Game Changer: Disc brakes

Any kid who has ridden a bike with rubber blocks that grip the wheel rim to (eventually) bring you to a shuddering stop will understand the science and simplicity of disc brake design.

Those same kids might also have wondered, as their first car was cooking its drum brakes, why it took so long before brake discs – also known as rotors – were adopted for automotive use.

The automotive disc brake was indeed based on the principle of bicycle brakes and trialled by an American inventor before being fitted in 1902 to a British car.

Lanchester was at the time a fledgling concern and likely didn’t have the money to properly develop the concept. Another UK inventor took on the task and in 1905 replaced the copper in Lanchester’s brake pads with heat-resistant asbestos.

Progress then slowed and little use was made until the 1920s when Douglas adopted the braking system for some of its motorcycles. However, car makers remained reluctant.

As pneumatic tyres gained popularity, a braking system that didn’t act directly on the face of a metal rim or solid tyre was important. The drum brake enclosed all of its working parts within the cast iron drum, ensuring they were protected against dirt, damage and water.

For decades after the concept appeared, car-makers felt that discs with their exposed pads would suffer accelerated wear and that mud or water on the rotor would make them less efficient than a drum system.

Heat dissipation wasn’t seen as an issue at a time when vehicle speeds were moderate and retained heat helped the drums work better.

Aeronautical designers during World War II toyed with the idea of disc braking for heavy aircraft but it took a decade after the war’s end for a reliable system to become available.

US manufacturers were the first during the late 1940s to dabble in disc braking for motor vehicles, but technical issues dissuaded Crosley and Chrysler from getting too involved in development of disc-braked models.

Jaguar won the 1953 Le Mans 24 Hour race with a team of disc-braked C-Types, while Austin-Healey was the first to fit all-wheel discs to a production sports car.

By 1959, Jaguar was fitting all-disc braking systems across its range of sports and saloon cars, as was Aston Martin.

Triumph with its TR3 and Jensen were other early-adopters, but others seemed reluctant to follow the lead of Citroen, which from 1955 had fitted inboard front discs to its DS sedan.

Mercedes-Benz and Volvo were among the brands that took until at least 1961 before adding disc brakes to some production models. By that time, MG had installed front discs on its MGA, Rover had them on its 3.0-litre and was preparing to go all-disc with its new 2000 sedan.

Australia was one of the last bastions of the drum brake, holding out until 1965 when Ford introduced its XP Fairmont with front discs as standard.

Still, the preference for drums continued and not until the late 1970s did mainstream Australian models have discs on at least their front wheels.

Had it survived, Ford’s Falcon GTHO Phase IV would in 1972 have been the first Australian production sedan with four-wheel disc brakes. Instead, we needed to wait until the end of 1973 for the XB Falcon GT to flatten that remaining barrier.

By 1978, Holden was offering an all-disc system on its full-size cars and the high-performance Torana A9X. But again, it would still take many years for its entry-level Australian model to routinely adopt all-disc brakes.

Today, disc brakes are employed almost exclusively across the automotive industry, except for a number of entry-level, battery-electric and commercial vehicles that employ drum rear brakes in at least some variants.

These include the Cupra Born, Fiat 500e, Mazda2, MG3, Suzuki Baleno and several of Volkswagen’s upcoming ID EV models, plus the top-selling Toyota HiLux, Isuzu D-MAX, Mazda BT-50, Nissan Navara and Mitsubishi Triton (including the upcoming sixth generation).