History of Brake Pads in Car
Brake pads are a critical component of a vehicle’s braking system. They are responsible for providing the friction required to slow and stop a vehicle’s wheels. Brake pads consist of a metal backing plate with friction material bonded to it. This friction material presses against a vehicle’s brake rotor or drum when the brakes are applied, creating friction that converts the kinetic energy of the moving wheels into heat energy. This heat is dissipated by the rotors and drums to slow the vehicle down.
Brake pads are designed to withstand high temperatures and pressures generated during braking. They are engineered with optimal friction coefficients and heat dissipation capabilities based on the type of vehicle they are used for. As brake pads wear down from use, they need to be periodically inspected and replaced to maintain proper braking performance. Keeping brake pads in good condition is crucial for safe operation of any vehicle relying on a friction braking system.
Early Braking Systems
Before the invention of modern brake pads, early automobiles used very rudimentary braking systems. The first braking mechanism was invented in 1803 by Richard Trevithick, who used wooden blocks that pressed against iron wheels to slow down locomotives. Wooden blocks continued to be used in horse-drawn carriages and early automobiles in the late 1800s. However, these wooden blocks wore down quickly and provided inconsistent braking power.
Leather was eventually adopted as a braking material, providing more friction and durability than wood. Leather brake pads were commonly used in the first mass-produced automobiles in the early 1900s, such as the Ford Model T. According to the ABE Brakes article “The history of braking systems in automotive industry,” leather pads “increased the coefficient of friction between the brake drum and the pad.” However, leather pads still wore down quickly and could overheat.
Overall, these early braking systems using wooden blocks and leather pads provided only marginal braking power compared to modern systems. They required drivers to press hard on stiff brake pedals to slow vehicles. But these early mechanisms paved the way for further braking innovations using new materials like asbestos and ceramics.
Invention of Modern Brake Pads
The modern brake pad was invented in the early 1900s, with asbestos introduced as the main friction material. Asbestos had excellent heat resistance and friction properties, making it ideal for brakes. By the 1920s, nearly all brake pads contained asbestos.https://www.mesothelioma.com/asbestos-exposure/jobsites/automobiles/
However, in the 1970s, concerns emerged about the health hazards of asbestos. This led brake manufacturers to transition to new materials like semi-metallic and non-asbestos organic pads. Semi-metallic pads use fiberglass, copper fibers, iron powder, and graphite. Non-asbestos organic pads contain materials like glass, rubber, Kevlar, and carbon.https://www.asbestos.com/occupations/auto-mechanics/ While more expensive, these non-asbestos pads provided comparable braking ability without the respiratory risks.
By the 1990s, asbestos was banned in brake pads and linings in the US and European Union. The last American-made vehicles with asbestos brakes were produced in 1996. However, some aftermarket overseas brake parts can still contain asbestos today.
Brake Pad Materials Over Time
The friction material used in brake pads has evolved significantly over the years. Early brake pads were made from a variety of natural materials including cotton, wood, camel hair and leather. These materials were packed into the pads to create the friction surface.1
In the early 1900s, asbestos fibers started being used in brake pads as the friction material. Asbestos provided better heat resistance and friction compared to natural materials. Nearly all brake pads contained asbestos up until the late 20th century.2
However, due to health concerns over asbestos, brake pad manufacturers started developing asbestos-free pads in the 1970s and 80s. These used alternative friction materials like copper fibers, glass fibers, rubber compounds and metallic particles. Organic friction materials made from plant fibers also became more common.3
In the 1990s, ceramics such as zirconium and aluminium oxide started being utilized. Ceramic pads offered increased heat resistance and braking performance. More recently, brake pad materials have incorporated new high-tech compounds, nanomaterials and aramid fibers to further enhance friction and braking.
Brake Pad Design Innovations
Brake pads have gone through many design innovations over the years to improve braking performance. In the early days of drum brakes, brake pads were simple blocks of material pressed against the inside of the drum. But as braking systems advanced, engineers realized that optimizing the shape and design of brake pads could provide better grip, heat dissipation, and braking power.
One key innovation was adding curved chamfers and tapered edges to the leading and trailing edges of brake pads. This helped the pad make smooth contact with the brake disc or drum as it engaged and retracted. Slots and grooves cut into pad faces provided better cooling, debris clearing, and pad wear.
Manufacturers also began experimenting with adding a brake pad shim between the pad and caliper piston. The shim helped reduce brake noise while also evening out the pressure applied to the pad. Multi-layer shims later emerged, providing further improvements.
Today’s brake pads feature complex contours, slots, beveled edges, and thermal coatings to optimize friction, cooling, wear, and noise characteristics. Computer-aided design has enabled brake engineers to precisely shape pads for specific vehicles and applications. These innovations in pad shapes, slots, shims, and materials have drastically improved braking performance over the decades.
Rise of Disc Brakes
Disc brakes started being developed in England in the 1890s, but did not gain widespread use until the 1950s and 1960s (Golden Triangle Auto Care). Compared to the previously dominant drum brakes, disc brakes provided better stopping power, more consistent braking in wet conditions, self-cleaning ability, and better heat dissipation. Disc brakes were first used on exotic sports cars like the Jaguar C-Type in the 1950s, but by the 1970s they had become standard equipment on most passenger vehicles (Monforton & Partners LLP).
The rise of disc brakes necessitated changes in brake pad materials and design. Asbestos-based pads that were common with drum brakes could not withstand the heat generated by disc brakes. New pad materials like semi-metallic and ceramic compounds were developed. Pads also had to be designed specifically for discs, with a single pad on each side gripping the rotor. As disc brakes improved the overall braking performance of vehicles, brake pads became an increasingly important component requiring ongoing innovation.
Brake Pad Testing Standards
The development of standardized brake pad testing protocols began in the early 20th century as automobiles became more widespread. In 1920, the National Bureau of Standards (now the National Institute of Standards and Technology) started testing brake materials in the United States and developed testing equipment that was then shared with manufacturers (Wikipedia). This allowed companies to test and compare different brake pad formulations using uniform procedures.
By the 1950s and 60s, many countries began introducing mandatory safety standards for brake pads and braking systems. In the US, Federal Motor Vehicle Safety Standard 105 established specific minimum performance requirements for brakes starting in 1967. It included tests for effectiveness, fade resistance, water recovery, and other criteria (Second Chance Garage).
The introduction of rigorous, standardized brake testing paved the way for innovations in brake pad materials and designs. Manufacturers could systematically experiment with different compounds while relying on the standardized tests to provide comparable data. This enabled progressive improvements in brake pad performance over the decades.
Environmental Regulations
Starting in the early 2000s, environmental regulations began impacting the materials used in brake pads. In 2010, California passed the Brake Friction Material Law which restricted the amount of copper in brake pads to 5% by 2021 and 0.5% by 2025. The goal was to reduce the amount of copper dust produced from brake pad wear, which can contaminate waterways. Washington state passed a similar law in 2010.
These regulations spurred innovation in developing copper-free brake pads using new materials like ceramics. However, some studies found the new pads produced more brake dust overall. In response, additional regulations focused on limiting overall brake dust production through improved pad design and covering more materials beyond just copper.
Noise regulations also impacted design, as the friction material greatly affects squealing and chirping sounds. Balancing effective braking, long pad life, low dust, and quiet operation prompted more R&D investments from brake pad manufacturers. While early copper-free pads faced performance issues, companies continued improving formulations to meet the new environmental laws while maintaining safety.
Computerized Brakes and Brake Pads
As automotive technology advanced in the late 20th century, brake pads and calipers became integrated with computerized controls and sensors. In 1985, manufacturers began introducing computer-controlled anti-lock braking systems (ABS) to prevent wheels from locking up and skidding during hard braking (https://www.chicagotribune.com/news/ct-xpm-1985-04-07-8501200121-story.html).
These systems use speed sensors at each wheel, a hydraulic control unit, and an electronic control unit (ECU) to monitor wheel speeds during braking. The ECU can rapidly pulse the brake pads to prevent lockup. This allows the driver to maintain steering control while braking hard.
Modern brake pads also contain wear sensors that trip a dashboard warning light when the pad material gets low. The brake pad wear sensor is a thin wire that sits between the pad material and the backing plate. When the pad wears down, the wire eventually makes contact with the rotor and completes an electrical circuit that illuminates the warning light.
Computerized brake systems bring intelligent control and monitoring to the age-old mechanics of friction brake pads. While the basic principles remain the same, sensors and automation make brake pads safer and more efficient than ever.
Future of Brake Pads
Research into new brake pad materials and technologies aims to improve performance and reduce environmental impact in the future. Some key developments include:
New friction materials like ceramics and carbon-ceramic composites are being explored as alternatives to traditional brake pad materials. These materials can withstand higher temperatures, reduce brake fade, and improve stopping distances (The US Automotive Brake Pad Market Research Report).
Coatings and surface treatments for brake pads may help reduce noise and brake dust. Materials like graphene are being studied for their potential to create brake pads that last longer and are more resistant to water and high temperatures (The Evolution and Future of Automotive Brake Systems).
Integrated sensors in brake pads could monitor wear and communicate data to other vehicle systems, enabling predictive maintenance. Smart brake pads with built-in sensors may become more common in the future ((2023-2030) Automotive Brake Pads Market Challenges).
As more electric vehicles are produced, low-copper and copper-free brake pads will be needed to avoid shorting electric motor rotors. Expect ongoing innovation in materials as brake pads adapt to changes in vehicle technologies.