakes are applied, the brake caliper presses the pads against both sides of the rotating brake disc or rotor.
Brake linings are commonly used in drum brakes. The friction material is attached to a curved brake shoe. During braking, the shoes move outward so the linings contact the inner surface of the brake drum.
How Do Brake Pads and Linings Stop a Heavy Vehicle?
A moving commercial vehicle contains kinetic energy. When the driver applies the brakes, the braking system creates force at the wheel ends.
The pads or linings press against a rotating disc or drum. Friction then converts part of the vehicle’s kinetic energy into heat.
Heavy trucks can generate considerable heat during braking because of their vehicle weight, payload and operating conditions. Friction materials must therefore provide predictable braking performance while tolerating repeated heating and cooling cycles.
In vehicles equipped with air brakes, compressed air ultimately provides the force required to operate the foundation brakes. Our guide to the truck air brake system explains how compressors, reservoirs, valves and brake chambers work together before braking force reaches the wheel end.
What Are Commercial Vehicle Brake Pads Made Of?
A brake pad generally consists of a metal backing plate with a specially engineered friction compound attached to it.
Friction compounds can contain combinations of fibres, fillers, binders, lubricants, abrasives and metallic or mineral materials. Exact formulations vary according to manufacturer and application.
Friction materials are sometimes described using broad categories such as:
- Organic or non-asbestos organic formulations
- Low-metallic formulations
- Semi-metallic formulations
- Ceramic-containing formulations
However, choosing a commercial vehicle brake pad should not be based on the material category alone.
A suitable pad must match the braking system, vehicle application, axle, operating temperatures and manufacturer’s requirements. Two pads with similar external dimensions may not necessarily have the same friction characteristics or be interchangeable.
What Causes Brake Pads and Linings to Wear Out?
Brake friction materials are designed to wear gradually during use. The rate of wear, however, can vary significantly between vehicles.
Factors affecting brake-pad and lining life include:
- Vehicle weight and payload
- Number of braking events
- Urban versus highway operation
- Hilly or mountainous routes
- Driving technique
- Brake adjustment
- Brake drag
- Disc or drum condition
- Friction-material specification
- Operating temperature
- Contamination
- Condition of related brake components
For example, a city delivery truck making hundreds of stops can experience a very different wear pattern from a long-haul truck spending most of its journey at steady highway speeds.
For this reason, there is no single replacement mileage suitable for every commercial vehicle brake pad or lining.
What Does Uneven Brake Pad or Lining Wear Mean?
Uneven wear can indicate that another part of the braking system requires attention.
Possible causes include:
- Brake drag
- Sticking caliper components
- Incorrect brake adjustment
- Damaged brake drums or discs
- Actuator or brake chamber problems
- Unequal braking force
- Incorrectly fitted components
If one wheel end wears significantly faster than another, simply installing new friction material may not solve the problem.
The underlying cause should first be identified. Our guide to common semi-truck brake problems explains brake drag, overheating, uneven braking and other symptoms in greater detail.
What Is Brake Glazing?
Brake glazing occurs when the friction surface becomes unusually smooth or hardened, often after excessive heat or inappropriate operating conditions.
A glazed friction surface may not generate the expected braking characteristics and can sometimes be associated with noise or changes in braking response.
The friction material should not automatically be blamed, however. Excessive temperatures may result from brake drag, incorrect adjustment or other mechanical problems.
When glazing or abnormal heat damage is found, technicians should inspect the surrounding brake system to determine why it occurred.
Can Oil or Grease Damage Brake Friction Material?
Yes. Brake pads and linings rely on controlled friction, so contamination can seriously affect their performance.
Possible contaminants include:
- Oil
- Grease
- Brake fluid
- Hub or axle lubricant
- Other foreign material
Contaminated friction material should be assessed according to the brake and vehicle manufacturer’s procedures. The source of the contamination must also be repaired; otherwise replacement friction material may quickly become contaminated again.
Leaks near the hub, wheel end or hydraulic components should therefore never be treated as only a cleaning issue.
How Do You Know When Brake Pads or Linings Need Replacement?
Commercial vehicle brake friction components should be inspected according to the vehicle manufacturer’s maintenance requirements and applicable wear limits.
During an inspection, technicians may check:
- Remaining friction-material thickness
- Uneven wear
- Cracking or physical damage
- Glazing
- Contamination
- Condition of the backing plate or brake shoe
- Disc or drum condition
- Wear indicators or sensors
- Signs of excessive heat
Some braking systems incorporate mechanical or electronic wear indicators. These can help identify wear, but they should not replace scheduled physical inspection.
Friction material that has reached its specified wear limit should be replaced before continued use damages associated components.
Should Brake Pads Be Replaced Together With Brake Discs?
Not necessarily, but the brake disc must be inspected when pads are replaced.
The disc should be assessed for condition, wear, scoring, cracking and its applicable thickness specification. A new set of brake pads cannot correct a disc that has already become unsuitable for service.
Similarly, when replacing drum-brake linings, the brake drum and related components should be inspected.
The purpose is to treat the brake as a system rather than replacing one wear component in isolation.
If you are budgeting for replacement, see our guide to commercial vehicle brake pad replacement cost.
Choosing the Correct Commercial Vehicle Brake Pads and Linings
Correct fitment is particularly important for braking components.
Before ordering replacement pads or linings, identify information such as:
- Vehicle manufacturer
- Truck or bus model
- Production year
- Axle position
- Brake manufacturer
- Brake model or size
- Original equipment or cross-reference part number
- Pad or lining dimensions
Do not assume that a visually similar brake pad is compatible. Commercial vehicles can use different brake systems even within the same vehicle model range.
Using the vehicle details together with the part number is usually a more reliable way to narrow down the correct replacement.
If you need assistance identifying the correct brake pads, brake shoes, brake linings or other braking components, contact our sales representative with your vehicle details, dimensions or OE part number.