Despite the improvements, disc brakes were still not as reliable and were considered too expensive to be an affordable upgrade. It would be another 20 years, at the end of the muscle car era, before disc brakes became standard equipment from manufacturers.
European cars were widely using disc brakes in the late 1950s, but American manufacturers were pushed into disc brake technology with 1967’s Federal Motor Vehicle Safety Standard that set the stage for disc brakes on American cars. Disc brakes would wait, but the traditional drum brake technology continued to evolve.
Power-Assist Brakes and Self-Adjusting Brakes
Unbelievably, the first brake assist appeared in the Tincher automobile made in Chicago in 1903. The system employed a small compressor pump that helped stop the car, inflate tires if needed, and sound the whistle horn. Pierce-Arrow produced the 1928 models with a vacuum-operated power brake booster, borrowing from the aviation industry for its production car.
Other power-assist brake systems appeared here and there over the years, but after the war, power brakes were commonplace. Various vacuum systems were available through the 1950s from various manufacturers, including Bendix. The Bendix system was available on all GM cars but could also be found on Edsel, Lincoln, Mercury, Nash, and a few other brands. The Delco power booster system eventually took over as the system of choice at the end of the decade. A firewall-mounted power booster provided a true power assist, allowing the car to be smoothly brought to a stop without excessive pressure. This is the basis for power-assist systems still used today.
CPP’s HydraStop system is a hydraulic brake assist system designed to upgrade manual or vacuum-assisted brakes with a compact hydraulic assist unit. This is especially helpful when engine vacuum is low and traditional power assist won’t work correctly. (Illustration Courtesy Classic Performance Products Inc.)
The CPP HydraStop unit comes in a few different styles, but this Street Beast version is the most popular. The unit uses fluid pressure from the power steering system to assist in applying pressure to the master cylinder.
The main component in the self-adjusting brake system is the self-adjusting screw. The adjusting screw is basically a threaded device that extends and contracts. The head of the adjustment screw is a notched wheel with a cylindrical pin. The pin is capped with a washer and a slotted cap on each end. The slots fit into the brake shoes to add pressure as needed due to friction pad wear.
Much like the power-assist brakes, self-adjusting brakes existed almost as early as drum brakes but not as frequently through the decades. First appearing on the 1925 Cole, the Indianapolis-based company specialized in luxury cars, but the 1925 model would be its last. Self-adjusting brakes would not return until after the war when Studebaker adapted a Wagner Electric unit to its cars. Slow to catch on, the self-adjusting drum brakes continued to be fitted to more vehicles in the 1960s.
Antilock Brakes
Antilock brake systems (ABS) may sound more like a modern invention, but nothing could be further from the truth. French aviation pioneer Gabriel Voisin, the creator of Europe’s first engine-powered airplane and major manufacturer of military aircraft, developed the first antilock brakes.
Voisin became a manufacturer of luxury cars later in his career with a company he called Avions Voisin. Voisin first used the antilock brakes on aircraft in 1929. They were introduced in his automobiles shortly thereafter.
Mercedes-Benz debuted an electronic ABS in 1936, and the British Jensen sports cars used a similar basic electronic ABS in 1966. Other car manufacturers experimented with antilock systems with varied success until Ford hit upon the Sure-Track system in 1969 for the Thunderbird and Lincoln Mark III models. These systems were a Kelsey-Hayes antilock unit that included wheel sensors on each wheel that transmitted reference signals to a computer in the dash panel. There were some problems with the system, and it only controlled the rear wheels, but the theory was in place.
Chrysler and General Motors both offered ABS in 1971 as options. Ford joined the club in 1975 as options on its Lincoln Continental Mark II and the LTD Station Wagon. Antilock brakes became commonplace in the late 1990s, and even work trucks were fitted with these handy safety devices. Modern vehicles use ABS integrated with long- and short-range radar that can bring a car to a stop even if the driver doesn’t activate the brake pedal.
Theory of Braking Systems
Until the turn of the century, brake systems have not received the accolades that many of the other systems in automotive manufacturing have. Engines, transmissions, rear ends, wheels and tires, along with electrical and ignition systems have all earned their place in the limelight over the past century. Brakes, on the other hand, seem to have been more of a marketing item to the public than the actual applied science that the system is.
The theory of braking systems, most definitely a hard science, is not that complicated once some scientific terms are defined in common language.
Pascal’s Law and Hydraulic Operation
Pascal’s law, or Pascal’s principle, was first stated by French scientist Blaise Pascal about fluid mechanics and is a fundamental law in physics. In the simplest terms, Pascal’s principle describes that any pressure applied to a fluid inside a closed system will transmit that pressure equally in all directions throughout the fluid. This is the very reason that hydraulic power works in everything from heavy equipment and lifts to automotive braking systems.
Brake systems operate by the pressure on one pedal applying pressure to all wheel cylinders. This is Pascal’s law, which states that pressure applied to a fluid inside a closed system will transmit that pressure equally in all directions throughout the fluid.
The radial openings in most aftermarket rotors are channels or vents that go from the center of the rotor to the outside edge. These vents are often curved to draw hot air from the center of the rotor and route it to the outside, keeping the entire assembly cooler. Heat is the byproduct of the energy conversion created by braking.
The brake master cylinder is filled with brake fluid. The master cylinder is equipped with a piston that actuates when the brake pedal is pressed. This forces fluid through the brake lines to the wheel cylinders or calipers equally. The small force applied at the brake pedal produces a larger force when all four wheels are involved.
Energy Conversion
To get a vehicle in motion, an internal combustion engine converts chemical energy (combustion) into motion energy. In physics, this energy of motion is called kinetic energy. A car in motion has a lot of kinetic energy and it takes a lot of chemical energy to get up to its velocity. Having gained that kinetic energy during acceleration, it will maintain that energy unless the speed changes.
It is important to remember that the amount of work done to create this kinetic energy is the same amount of work needed to decelerate from speed to a state of rest. Physics also