Hitting the Brakes: A History of Automotive Brakes
By Llewellyn Hedgbeth
Starting cars with a hand-crank was never easy and bringing them to a halt wasn't a cake walk, either. Many early cars used simple "spoon" brakes like carriages had: a driver relied on a lever system that moved a block of wood against the wheels. These worked relatively well for speeds of 10-20 mph in sparse traffic. By the late 1890s, though, when the Michelin brothers came out with rubber pneumatic tires, the wood block idea was pretty useless because the wood ground the rubber down pretty badly.
In 1898, an enterprising inventor from Cleveland, Elmer Ambrose Sperry, designed an electric car with front-wheel disc brakes, built by the Cleveland Machine Screw Co. With disc brakes, a caliper with brake pads pinches a rotor or disc—like bicycle brakes. The man credited with the invention of the disc brake, however, was English engineer Frederick William Lanchester who patented the idea in 1902. The biggest problem with his brakes, though, because copper brake pad linings moved against a metal disc, was the horrible screeching noise they made. It took another five years for someone else to cure the noise problem: Herbert Frood, a fellow Brit, lined the pads with long-lasting asbestos. In fact, asbestos continued to be used in car brakes until the 1980s when health and safety concerns eliminated it. Still, the disc brake didn't enjoy much popularity. It wasn't until the 50s that European cars began the wide use of disc brakes. In 1967, Federal Motor Vehicle Safety Standard 105 set specific performance tests that led to the widespread introduction of disc brakes on American cars in the early seventies. But we'll leave the disc brakes for now and focus instead on the later-introduced but, initially, more popular drum brakes.
Mechanical Drum Brakes
The first, or among the first, to wrap a cable around a drum anchored to the vehicle's chassis—the basic idea for drum brakes—was Gottlieb Daimler, in 1899. Wilhelm Maybach, designer of the first Mercedes, utilized rudimentary, mechanical drum brakes in 1901. These were steel cables wrapped around the drums of the rear wheels and operated by a hand lever. Louis Renault, however, is the man credited with the 1902 invention of the drum brake which would become standard for automobiles. In drum brakes, brake shoes generate friction by rubbing against the inner surface of a brake drum attached to a wheel. There are external-contracting brakes in which the brake band surrounds the drum and internal-expanding drum brakes in which the shoes, supported by a back plate, are forced outward against the drum.
In the U.S., one of the first to manufacture drum brakes was the A. H. Raymond Co. of Bridgeport, Connecticut, opened in 1902 as a four-man shop that built brakes, brake linings, and clutch facings. Re-named Royal Equipment Co. by 1904, the company continued to improve brakes, particularly with an asbestos and copper-wire brake lining known as "Raybestos". The claims the Raymond Co. could make were that it had "double acting" brakes—stopping both forward and backward motion and that the driver could now choose to stop suddenly or gradually.
In 1902, Ransom E. Olds of Oldsmobile tested an early external-contracting brake design during a race on Riverside Drive in New York City. The design called for wrapping a flexible stainless steel band around the rear axle drum. The driver depressed the foot pedal mounted on the floor to operate the brake band which gripped the drum. Olds was pitting his car's braking power against that of a tire brake (a pad applied to the tire by means of a long lever) for a four-horse coach and an internal drum, expanding-shoe design for a Victoria horseless carriage. Stopping from a speed of 14 mph, the horse-drawn carriage (which may not really have gone as fast as the cars) stopped in 77.5 feet, the Victoria in 37 feet, and the Olds in 21.5 feet. The results were impressive enough that by 1903 many manufacturers were using the Olds brake design and by 1904 virtually all manufacturers had gone to the external brake on each rear wheel.
There were some notable drawbacks with external brakes, though. At times, while on hills, the brake could come unwrapped and give way, sending the car rolling backward. Drivers could remedy that problem by getting a passenger to jump out and wedge a wooden chock beneath the rear wheel. Also, because the brakes were exposed to the elements, they didn't last long and required frequent replacement. Brakes slipped in wet weather and daily dirt and grime wore them away. Consider how you might like having to have your brakes replaced every couple of hundred miles. It didn't take long for manufacturers to return to internal-expanding drum brakes. Internal brake shoes, under pressure, stayed against the drums, preventing cars atop hills from rolling backward. And because the parts were internal, brakes could last 1,000 miles or more.
As speeds—and traffic—increased, manufacturers began to look for improvements. One arose in 1915 with the Duesenberg entered in the Elgin Road Race (sponsored by the Elgin Watch Company). With the innovation of applying internal brakes to both front and rear wheels, its driver could reach 80 mph on the straightaway, then brake to a much slower speed to go round the tight curves. In 1919, the French-made Hispano-Suiza H6B utilized a single foot pedal to operate the coupled four-wheel brakes, a departure from the common requirement that a driver had to apply a separate hand and foot brake simultaneously. At the 1924 New York Auto Show, only Duesenberg and Rickenbacker offered four-wheel brakes. In late 1923, Chalmers offered them as an option priced at $75—and Buick, Cadillac, Chrysler, and others fell in line with four-wheel brakes soon thereafter. While competitors that did not offer them made the claim that these brakes were unsafe, they were definitely here to stay. By the 1980s, most cars came with four-wheel drive disc brakes.
Another improvement came about in 1918 when Malcolm Lougheed (later changing his name to Lockheed, of aviation fame) invented a hydraulic braking system. Mechanical brakes, besides requiring drivers to exert significant force on the brake pedal, did not brake all wheels evenly, sometimes leading to loss of control. Using cylinders and tubes, Lockheed sent fluid pressure against brake shoes, pushing them against the drums. It required much less exertion for the driver to apply these brakes. The hydraulic system was a definite improvement and the avant garde 1921 Model A Duesenberg was the first production car to use four-wheel hydraulic brakes. It was followed by Chalmers cars in late 1923. Walter Chrysler had been brought aboard at Chalmers to improve its financial picture—but the company foundered shortly thereafter nonetheless. In 1924, he was leading Chrysler in its first year and using four-wheel hydraulic brakes that were based on the Lockheed principle but completely redesigned. The original Lockheed brakes leaked badly, in large part because of the use of rawhide cup seals to contain the hydraulic fluid. Because the rawhide dried up and shrank over time, Chrysler replaced them with rubber cup seals. Lockheed appreciated the improvement and OK'd Chrysler to use his design royalty-free—so long as he could also add the improvement to the original patented Lockheed design. The new brake type, known as Chrysler-Lockheed hydraulic brakes, were ones Chrysler utilized from 1924 to 1962.
Other car manufacturers followed suit. In 1924, the Hupmobile Straight-8 came with four-wheel hydraulic brakes, while the Six still had mechanical brakes. Stutz, in 1926, was using hydrostatic brakes with six bladders replacing brake shoes, a system that lasted only a year before Stutz licensed Lockheed hydraulic brakes. The hydrostatic brakes worked OK but the water in the system froze up during cold winters. There were definite advantages to the hydraulic brakes but few manufacturers—among them Dodge, Desoto, Auburn, Graham, and Plymouth—were using them by 1931.
But GM and Ford still utilized mechanical brakes. It wasn't until the mid-30s, in fact, that GM went to Bendix hydraulic brakes. Vincent Bendix, after meeting French engineer Henri Perrot at a European auto show in 1924, acquired the license to make mechanical shoe-brakes and took over Perrot's contract to supply brakes to GM. With design improvements, Bendix offered a four-wheel drive mechanical braking system but contention was sharp as to whether mechanical or hydraulic brakes were better. Bendix, figuring no one needed fluids leaking out onto the garage floor, favored reliable mechanical brakes. Lockheed, however, claimed that hydraulics meant less skidding and were, overall, much safer than mechanical brakes. As more manufacturers chose hydraulic brakes over mechanical ones, Bendix eventually purchased Lockheed's Hydraulic Brake co. in 1930, and in the mid-30's GM switched to hydraulic brakes for all its cars.
No hydraulics for Ford in the '30s
When the Ford Model A was being designed, Edsel Ford equipped them with hydraulics. When his father Henry Ford test drove one, however, the luck of the draw applied. He got a car that had been tested previously and had a cracked line — so the brakes didn't hold. Hydraulic brakes were out at Ford— at least until the early 1940's.
While Ford acknowledged there was a need for brakes, he didn't think there was a need for anything fancy. The Model T, which arrived in 1908, had service brakes applied to a drum inside the transmission—and Ford used these mechanical brakes through 1938. Ford was, in fact, the last auto manufacturer to switch to hydraulics.
Brake Assist (Power Brakes)
Some early innovations with brakes now seem way ahead of their times. Brake assist, for instance, was first made available in 1903 with the Chicago-based Tincher. A small pump compressed air to stop the car, or, if you wanted, the same pump could inflate the tires or toot the whistle. The 1928 Pierce-Arrow was the first production car, however, to come with a vacuum-operated power booster for brakes, the Bragg-Kliesrath. Caleb Bragg and Victor Kliesrath, in the mid-20's, had invented the vacuum-assisted brake booster for the aeronautics industry. The intake manifold supplied the vacuum needed to reduce the amount of effort required to apply the brakes. Chandler cars, from 1927-29, came with a Westinghouse Vacuum Booster, and by the early 30s, Lincoln, Cadillac, Duesenberg, Stutz, and Mercedes were also including vacuum- assisted drum brakes. Drum brakes remained standard, however, because they worked well and were cheaper to manufacture than disc brakes.
Beginning in the 40s other power-assist systems began to appear, and by the 50's power brakes were common. Systems such as the Hydrovac, the Hydroboost, and the Treadle-Vac (known as the Easamatic on '52-'56 Packards) came factory-installed. In the Hydrovac system, when the driver pressed the brake pedal, fluid pressure was increased to a slave cylinder and the wheel cylinders. More pressure activated a valve that, in turn, activated a triangular arm. The arm rotated valves to close an atmospheric valve and open a vacuum valve, pulling vacuum air into a large chamber and pushing a bellows against a valve in the slave cylinder to increase fluid pressure to the wheels. It was a real Rube Goldberg system but it worked.
The Hydroboost system, rather than using a vacuum, relied on power generated by the power steering pump. The Bendix power booster was the Treadle-Vac, mounted on the floorboard right under the brake pedal and available on all GM cars in the 50s as well as on Edsel, Lincoln, Mercury, Hudson, Nash, and Mercedes models. The Treadle-Vac was a single line system, however, which meant that a failure of any hose or joint could impair the entire system. In 1959, the Delco-Moraine power booster mounted high on the firewall became the system of choice instead. All these systems meant that the driver no longer need stand on the brakes to stop the car. With far less pressure, the car could be brought to a halt.
There were also early self-adjusting brakes. The 1925 Cole, in its last year of production, had them. They would not appear again until 1946 when Studebaker used a Wagner Electric Co. mechanism. As the linings wore down, a pin and lever moved against a tension spring, engaging the adjusting wedge which moved the linings slightly and kept them at the same distance from the drums. Self-adjusting brakes showed up on the '57 Mercury and the '58 Edsel and were recommended to purchasers anxious to avoid frequent and costly brake adjustments. By the mid-60s, AMC was offering self-adjusting brakes, as well.
Antilock (antiskid) brakes (ABS) are not entirely new, either. They are a safety feature which prevents the wheels from locking while braking. If speed sensors detect that a wheel is about to lock up, a series of hydraulic valves reduces braking on that wheel, preventing a car from going into a spin. Gabriel Voisin, a French pioneer in aeronautical and automotive engineering, introduced them in 1929 for airplanes. By 1936, Bosch and Mercedes-Benz had an electronic ABS for the Mercedes. It wasn't until 1958, however, that a practical ABS was developed for cars: Maxaret was developed in Great Britain and used in the Jensen FF sports sedan in 1966. The Ford Zodiac in the 60's experimented with ABS for all-wheel drive but the ABS was very expensive to produce. Then, in 1969, Ford brought out the Lincoln Continental Mark III and the Thunderbird with "Sure-Track", a Kelsey-Hayes Auto-Linear antilock unit in which wheel sensors transmitted data to a transistorized computer set behind the glove box. The system controlled only the rear wheels, there were some technical problems with the system and, again, the production costs were very high.
In 1971, Chrysler introduced the first reliable ABS with its Bendix "Sure Brake" system on the Chrysler Imperial. That same year, GM offered an ABS "Trackmaster" as an option on its rear-wheel drive Cadillacs. Ford stayed the course and, in 1975, included its "Sure Trak" on the Lincoln Continental Mark II and the LTD station wagon. In the 80's, Ford also had an electronic, 4-channel ABS on the Lincoln Continental Mark VII (1984) and utilized a Kelsey-Hayes rear-wheel ABS on its F series trucks (1987).
A real step forward for ABS, however, came when Bosch and Mercedes-Benz developed an updated system for the Mercedes S-Class in 1978. A significant refinement on their original 1936 system, it was a completely electronic, four-wheel, multi-channel system. Other companies soon built on this model and today most cars, regardless of their price class, are fitted with ABS. In 2006, Mercedes unveiled a further update with its Brake Distronic Plus system. Using long-and short-range radar, it can bring the car to a stop even if the driver does not touch the brake pedal—no more rear-end collisions.
Now, back to disc brakes. There were some problems with drum brakes right from the beginning. Heat builds up with them and, over time, the brake can warp, causing vibrations. Disc brakes, on the other hand, wear longer, are self-adjusting and self-cleaning, less prone to grabbing or pulling, and stop better, too.
In 1949, Crosley utilized disc brakes on its Hotshot (though they had to be replaced about once a year) and Chrysler fitted disc brakes on their Town & Country and Imperial models, an innovation which continued through 1954. The Chrysler brakes, built by Auto Specialists Manufacturing Company (Ausco) based on a design by H. L. Lambert, used twin discs that spread apart and rubbed against the interior of a cast-iron drum. These brakes required less pedal pressure than caliper discs and provided more friction surface than drum brakes—but they were expensive to produce. You could order them added to other Chrysler vehicles at a cost of $400 but that was a lot of money back them and few buyers asked for them. Even when they did, they found that they had to exert a good bit of pressure to the brake pedal to bring the car to a stop.
Bendix made a break-through in brakes in 1962 when it supplied four-wheel disc brakes for the high performance Studebaker Avanti. The introduction was a success—in part because this system assisted the piston in the master cylinder to move, meaning the driver had to exert less pedal pressure. Until then, drivers saw better braking action from drum brakes since they had self-energizing capacity, i.e., the forward motion of the car helped pull the brake shoe into contact with the drum. In 1964, Studebaker introduced disc brakes to all its models and it took only a few years for these improved disc brakes to appear in many other new cars. It was a good thing, too, since the size and horsepower of cars had increased and drum brakes could no longer meet the increased demands.
Dual Master Cylinders
Throughout the early years, there was a single Master Cylinder reservoir that pumped through a junction block to lines and hoses, distributing fluid to each wheel. The only real problem came if any portion of the system failed or leaked. Then pressure wouldn't build up anywhere within the system—and the brakes stopped working.
In 1960, Wagner Electric (later acquired by Studebaker) developed and filed a patent for a dual-cylinder brake system. Two years later Cadillac introduced a new braking system with a dual master cylinder and separate front and rear hydraulic lines so that if one circuit had a leak, the other could still stop the car—and AMC also offered the tandem cylinders as standard equipment. Studebaker joined them in 1963.
The federal government stepped in, too; in 1967, it mandated the use of dual-braking master cylinders. A 1983 NHTSA report calculated that the feature prevented 40,000 accidents each year.
Coming Soon to a Car Dealer Near You
Automotive companies are experimenting with full contact disc brakes which increase the contact between the surface of rotors and brake pads from 15% to 75%. Siemens has a "green" electronic wedge brake that takes less power, just that of a car's simple 12-volt power system—and achieves a significant reduction in braking distance, not an unimportant feature in emergency conditions. Whatever additional braking improvements are just round the bend, you can bet that braking systems will be more compact and more efficient with faster response times.