Asbestos Brake Lining

Asbestos brake linings are curved friction strips designed to press against the inner surface of a brake drum when the brake is applied. They were among the earliest and most prolific uses of asbestos in the automotive industry, dating back to the late 1910s when drum brakes became standard on production vehicles. Chrysotile asbestos fibres, typically constituting 40 to 70 percent of the lining by weight, were woven or moulded with phenolic resins, metal powders, and friction modifiers to produce a material that could withstand temperatures exceeding 300 degrees Celsius without significant fade.

Drum brake systems equipped with asbestos linings were used on virtually every make and model of car, truck, bus, and heavy equipment worldwide throughout the twentieth century. Manufacturers such as Ferodo, Bendix, Don, and Mintex were the dominant suppliers. The linings were either bonded directly to the brake shoe or riveted in place, with riveted designs allowing easier replacement.

The health hazard from brake linings mirrors that of brake pads but is amplified by the enclosed drum design. Brake drums trap wear debris inside the assembly, accumulating large quantities of asbestos-laden dust over thousands of kilometres. When a mechanic removed a drum for inspection or lining replacement, the accumulated dust was often blown out with compressed air, creating intense fibre exposure. This blow-out practice, routine in workshops from the 1920s through the 1980s, is now recognised as one of the most significant occupational exposure routes for automotive workers.

Epidemiological studies have documented excess mesothelioma mortality among brake mechanics, with the risk proportional to years of service and the era in which they worked. When new, brake linings are non-friable because the asbestos is bound in resin. Through wear, heat cycling, and eventual replacement, the material becomes increasingly friable, releasing fibres readily when handled or disturbed.

While most developed nations banned asbestos friction products by the early 2000s, countries such as India, Russia, and several Southeast Asian nations continued to permit their manufacture and use. The United States likewise never fully banned asbestos brake linings.