Asbestos was used in brake pads because it could withstand extreme heat without breaking down, provided consistent friction for stopping power, and was cheap to mine in large quantities. For most of the 20th century, no other material came close to matching that combination of properties, making asbestos the default choice for automotive friction products from the 1930s through the mid-1980s.
The Properties That Made Asbestos Ideal
Braking generates intense heat. Every time you press the brake pedal, kinetic energy converts to thermal energy at the pad surface, and temperatures can spike to several hundred degrees in normal driving. Asbestos fibers, particularly the chrysotile variety used in most brake products, don’t begin to break down until temperatures reach 700 to 800°C. That thermal stability meant brake pads could endure repeated hard stops without degrading or losing grip.
Beyond heat resistance, asbestos delivered a friction coefficient of 0.3 to 0.4, which sits in the sweet spot for braking: high enough to stop a vehicle effectively, low enough to avoid grabbing or locking the wheels. The wear rate was also remarkably low at 3.8 milligrams per meter of contact, meaning pads lasted a long time before needing replacement. Asbestos fibers are also naturally flexible and can be woven or pressed into composite materials alongside resins and fillers, making manufacturing straightforward.
On top of all that, asbestos is a mineral mined directly from the earth. It was abundant, inexpensive, and required relatively little processing to turn into a usable industrial fiber. For manufacturers trying to produce millions of brake pads at scale, the economics were hard to argue with.
How Long the Industry Relied on It
Asbestos dominated the brake industry for roughly five decades. By the 1930s, it had become the standard reinforcing fiber in brake linings, and it held that position through the 1970s with virtually no competition. The material wasn’t just common; it was everywhere. Brake pads, clutch facings, drum brake shoes, and various other vehicle friction components all contained substantial amounts of chrysotile asbestos.
The first serious pressure to change came in the 1970s, when the International Agency for Research on Cancer identified all major types of asbestos as cancer-causing agents, with particular concern about mesothelioma. The friction materials industry was well aware of the risks. Internal communications from industry trade groups acknowledged that chrysotile’s association with mesothelioma and other cancers was “of serious concern,” and published research warned that brake repair workers in garages and service stations faced elevated cancer risk from asbestos dust released during routine maintenance.
Despite those warnings, the transition away from asbestos was slow. Asbestos-containing brake products were functionally removed from new vehicle manufacturing in the United States by 1985, but aftermarket parts containing asbestos persisted for decades longer.
The Health Problem With Brake Dust
The same fibrous structure that made asbestos so effective in brake pads also made it dangerous. When brake pads wear down, they shed fine dust. With asbestos pads, that dust contained microscopic fibers that could be inhaled deeply into the lungs. The fibers are too small and too durable for the body to break down or expel, so they lodge permanently in lung tissue and the lining of the chest cavity.
Mechanics were the most directly affected. Blowing out brake drums with compressed air, a common shop practice for decades, could send clouds of asbestos fibers into the air. OSHA eventually set a permissible exposure limit of 0.1 fiber per cubic centimeter of air, averaged over an eight-hour workday, and required specific engineering controls like wet wiping or enclosed vacuum systems to keep exposure below that threshold. But many workers had already spent years breathing in brake dust with no protection at all.
What Replaced Asbestos in Brake Pads
Finding a replacement took real effort because no single material replicated everything asbestos did. The industry eventually settled on three main categories of asbestos-free brake pads, each with trade-offs.
- Semi-metallic pads use steel fibers, iron powder, and other metals mixed with fillers and resin. They handle heat well and provide strong stopping power, especially under heavy braking. The downside is more noise and faster wear on brake rotors.
- Ceramic pads use ceramic fibers and compounds that produce less dust and operate more quietly. They perform consistently across a wide temperature range and are gentle on rotors, making them popular for everyday passenger vehicles.
- Organic (NAO) pads use fibers from materials like glass, rubber, carbon, and Kevlar bound with resin. They’re the softest and quietest option but tend to wear faster and don’t handle extreme heat as well as the other two types.
All three alternatives meet or exceed the braking performance of the old asbestos formulations for normal driving conditions. The friction coefficients and wear characteristics have been refined over decades of development to the point where asbestos offers no practical advantage.
When Asbestos Brake Pads Were Finally Banned
The United States didn’t fully close the door on asbestos in brake products until 2024. Under a final rule from the Environmental Protection Agency, effective November 25, 2024, all manufacturing, importing, processing, and distribution of chrysotile asbestos aftermarket brake pads and linings is prohibited. That applies to both commercial and consumer sales.
There is one exception: brake pads already installed on vehicles before the cutoff date can remain in use. They aren’t required to be removed. The EPA’s approach is to cut off the supply chain so that asbestos-containing pads gradually disappear as they wear out or the vehicles they’re on are retired. For anyone still driving an older vehicle with original-era brake components, this means the pads you have can stay, but you won’t be able to buy asbestos replacements when they wear down.
The nearly 40-year gap between the industry’s voluntary shift away from asbestos in the mid-1980s and a formal federal ban reflects how long aftermarket and imported asbestos brake products continued to circulate, particularly for vintage vehicles and heavy equipment where older formulations were still in demand.