Asbestos Brakes, Clutches, and Friction Materials

For most of the twentieth century, the friction surfaces that stopped America's cars, trucks, buses, and trains were made of asbestos, and the mechanics who serviced them worked in the dust those materials shed. Blowing out a brake drum with compressed air, the most routine gesture in the trade, was measured at 43.8 fibers per cubic centimeter in EPA-commissioned testing, which in fifteen minutes puts roughly twelve years' worth of ordinary city background air through a mechanic's lungs¹, and the friction industry was recording meaningful fiber releases in its own facilities while its trade literature told mechanics the dust was harmless. You don't need to remember which brand of lining you installed or dig up decades-old repair orders to find out whether you have a claim; if you did brake or clutch work, that's where we start.

Even ordinary city air carries a faint trace of asbestos everywhere, from natural mineral erosion and decades of industrial use, and that trace is the baseline both sides of the panel are measured against. The panel shows one well-documented measurement of the air-blow task; other studies measured the same task lower, and the honest study spread is laid out in the exposure table below.

What these numbers mean. Asbestos in air is measured in fibers per cubic centimeter (f/cc), a unit that hides how dangerous a task was. Across this site we translate each measurement into fibers breathed, feet of fiber end to end, and years of ordinary city air, using conservative, government-sourced assumptions. See how we measure asbestos in air for the method and its limits.

What asbestos friction materials were

A brake lining is the friction surface that presses against a drum or rotor to stop a vehicle; a clutch facing is the matching surface that lets an engine engage a transmission. Both jobs demand a material that grips hard, holds together under repeated heating, and doesn't wear away in a week, and for most of the twentieth century that material was asbestos, specifically chrysotile (white asbestos, the serpentine mineral that made up nearly all friction material). The fiber was bound into the part with a phenolic resin or rubber binder and packed with metallic and mineral fillers for strength and heat resistance, and across the whole category the finished product ran roughly 40 to 60 percent chrysotile by weight.

Friction products came in four families. They shared that same basic recipe, but differed in shape, in how much heat and load they had to take, and in how the part was installed and later pulled back out, which is what shaped the exposure.

Brake linings and pads were the largest family by far, both in how much asbestos they used and in how much exposure they generated, and they're the ones most workers picture: the molded or woven lining riveted or bonded to the curved steel shoe of a drum brake, and the disc pad with its steel backing plate. They stopped passenger cars, trucks, and buses, and the work of fitting and replacing them, especially grinding and beveling a new lining so it seats flush, is behind most of the documented brake-shop exposure.

Clutch facings were the next largest family, rings of woven or molded friction material (sometimes reinforced with brass or copper wire) on the clutch disc of a manual-transmission vehicle, opened to the air every time a clutch was serviced.

Automatic transmissions used their own asbestos bands and friction discs, which ran wet in transmission fluid inside the housing but still released fiber when the unit was torn down and rebuilt.

And a whole industrial family sat outside consumer vehicles entirely: the oversized brakes and clutches on elevators, cranes, forklifts, and mill equipment, built to hold or stop far heavier loads, where a single elevator brake lining might hold the weight of a full car and everyone riding in it.

Representative products and their asbestos content. These are examples, not a full list:

Friction material was almost always a chrysotile product. Outside of a few rare niche products, there's no hidden amphibole (the other asbestos family, generally considered more hazardous) story here. But although chrysotile itself is less likely to cause mesothelioma than other forms of asbestos, it has been classified by the International Agency for Research on Cancer as carcinogenic to humans and recognized as a cause of mesothelioma⁸. The defenses built around the chrysotile point are taken up, carefully, in the defenses section below.

Play the film from 7:00: Asbestos: Where It Came From and Where It Is Used from 7:00

How friction materials put asbestos in the air

An asbestos brake lining bolted to a shoe and sitting inside a drum isn't shedding much fiber into anyone's breathing zone. The exposure came from servicing it. Brake and clutch work was abrasive by design: new linings were ground, filed, and beveled to fit the drum; clutch facings were sanded true; and every drum-brake job began by getting the accumulated dust out of the drum, which for decades meant an air hose. Grinding, filing, and sanding release raw, friable (crumbly and easily airborne) chrysotile from the new lining, and blowing out a drum throws the accumulated wear dust into a cloud around the mechanic's face.

Here is what that work measured. Each figure is a phase-contrast (PCM) measurement, which counts only the longer fibers and so reads as a floor, not a ceiling:

By the illustrative math on our how we measure asbestos in air page, 15 minutes of blowing out brake drums at the GCA figure put roughly 12 years of ordinary city air through the lungs. This estimates fibers in the air breathed, not a retained dose.

Two honest caveats: First, in routine brake changes the parts of the job that weren't grinding, sanding, or air-blowing, measured lower than the abrasive tasks in the table. Second, the same air-blow task was measured very differently across studies: the EPA-commissioned GCA work recorded 43.8 f/cc, while a Finnish study of routine compressed-air cleaning recorded about 1.5 f/cc⁶. Study conditions, drum contents, and technique varied, and we present the spread rather than pretend all exposures were always high. What no study disputes is that the abrasive work released chrysotile fiber into the mechanic's breathing zone, and the arbor-sanding measurements show how extreme the upper end could be.

What the makers knew

The friction industry was not guessing about its dust. Through the 1970s, the makers' own hygienists and independent researchers were measuring fiber release from friction materials and friction work, while the trade press and service literature told mechanics the dust was nothing to worry about.

Abex measured its own plant. The Abex Corporation's industrial hygienists sampled the air in its Salisbury, North Carolina friction-manufacturing plant in 1976, documenting the company's direct, dated knowledge of airborne fiber from its own product line⁵. The next year, researchers from Mount Sinai led by Arthur Rohl took independent breathing-zone (the air right at a worker's nose and mouth) measurements in working American brake shops, putting the hazard on the public scientific record in 1977⁴.

The work-practice studies that followed confirmed what the mechanics had been breathing all along. A 1998 Materials Analytical Services study of Bendix brake-lining filing on Chrysler vehicles recorded breathing-zone air at about 8 f/cc², and a companion MAS simulation of sanding a Borg-Warner clutch plate on an arbor recorded an astounding 385 to 466 f/cc³, some of the highest task measurements in the friction literature.

Who was exposed

Friction materials weren't confined to one trade, but the exposure ran through a recognizable set of workplaces and occupations:

• auto and brake mechanics, the primary trade, from dealership service bays to corner garages and gas stations
• railroad shops, where locomotive and car brake shoes meant heavy asbestos brake blocks
• aircraft maintenance, where wheel and brake work carried the same friction-material dust

If you or your family member did brake or clutch work in any of these settings, the exposure history is usually straightforward to reconstruct.

The manufacturers and the trusts

Brake and clutch recovery runs down two tracks at once, and this category is unusual in how strong the second track is. The bankrupt makers now pay through trusts that require no lawsuit. But one of the biggest names in friction, Bendix, never went bankrupt: its successor Honeywell is a solvent company that defends these cases in court, and Ford and other still-solvent automakers and friction sellers can likewise be sued directly. A single mechanic's career often supports trust claims and lawsuits at the same time, and one pathway doesn't reduce another.

A note on the Raybestos name, because it was on half the parts shelves in America: the corporate successor, Raymark, went through a Chapter 7 liquidation which means they went out of business entirely. That's different than the typical reorganizations that create a trust, so recovery on that name runs differently and is more limited. How a particular defendant is reached, and whether a successor company answers for an older one, is analysis we do for your file, not something you need to sort out. And if the idea of a lawsuit is uncomfortable, you're in good company; Clarence Borel, whose 1973 case built the modern asbestos-litigation system, didn't want to sue either, and we can pursue trust claims alone if that's your preference.

Sources of compensation

A brake and clutch case usually draws from several sources at once, and they run in parallel:

• Asbestos bankruptcy trusts. The friction makers who went bankrupt set aside money to pay the people they harmed. These are paper claims, with no lawsuit and no courtroom, and one career often supports filings against several trusts. How asbestos trust claims work.
• Lawsuits against solvent defendants. Honeywell (for Bendix), Ford, and other still-solvent automakers and friction sellers defend these cases in court, and those tort recoveries often exceed what trusts pay per claim. How product liability lawsuits work.
• Premises liability against site owners. Where the brake work happened on someone else's site, a fleet garage, a plant, a facility that controlled the conditions, the owner can sometimes be reached as a premises defendant. How premises liability claims work.
• Federal and disability benefits. Military vehicle and aircraft brake work can support VA disability benefits, and Social Security disability may be available alongside any claim, both paid in addition to the rest. How asbestos disability and benefit claims work.

Friction cases draw a more scientific set of defenses than most asbestos products, because the defense bar has spent decades building arguments around chrysotile. None of them is new to us, and each deserves a precise answer rather than a slogan. All of this applies only to the lawsuit side. Trust claims are a paper process: no opposing lawyer raises defenses, no one is deposed, and no one goes to court.