Читать книгу Muscle Car Brake Upgrades - Bobby Kimbrough - Страница 8

CHAPTER 1

THE EVOLUTION OF MUSCLE CARS AND BRAKES

Vehicles are a collection of several systems; some are more glamorous or more complicated than others. An incredible amount of attention is paid to the engine, which includes the lubrication and cooling subsystems. The ignition system and the electrical system offer very complicated components and schemes. The all-important drivetrain can include iconic names, such as rock-crusher, floater, or posi-traction. Even the more basic systems, such as suspension, steering, and exhaust, have garnered more consideration by enthusiasts than brakes. Yet, braking systems have seen equally impressive technological gains in the past 50 years. Individual system scrutiny aside, no other genre of automobile has benefitted from improved braking more than American muscle cars.

While factory brakes have improved over the years, there is no one-size-fits-all solution. There is an entire aftermarket auto industry built up around automotive brakes. Each manufacturer has several different lines, all tailored to a specific purpose and application.

Muscle cars started to show more power in the early 1960s, but this 1963 Chevy Biscayne represented the last year that Chevrolet officially supported racing. In 1964, General Motors ceased involvement in racing along with Chrysler and Ford. That did not stop some of the designers from building cars for the street with some muscle that was not overly promoted in advertising. Acceleration was improving, but stopping was developing proportionately in some of the high-performance models.

American Motors Muscle Cars Front Disc Brake Offerings

AMC AMX 1968–1970: The “Go Package” option included front disc brakes starting in 1968.

AMC Javelin 1967–1974: The “Go Package” option included front disc brakes starting in 1968.

AMC Matador 1970–1975: The “Go Package” option included front disc brakes starting in 1970.

Rambler Rebel 1957–1960/1966–1967: Drum brakes were standard in all years. ■

A 1974 AMC Javelin is shown here. The AMC Javelin was manufactured and marketed by AMC across two different generations in the peak of the muscle car era: 1968–1970 and 1971–1974. The Javelin was popular in drag racing and SCCA Trans Am series. (Photo Courtesy Power AutoMedia)

A Brief History of Muscle Cars

Merriam-Webster defines a muscle car as “any of a group of American-made two-door sports cars with powerful engines designed for high-performance driving.” For our purposes, a muscle car is an American-made, two-door midsize or full-size car with a V-8 engine that is built for four or more passengers, was originally designed for street use, and was sold at an affordable price for younger buyers.

Almost every serious automotive historian considers the 1949 Oldsmobile Rocket 88 the first true muscle car. Using its new overhead valve V-8 in a lighter body that was designed for a 6-cylinder, Oldsmobile broke new ground in automotive design.

The fledgling NASCAR series was becoming the testing ground for midsize and full-size late-model cars. In the second year of the Grand National Series, the 1949/1950 Olds Rocket 88 won 10 times out of the 19 races held. A 1949 Lincoln won the first two races, a 1950 Mercury won twice, a new Ford won once, and Plymouth won four races. It didn’t take long for the car companies to realize that car sales for a model went up after winning an event. “Win on Sunday and sell on Monday” became the mantra. The new Oldsmobile even won the inaugural Carrera Panamericana.

Other manufacturers scrambled to duplicate Oldsmobile’s success, using the same game plan: a powerful engine in a light body. Most carmakers brought out limited- and special-edition cars to demonstrate their capabilities on the track. Oldsmobile maintained its dominance in 1951 before giving way to the Hudson Hornet in 1952. It wasn’t until 1955, when Chrysler brought out its C-300, that a true purpose-built muscle car hit the market. Chrysler was not shy about advertising its Hemi-powered family car as “America’s Most Powerful Car.”

Rambler, in an effort to battle with the Big Three, debuted its popular Rebel sedan. The Rebel was lightning quick for its time; when it was equipped with the optional Bendix electronic fuel injection (EFI), the Rebel sedan was recorded faster from a standing start than the 1957 Chevrolet Corvette with its mechanical fuel injection. Up to the early 1960s, the powerful muscle cars from Detroit had not developed enough power that the conventional drum braking systems were overwhelmed yet. That was soon to change.

Vintage drum brake systems and reproduction drum brake systems are still very popular with hot rodders and street rodders. These groups seldom drive their vehicles and certainly don’t risk their safety with modern highway speeds in crowded traffic.

General Motors Muscle Cars Front Disc Brake Offerings

Here is a 1970 Pontiac GTO 455. The Pontiac GTO was the third best-selling intermediate muscle car for the year and the era. There were only six GTOs ordered with the 1970-only D-Port 455 HO 360-hp package.

Buick Skylark 1961–1972: Power brakes were offered in 1953.

Chevrolet Camaro 1967–1975: Front disc brakes were optional starting in 1967. Front disc brakes were standard on SS models from 1968.

Chevrolet Chevelle 1964–1975: Front disc brakes were optional starting in 1967. Front disc brakes were standard in 1973.

Chevrolet Chevy II / Nova 1961–1975: Power brakes were offered in 1968. Front disc brakes were optional on the 1968 Nova SS and standard in 1969. All Novas had standard front disc brakes in 1975.

Chevrolet El Camino 1964–1975: Front disc brakes were optional starting in 1967 and standard in 1973.

Chevrolet Impala 1957–1975: Power brakes were offered in 1961. Optional front disc brakes started in 1969.

Chevrolet Malibu 1964–1975: Optional front disc brakes started in 1967.

Chevrolet Monte Carlo 1970–1975: Front disc brakes were standard from 1970.

Oldsmobile 88 1949–1975: Power brakes were offered in 1953. Front disc brakes were optional in 1967 and standard in 1971.

Oldsmobile 442 1964–1975: Optional front disc brakes started in 1967.

Oldsmobile Cutlass 1961–1975: Optional front disc brakes started in 1967 and were standard in 1973.

Oldsmobile Cutlass Supreme 1965–1975: Optional front disc brakes started in 1967 and were standard in 1973.

Pontiac Bonneville 1958–1972: Front disc brakes became standard in 1971.

Pontiac Grand Prix 1962–1972: Power brakes were offered in 1963. Optional front disc brakes started in 1967 and were standard in 1971.

Pontiac GTO 1964–1974: Optional front disc brakes started in 1967.

Pontiac LeMans 1964–1974: Optional front disc brakes started in 1967.

Pontiac Tempest 1961–1970: Optional front disc brakes started in 1967. ■

The Golden Era of Muscle Cars

As performance in automobiles grew, so did the popularity. While General Motors attempted to remain true to the racing ban, Dodge, Plymouth, Chrysler, and Ford began to battle it out on tracks across the land. However, things were about to change, as Chevrolet introduced the Super Sport (SS) option on the 1961 Impala. Along with the monstrous 409-ci engine, the package included tires, suspension, upgraded power brakes, and metallic brake linings.

The turning point came in 1964 when the GM floodgates opened. Buick, Chevrolet, Oldsmobile, and Pontiac entered their own purpose-built muscle cars, sliding them past GM’s brass by labeling the upgrades as heavy-duty and not high-performance. The self-imposed ban was on racing, not street performance, so the new (and younger) designers and managers in the GM automotive divisions took advantage of street enthusiasts’ passion and built cars for them. GM’s standing rule of limiting economy and midsize cars to 330 ci was dramatically pushed beyond the line by John DeLorean, then president of the Pontiac division, with the Pontiac GTO.

John DeLorean’s Pontiac GTO was a game changer in the muscle car era. The original options on the GTO included metallic brake drum linings. Even DeLorean realized that more horsepower required better braking options.

The Pontiac GTO began as an option package for the Pontiac Tempest and was a project led directly by DeLorean. It was powered by Pontiac’s 389-ci V-8 engine that was so successful in racing that it was dubbed the “Trophy V8.” The package also included a floor-shifted 3-speed manual transmission with a Hurst shifter and linkage and optional tri-power carburetion. Among the many upgrades listed were metallic brake drum linings, showing that engineers were starting to take speed and traffic safety into consideration. Original production was limited to just 5,000 units.

The car was much more popular than even DeLorean expected, and General Motors was inspired to produce more cars for power-hungry street performance car devotees. Along with GM’s confidence, other carmakers were prompted to imitate Pontiac’s best seller. It was this keeping up with the Joneses mentality that slowed down the evolution of brakes in muscle cars during the 1960s. The public wanted more powerful cars at budget prices, and Detroit automakers gave it to them.

Early Chevelle two-door coupes have been one of the most popular muscle cars to restore and modify, such as this 1965 Chevelle. Once enthusiasts add more muscle to these midsize muscle cars, disc brake upgrades should be seriously considered.

Ford Motor Company Muscle Cars Front Disc Brake Offerings

Ford Custom (500) 1964–1974: Front and rear drum brakes were offered, except the Custom 500 that had front disc brakes from 1972.

Ford Fairlane 1955–1970: Power disc brakes were an option starting in 1969.

Ford Fairlane Thunderbolt 1964: Front and rear drum brakes only were offered.

Ford Falcon 1960–1970: Power brakes were offered starting in 1964. Front and rear drum brakes only were offered.

Ford Galaxie 1958–1974: Power front disc brakes were optional in 1967 and standard starting in 1974.

Ford Mustang 1965–1973: The 1965 GT version was offered with front disc brakes. Optional power front disc brakes were offered for all models in 1967 and standard on the GT.

Ford Ranchero 1966–1975: Power front disc brakes were optional in 1968.

Ford Starliner 1960–1961: Front and rear drum brakes only were offered.

Ford Thunderbird 1955–1975: Power front disc brakes were optional in 1965.

Ford Torino 1968–1975: Front disc brakes and power assist were options in 1967. Power front disc brakes became standard on the Torino Squire Wagon in 1970 and all Torino models in 1972.

Mercury Comet 1960–1975: The GT package came with front disc brakes in 1966.

Mercury Cougar 1967–1975: Power front disc brakes were optional in some special models as early as 1969 but became standard in 1973.

Mercury Cyclone 1964–1971: The GT package came with front disc brakes in 1966. ■

A 1963 Falcon Sprint is shown here. Ford general manager Robert S. McNamara commissioned a team to create a car that was small by American standards but would be considered midsize elsewhere in the world. The Falcon became a favorite budget car for hot rodders to soup up.

The Dodge Dart, Ford Fairlane, and Chevrolet Chevelle are great examples of muscle cars from the golden era of American muscle cars. Because they are a great representation of the genre, these cars were selected to represent each of the Big Three manufacturers with the upgrades shown in this book.

Drum Brakes

A crude form of mechanical drum brakes actually appeared on a Daimler creation in 1899. It was a simple design that was nothing more than a cable wrapped around a drum. The cable was anchored to the vehicle’s chassis and controlled by the driver. Wilhelm Maybach improved upon the design on a Mercedes-Benz by using multiple steel cables wrapped around two drums on the rear wheels and controlled by a hand brake lever.

Despite these early efforts that encompassed the basic idea of drum brakes, Louis Renault is usually credited with the invention of drum brakes in 1902. Renault’s form of drum brakes would become the standard for automobiles for the next 70 years.

In drum brakes, brake shoes generate friction by rubbing against the inner surface of a brake drum that is 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).

Modern automotive brakes can be broken down into two basic types: disc or drum. While it can be argued that removing your foot from the accelerator pedal can be a form of braking (deceleration), this book only includes systems that have hard components that are designed specifically for stopping.

Air brakes, which were originally developed for railway use, have been adopted for use on larger vehicles. Air brakes are usually a complicated system of reservoirs, valves, and a multi-circuit control system that make this type of braking too sophisticated for passenger car use. Current air brake systems must be operated differently than the more common hydraulic systems, and most countries require additional training and licensing to legally drive any vehicle using an air brake system. Neither magnetic brake or electrical brake systems are currently used in passenger cars.

Muscle cars from the golden era, such as this 1966 Chevelle, are prime candidates for brake and wheel upgrades to match modern performance. There are several aftermarket brake companies that support these muscle car brake upgrades. Baer Brakes, Classic Performance Products (CPP), Disc Brakes Australia (DBA) USA, Power Brake, Master Power Brakes, Stainless Steel Brakes Corporation (SSBC), TBM Brakes (formerly known as The Brake Man), and Wilwood are all representatives in the performance brake market.

Modern rotor designs include a scalloped version for serious racing applications. Scalloped rotors are specifically designed to reduce surface area, which effectively reduces weight. Saving weight in race applications is critical for obvious reasons. (Photo Courtesy Wilwood Engineering Inc.)

Disc Brakes Australia (DBA) USA is one of many modern companies that make brake pads with a variety of different materials. Brake pads are generally broken down into three groups: organic, ceramic, and semimetallic. However, each of these groups are made up of many different types of materials. For example, organic brake pads can be manufactured from various organic compounds, such as carbon, glass, rubber, or Kevlar. Semimetallic will be made with iron, steel, copper, or graphite in the friction material. Ceramics tend to be made of a manufacturer-specific ceramic compound. Each type has its own pros and cons.

Brake linings and the materials used have seen dramatic changes since their first application in 1888. Various soft metals have been used with noisy results. Asbestos linings worked well but posed a health hazard, so their use was stopped. Synthetic fibers have taken over the lead role in brake lining material. Use caution when dealing with older brake shoes like these. Avoid breathing the dust and try not to disturb the dust and fibers with compressed air or vacuum cleaners.

Disc Brakes and Brake Pad Linings

British inventor William Lanchester patented the disc brake in 1902, which was little more than soft copper brake pad linings that moved against a metal disc, transferring heat better but screeching brutally when applied.

Another British inventor, Herbert Frood, developed brake pads using asbestos as the lining. This quieted the braking action and gave Frood acknowledgment as the inventor of the brake pad by having developed a more efficient frictional surface. Asbestos was used in brake linings into the 1980s, when health concerns forced the mineral’s removal from the automotive industry.

In the United States, one of the first to manufacture drum brakes was the A. H. Raymond Co. of Bridgeport, Connecticut, which opened in 1902 as a four-man shop that built brakes, brake linings, and clutch facings. Renamed Royal Equipment Co. by 1904, the company continued to improve brakes, particularly with a natural silica material called asbestos and copper-wire brake lining known as Raybestos.

These Raybestos brake linings were sold as double acting brakes. Advertising reported the double action as the ability to stop forward or backward motion. This claim left motorists believing that stopping in both directions was impossible before.

Duesenberg began putting brakes on the front wheels as well as the rear wheels in races during the 1915 events. This allowed the cars to carry speed longer before braking to enter corners. This setup required the driver to use a separate foot brake and hand brake to control the braking. A unit that combined both brakes into one pedal to operate the four brakes didn’t come along until 1919.

Chrysler Corporation Muscle Cars Front Disc Brake Offerings

Shown here is a 1970 Dodge Charger R/T. The standard engine on the R/T was the 375-hp 440-ci 4-barrel. For a few hundred dollars more, consumers could have the 425-hp 426-ci Hemi. For 1970, there was also the 390-hp 440-ci with a trio of Holley 2-barrels.

Dodge 330 1962–1964: Front and rear drum brakes were offered.

Dodge 440 1963–1964: Front and rear drum brakes were offered.

Dodge Challenger 1969–1974: Front disc brakes were standard.

Dodge Charger 1966–1975: Front disc brakes were an option from 1967.

Dodge Coronet 1965–1975: Front disc brakes were an option from 1967.

Dodge Dart 1959–1975: Front disc brakes were optional in 1965 and standard on the Swinger in 1970. They did not become standard on all models until 1976.

Dodge Lancer 1961–1962: Front and rear drum brakes were offered.

Dodge Polara 1962–1964: Front and rear drum brakes were offered.

Dodge Super Bee 1968–1971: Front and rear drum brakes were offered.

Plymouth Barracuda 1964–1974: Disc brakes were optional starting in 1965.

Plymouth Belvedere 1955–1970: Front and rear drums were offered. Front disc brakes were optional from 1967 on.

Plymouth Duster 1970–1975: Front disc brakes were standard on 318 and 340 models starting in 1973.

Plymouth Fury 1961–1964/1974–1975: Front and rear drum brakes were offered from 1961–1964. Front disc brakes were standard from 1974 on.

Plymouth GTX 1966–1971: Front and rear drum brakes were offered. Front disc brakes were optional from 1967 on.

Plymouth Road Runner 1968–1975: Front disc brakes were optional from 1968.

Plymouth Satellite 1964–1974: Front and rear drums were offered. Front disc brakes were optional from 1967 on.

Plymouth Savoy 1962–1964: Front and rear drum brakes were offered.

Plymouth Superbird 1970: Front disc brakes were offered.

Plymouth Valiant 1960–1975: Power front disc brakes were available in the Scamp package in 1974 and later. ■

Ford did not offer hydraulic brakes until the 1940s, so many of the 1932 Roadsters seen today with hydraulic drum brakes are perfect examples of the earliest OEM-style brake swaps.

Hydraulic Brakes

About the same time, Malcolm Loughead (Lockheed Corporation) designed the first hydraulic braking system. Mechanical brakes, which were a simple design, required more effort from the driver, and unless the system was maintained frequently, the brakes did not apply pressure to all wheels evenly, causing control issues.

The Model A Duesenberg was the first production car to use four-wheel hydraulic brakes in 1921. Very few cars used the four-wheel hydraulic brakes in manufacturing until 1923. Chalmers began offering this as an option for the fairly steep price of $75, which is about $1,053 today.

Walter P. Chrysler, a product of the Chalmers company before starting his own car company, used the four-wheel hydraulic brakes based on the Chalmers system, but Chrysler’s were fully redesigned. Incorporating rubber cup seals in place of the leaky rawhide seals that Lockheed used, the Chrysler hydraulic brakes were more dependable. Loughead allowed Chrysler to use his design as long as he was able to use Chrysler’s improvements.

The new system was referred to as the Chrysler-Lockheed hydraulic brakes and was used in Chryslers from 1924 to 1962. Undeterred by the cost to make such a system, Buick and Cadillac also began to make four-wheel brakes standard equipment on their cars. Car builders that did not want to offer the four-wheel brakes made outrageous claims that they were unsafe. By the end of the decade, it was clear that four-wheel brakes were not only here to stay, they were the standard.

As hydraulic brakes continued to improve, more and more manufacturers opted to use the hydraulic brake system over the durable mechanical brakes. Chevrolet and Ford were holdouts until Bendix, the company that supplied General Motors with mechanical brakes, bought out Lockheed and began manufacturing hydraulic brakes. General Motors then switched to hydraulic four-wheel brakes for all of its cars in the mid-1930s. Ford continued with mechanical brakes until the early 1940s, when it finally adopted the hydraulic brakes. Ford was the last automaker to do so.

Strangely enough, mechanical brakes are still common on many muscle cars. Parking brake systems, such as this Wilwood brake system, still use brake shoes and cable actuation for the parking brake. Brake shoes work well in this fashion because they are only used to hold the car in one spot and not to slow the car down at speed.

Chrysler’s Crown Imperial was always a top-of-the-line luxury car, but it could have been argued that it was an early entry into the muscle car market. Advances in power and braking made the Crown Imperial a favorite to many, but high cost and extravagant styling moved the marquee out of the muscle car arena before the movement even began. This 1957 example shows the tipping point when luxury won out over performance in the nameplate.

Post-War Developments

Disc brake technology improved in large part due to the automotive industry borrowing designs from World War II aircraft. Chrysler’s 1949 Crown Imperial and the 1950 Crosley Hotshot are the most notable of these examples.

Initially, the hydraulic brake master cylinders were a single-reservoir-type system. In the early 1960s, the hydraulic brakes and hydraulic clutch systems were operated from the same master cylinder, such as the one pictured. In the mid-1960s, the dual master cylinder appeared with two wheels operating from the front part of the master cylinder and the other two wheels operating from the rear portion of the master cylinder. The most common early dual systems were a split front/rear system. In 1967, American Motors Corporation (AMC) produced cars with a diagonal split system, where the right front and left rear are served by one actuating piston and the left front and the right rear are served by a second actuating piston. This system became the preferred split system in the 1970s.

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 tells us that the total energy of an object remains constant; energy cannot be created or destroyed but only transformed from one form to another. This is also known as the law of conservation of energy. The braking system uses friction to convert the kinetic energy into thermal energy.

There are many factors that combine to make this energy conversion happen, including the brake pedal ratio and brake line diameter. Without getting into too many details, here is a basic overview of how most brake systems work:

The vehicle operator steps on the brake pedal to slow down or stop. The brake pedal lever is connected to a rod that pushes a piston in the brake master cylinder. The master cylinder is filled with hydraulic fluid that gets pushed into the brake lines by the piston. The hydraulic fluid presses against pistons in slave cylinders located on each wheel. The slave cylinders actuate either brake shoes or caliper pads against the brake drum or brake rotor, applying enough force to stop the vehicle.

Here’s where physics comes in. As the brake shoes or pads do their job, the kinetic energy of the vehicle is changed into heat. The biggest enemy to brake pads and brake shoes is heat. As the brake shoes or pads change the car’s motion energy into heat, the brakes get hotter. If they get too hot, they won’t work as well and will experience brake fade. It they get hot enough, the brakes will lose their ability to stop the car because the shoes or pads lose their friction against the drum or rotor. The amount of heat generated by the brakes stopping a car at speed can hit 950°F or more.

To combat brake fade, manufacturers use different materials with higher heat resistance for different applications. These materials that resist degradation at high temperatures include composites, alloys, and even modern ceramics. Some of these materials, especially those used in the higher-performance brake sets, have brake rotors and pads that require some heat in them to have enough friction in the first place. When they are cool, the brakes don’t have enough friction and won’t stop the car as well. These types of brakes are used mostly in race cars and not on cars driven on the street. Using brakes kits with different materials in the rotors, pads, shoes, or drums is one way to improve braking in muscle cars.

The brake pads ride very close to the rotor when they are not in actual contact. This leaves precious little room for cooling. Brake pad materials rely on mostly heat-resistant synthetic fibers to resist heating and brake fade. Ceramics and metal fibers from copper and other soft metals are also used in modern brake pads.

Most cars manufactured during the muscle car era were equipped with drum brakes on all four wheels. Modern braking systems tend to have disc brakes on the front and drum brakes on the rear. More-expensive models have four-wheel disc brakes. Disc brakes do a great job stopping a car and are simplistic in design and maintenance.

Another method to increase the braking in vintage muscle cars is to add disc brakes to the front wheels with parts intended for a similar-model car or from a kit designed by a manufacturer to work with the model of car you are performing the upgrade on. Since the front brakes do 75 to 90 percent of the braking, changing from drum brakes to disc brakes on the front is one of the most effective braking upgrades.

Stability, Steering, and Stopping Distance

Tires are literally where the rubber meets the road. Tires are the link between the vehicle and the road surface, and they are the final piece of the braking system. Tires actually stop the vehicle and play an important role in the change of speed and direction. Because these circular devices are involved in transmitting braking, motion, and lateral forces, any one of these forces can and will affect the others. The Motorcycle Safety Foundation (MSF) teaches its riders about this concept in what it calls “the traction pie.”

The MSF has a traction pie graph that represents the total amount of traction that a tire can have. The pie-like segments define areas for acceleration force, braking force, turning, and a reserve. The four segments of the traction pie are ever changing, shrinking, or growing, depending on the action happening at the time. For example, under strong acceleration, that segment of the pie will be larger. The braking segment will shrink to nearly nothing, and turning will probably be somewhere in size between the acceleration and the braking segments. The reverse would be true if the condition was hard braking instead of hard acceleration.

The MSF goes on to explain that the total traction can be consumed by those three segments when they consume all the reserve. After that point, the tires will lose traction. In this explanation of traction, brakes play a key role in stability, steering, and stopping.

In addition to the various brake components, aftermarket manufacturers often produce their own lines of spindles and steering arms too. Spindles can be purchased that raise or lower the ride height of a vehicle but keep the steering geometry correct.

In a traction pie concept from the Motorcycle Safety Foundation (MSF), a circle that represents the total amount of traction available is divided by forces that consume that traction. Acceleration and braking take a large part of the available traction. Turning consumes some of the traction, and whatever is left over is held in reserve. According to the MSF, a reserve should always be maintained. If the reserve is fully consumed, a loss of traction will result in a skid or a spin.

Engineering Details of Braking Performance

The engineering behind brake performance is much deeper than most motorists realize. A great number of factors need to be considered when designing a brake system for a specific vehicle. The vehicle itself figures into these equations.

“The effectiveness of any brake system depends on factors like the weight of the car, braking force, and total braking surface area,” said Mark Chichester of Master Power Brakes. “You have to factor in how efficiently the system converts wheel motion into heat and how efficiently the built-up heat is removed from the brake system. The buildup and dissipation of heat go a long way toward explaining the major differences between drum and disc brakes.”

Drum brakes are at a clear disadvantage when it comes to dissipating heat. As drum brakes get used hard, the brakes fade because of excessive heat buildup in the drum. The drum absorbs heat until it reaches a saturation point and is unable to absorb additional heat.

With disc brake systems, the rotors are not confined in a tight space; they are exposed to the outside air that provides a cooling effect and helps combat brake fade. Most basic disc brake conversion kits have rotors that are made of cast iron.

Cast iron is inexpensive and has great wear properties. Cast iron is also heavy, so those enthusiasts looking to gain performance by losing weight may want to consider rotors made from other materials, such as ceramic composites. Kits with these ceramic composite brakes are engineered to be heat resistant and able to handle higher compressive loads at higher temperatures.

Force Conversions

To understand how the force from stepping on the brake pedal is converted into pressure at the brake’s friction pad or shoe, some elements of the common components in the braking system must be explained.

The force of a driver stepping on a brake pedal to stop a car traveling at a high rate of speed would need to be tremendous if the force wasn’t multiplied. For instance, a young soccer mom in a 4,000-pound sport utility vehicle (SUV) running down the highway at 70 mph would need to use all 120 pounds of her body weight along with both feet standing on the brake pedal to even start slowing down the vehicle. Using that illustration, it is obvious that multiplying the force applied to the brake pedal is critical when engineering a braking system.

Heat is the enemy of brakes, and one of the key advantages to using disc brakes is that they are more effective in the heat due to their ability to shed heat better.

The vacuum-operated brake booster works today much as it did 50 years ago when muscle cars ruled the road. Drawing vacuum on the front of the diaphragm removes atmospheric pressure. The rear chamber is vented to the atmosphere and the pressure multiplies the force a driver applies with the brake pedal. This cutaway shows where the diaphragm placement in the brake booster is and how it works in relationship to the brake pedal actuator rod.

How the force is amplified from the driver’s input into braking force is referred to as brake system gain. This gain is done mechanically and through vacuum assistance. It all starts with the driver stepping on the brake pedal. Without extra exertion, an average-size person delivers about 70 pounds of force on the brake pedal pad. The brake pedal is really a mechanical lever, and the positioning of the pedal pad in relationship to the mounting point (where the pedal pivots) and the point where the pushrod is attached to the master cylinder is how the force of the driver’s action is multiplied.

How Upgrades Affect Vehicle Performance

There are several things to consider when planning a brake upgrade. These include gain, modulation, heat capacity, cooling rate, and weight.

Gain

Gain is a fancy term for multiplying the mechanical advantage. These gains can come from changing the pedal ratio, adding a brake booster, upgrading to a larger caliper piston size, or changing the size of the rotor. Larger discs allow for more brake torque because the brake pad will apply pressure at a larger radius, while larger caliper pistons (or more pistons) result in more area of applying a specific pressure.

One of the quickest and easiest ways to improve gain in the braking system is to change the brake pedal. The braking ratio can be changed with an increase or decrease of distance between the pedal’s hinge point and where the master cylinder piston connects to the pedal.

Modulation

Brake modulation, in the simplest terms, is the ability to slow down or stop without locking up the brakes. Peak stopping power is just before the brakes lock up. The ability to control that peak range precisely is the goal of a well-designed brake system. Brake system upgrades usually have a better pedal feel and firmness with an improved ability to control brake lockup.

Heat Capacity (Thermal Mass)

Heat is the enemy of brakes. When temperatures get high enough, the brake pads start fading and eventually lose the capacity to work properly. Heat is frequently absorbed by the brake system components, which can be dissipated at a rate depending on the mass and material. Thermal mass or thermal capacity are terms often used to describe the ability of the brakes to shed heat without reaching temperatures that would interfere with proper braking. Modern aftermarket brake systems use materials and component designs that allow for higher heat capacity.

Cooling Rate

Upgraded brake systems usually have better cooling through material and venting design. Slotted and drilled rotors, curved cooling vanes in rotors, materials with better heat dissipation, and a larger surface area all factor into manufacturing modern aftermarket brake systems. In addition, drum brakes are enclosed. All of the heat is trapped inside the drum. Disc brakes have rotors that are exposed to airflow and more efficient cooling.

Weight (Unsprung and Rotating)

Converting from drum brakes to disc brakes often results in a substantial weight reduction. Whenever there is a weight loss, two terms apply: sprung/unsprung weight and rotational weight.

Sprung weight is any portion of the car that is held up by the coil springs; the rest is unsprung weight. The largest part of a braking system (drums or discs and calipers) is unsprung weight. For performance, car builders try to minimize the unsprung weight because it hurts handling. This weight is supported by tires and shocks.

Rotational weight is any part that rotates when speed is accelerated or decelerated. It takes more horsepower to turn rotating weight and to decelerated rotating weight. Taking off the heavy drum brakes and installing lighter rotors helps minimize the amount of rotating mass. This is also an important factor when upgrading to aftermarket wheels. Increasing weight requires more horsepower to turn and more brake force to slow down.

Modern Braking Performance Versus High Performance

When it comes to selecting a disc brake conversion or improving to a higher-performance braking system, a few factors come into play. What are your plans? Will the car be used as a daily driver to enjoy driving back and forth to work and home, or will it be going to the track, doing some canyon carving, or hitting the autocross course regularly? As with almost anything else, the budget for it will likely play a large role in the decision.

If you are simply looking for an up-to-date brake system that is compatible with today’s city traffic, or the budget is tight but you still want safe and confident braking, then an OEM-style replacement brake conversion kit is probably all you need. However, if you are hitting the track, a mid-level or high-performance kit will probably serve your needs better.

Evaluating an aftermarket brake system boils down to a few critical elements.

Larger Disc Radius: A larger disc radius allows for more brake torque. The brake pads will apply more pressure over a larger radius by virtue of being farther from the center of the wheel. Selecting the largest rotor that fits safely within the wheel is helpful for good braking force.

Caliper Piston Area: Selecting a kit with larger pistons or more pistons (increasing the piston area) allows the system to increase the brake force due to larger piston area. If the line pressure remains consistent, the increase in piston area means the applied force will increase.

When converting from factory-original drum brakes to aftermarket disc brakes, the differences are very noticeable. The weight difference is visually obvious.

In addition, the drum brake shoes are contained in the drum and shielded away from cooling airflow. Any debris from the shoes are also contained in the drum. Disc brake rotors and pads are open to the environment and make better use of cooling and cleaning.

Increasing Line Pressure: Increasing line pressure by adding a power booster or improved pedal ratio helps increase braking force.

Material Selection: Selecting brake pad and rotor material to improve the coefficient of friction between the pad and rotor can increase the braking force. There is a tradeoff when generating more friction, which is more heat. Larger rotors will help shed heat, especially if the rotors are designed with cooling in mind.

Rotor Design: In addition to larger rotors, cooling vents that allow for airflow through the center of the rotor greatly improve the ability to efficiently provide cooling and prevent brake fade. Slotted and drilled rotors assist by allowing gasses to escape and remove particles that are created by brake pads and rotors during braking.

The caliper piston area varies from manufacturer to manufacturer and even different-sized calipers can be found within the same manufacturer’s line of products. This is a compact single-piston caliper from Wilwood Engineering. (Photo Courtesy Wilwood Engineering Inc.)

The research engineering and product development is very specific to different applications. Multi-piston calipers may even have different-sized pistons in the same caliper housing.

Piston area alone is not the only determining factor for which brake system is best for your application. Pad material, rotor radius, and construction all play a role.

A brake booster is designed to provide power assistance to the braking effort, meaning you do not have to put a lot of force on the brakes for them to actually operate and engage the rotors. The brake booster is located between the brake pedal and master cylinder and uses a vacuum to overcome the fluid pressure in the braking system. This is covered in detail in chapter 2.

Types of rotors, calipers, hubs, and brake pads have changed over the decades. Modern technology has affected the manufacturing process as well as the materials and design of these components to make them higher performing and more durable than ever before.

Some rotors are solid one-piece units, while others are multi-piece construction for strength and cooling properties featuring slotted and vented designs.

The rotor design, construction, and material are critical factors in a modern performance brake system. The Society of Automotive Engineers (SAE) maintains a specification for the manufacture of grey iron for various applications, including passenger cars.

Rotor hubs are often manufactured with slots in the hub to help with cooling without sacrificing strength or structural integrity in the component. This technology was not used in the muscle car era but is available in aftermarket brake kits now.