How Ford’s Revenge Against Ferrari Helped Everyone Get Better Brakes

Early brake systems

This is the surprising, convoluted story of the invention and refinement of various brake technologies–how the best designs languished for decades before becoming readily available–and the role that a rivalry between Ford and Ferrari played in popularizing and improving the brakes we all have today.

In 1898, Elmer Ambrose Sperry designed an electric car. The front-wheels had disc brakes built by the Cleveland Machine Screw Company. Sperry’s brakes were operated by an electromagnetic system. Four years later the builder of an English car, the Lanchester, patented disc brakes. The brakes on the Lanchester proved unpopular because of some design flaws. The brake rotors (discs) were very thin, likely undersized for the car. The friction pads were lined with a soft copper that screeched loudly and wore rapidly. Brake manufacturer Ferodo produced a disc brake system for the AC Cyclecar in 1914. Production stopped during World War I and never resumed.

Louis Renault patented drum brakes in France, the same year that disc brakes were patented in England. The early drum brakes were not very satisfactory in many respects, but they had one important advantage over disc brakes. Most drum brakes have a self-energizing, servo effect. This allows drum brakes to use the rotational force of the drums to increase the pressure on the brake shoes. This servo effect allowed drivers (even petite drivers) to control heavy cars without excessive pressure on the brake pedal. Drum brakes soon dominated the auto industry, and disc brakes were not tried on cars again for many years.

In 1907 Herbert Frood developed the idea of using asbestos as a brake lining material. Asbestos proved to be much more durable than other materials that had been tried. It quickly spread throughout the industry.

The brakes on each wheel were operated by mechanical linkages. Meticulous adjustments were required to get balanced braking from all four wheels. The mechanical links wore and required frequent readjustment. In 1917 Malcolm Loughead ( later changed his name to Lockheed) patented a hydraulic system to activate brakes. The first car to offer hydraulic brakes was the 1921 Duesenberg. Lockheed’s design started replacing mechanically operated brakes, eventually becoming a standard in the industry.

Excess heat

Three things can happen when hydraulically operated drum or disc brakes overheat:

1. The brake friction material can emit gases which separate it from the disc (rotor), or drum. This reduces the effectiveness of the brakes and is called fading. It comes on incrementally as the brake lining material heats up.
2. If the overheating continues the surface of the brake friction material can begin to melt. After cooling it has a hard glazed surface with much reduced friction.
3. In the final stage of overheating the brake fluid can boil. The brake pedal suddenly goes to the floor board, and there is no braking whatsoever until the brakes cool and the vaporized brake fluid condenses back into liquid.

Drum-type brakes trap heat inside the drums where it is not dissipated effectively. Disc brakes are better at dissipating heat, they also tolerate high temperatures better than drum brakes. However, they can overheat. Drivers in mountainous areas are taught to use their brakes sparingly when descending long steep grades.

Centrifugally ventilated disc brake

In 1929 Ralph G. Rosenberg patented a new type of rotor for disc brakes. Although the rotor was one piece, you could think of it as two discs joined by several fins radiating out from the center. A large opening in the center of the rotor allowed air to enter. This design accomplished two things:

1. It doubled the surface area available to cool the rotor.
2. It allowed centrifugal force to pump air through the rotor when it was spinning.

During the 1930s the Rosenberg disc brake was adapted and used on railway cars. The Girling, and Lockheed brake manufacturers built non-ventilated disc brakes for a couple of limited-production specialty cars during this period—they were discontinued after a few years.

In the 1930s an engineer named Jesse Hawley patented a disc brake with a solid (non-ventilated) rotor that had a different method of mounting the caliper. The caliper is the part that squeezes the rotor to slow its rotation. In 1949 Hawley licensed his brakes to the Crosley car company. Crosley began offering the brake system as an option on the Crosley HotShot. Unfortunately these brakes were constructed with the wrong type of metal which led to some serious corrosion problems. Many Crosley owners converted their disc brakes to the earlier drum brakes. The next year Crosley dropped the disc brake option.

Some sources claim that the Crosley HotShots had a ventilated disc that was originally designed for aircraft by the Goodyear tire company. However a member of the Crosley club who has seen several HotShots reported that the discs were solid, not ventilated.

Europe begins using disc brakes

The 1951 British Racing Motors (BRM) Type 15 was the first Formula 1 car to use disc brakes (not ventilated). Jaguar began experimenting with disc brakes (solid rotors) on their C-Type cars in 1952. In 1953 the Jaguars won decisively at the 24 hour race in Le Mans, France. Other European manufacturers noticed, and began to consider disc brakes.

The 1955 Austin-Healey 100S was a limited production race car that had Dunlop solid discs on all four wheels.

In 1955 Citroën built 69 pre-production examples of their new DS model which had solid rotors on the front wheels. The follow year the car went into production.

Triumph entered three TR2s at Le Mans in 1955 to experiment with three brake configurations:

1. 1. Drum brakes on all four wheels
   2. Girling solid rotors on the front, and drums on the rear
   3. Dunlop solid rotors on all four wheels

In 1956 Triumph began production of their new TR3 model which had Girling solid rotors on the front wheels. At the same time Jensen began production of their 541 Deluxe model with solid discs on all four wheels.

Colin Chapman redesigned the Vanwall Formula 1 car for 1957. This was the first car to use ventilated disc brakes. The Vanwall cars had some problems but the ventilated brakes performed well.

The 1959 250 TR was the first Ferrari sports car to use disc brakes (not ventilated). The first Ferrari Formula 1 car to have disc brakes (not ventilated) was the 1959 246 F1.

Ford re-enters racing

The next recorded use of ventilated rotors on cars occurred in the 1960s. In 1962, Henry Ford II withdrew his company from the 1957 Automobile Manufacturers Association ban on racing. Other American auto manufacturers were already questioning the ban which prohibited any direct involvement in racing. The ban had taken a toll on Ford’s image, and its ability to engineer performance, reliability, and safety. Racing revealed flaws in Detroit’s products and provided opportunities for experimentation and improvement.

One of Ford’s goals was to get involved in endurance racing, where European cars dominated. In 1963 Ford learned that the Italian auto maker Ferrari was for sale. Ferrari had been almost unbeatable for several years in the GT and Prototype classes in endurance racing. Ford wanted to get a foothold in that type of competition. The company spent millions on an inventory of Ferrari’s assets and liabilities. It spent millions more studying the legal minutiae of the purchase. Henry Ford II negotiated with Enzo Ferrari and thought they had an agreement. Two of Ferrari’s requirements were:

1. Ford would be in charge of the street-legal cars which would be called  Ford-Ferraris.
2. Ferrari would be in charge of the racing cars which would be called Ferrari-Fords.

Enzo Ferrari backed out of the sale when he learned that Ford didn’t want Ferrari to build a car that would compete with the Ford-powered Lotuses at the Indianapolis 500. Some people believe that Ferrari had expected to have unrestricted control of the racing program after selling to Ford. Others say that Ferrari never intended to sell to Ford and was just using the negotiations as a fact-finding exercise. Ford determined that it would build its own endurance racing car and defeat Ferrari where it would do the most damage—the 24 hour endurance race that took place each June on the public roads of Le Mans, France.

Ford rushed to create a new car for the Le Mans Prototype 1 class. Engineer Roy Lunn from Ford of Britain was given chief design responsibility. He had previous success at Le Mans when he designed the Jupiter Javelin for Jowett cars, Ltd. in 1950. He was Ford’s only engineer with previous experience designing a mid-engine car, the Mustang I concept car.

Ford still wanted a partner with current experience in building mid-engined cars, and competing in international races. The company approached Lotus because the two companies were already collaborating  on a car for the Indianapolis 500. Lotus was over-committed at the time. Founder, Colin Chapman demanded a enormous cash payment, and that the cars be called Lotus-Fords. Ford declined.

Next, Ford approached the British company Lola which had recently built a cutting edge race car with a Ford engine. They worked out an agreement in which Lola would supply Ford with two examples of the Lola Mk6 , and the services of Lola owner Eric Broadley as a consultant. The Mk6 became the starting point from which Ford would build its new endurance racer. Aston Martin racing director John Wyer was hired to be the team manager.

The one iron-clad requirement for the new car was that it had to use a V8 derived from a Ford passenger car engine. This would make the car hundreds of pounds heavier than its competitors.

The Lola’s engine was located the in the middle of the car, behind the driver. This allowed the driver to be lowered into a semi-reclining position because he didn’t have to look over the top of an engine. The result was very low car, with less aerodynamic drag. When Ford built the new racer based on the Lola Mk 6, they called it the Ford  GT40 because the roof was only 40 inches from the ground. After further development this car was called the Ford GT40 Mark (Mk) I.

Brakes were one of the biggest challenges Ford faced in developing the GT40. Le Mans demands more from braking systems than the other courses. The course has numerous turns, but the one that requires the most severe braking is the 35 mph Mulsanne Corner at the end of three-mile long Mulsanne straight. Most of the cars in the top prototype class were exceeding 200 mph on that straight. Cars that could delay braking until the last possible moment obviously had an advantage over cars that had to begin braking earlier.

The Ford team tried all of the usual techniques to improve brake performance: the largest rotors (discs) that would fit without completely redesigning the car; the most heat-resistant brake pad materials; large air ducts blowing on each brake rotor; grooves and holes in the rotors to increase the surface area and allow gases to escape. But it wasn’t enough for all the energy the brakes had to absorb. There were photos of the Ford GT40s with their brake rotors glowing red-hot.

In addition to the problem with brakes, there were many other problems typical when sorting out a new car. Three GT40s were entered at Le mans in 1964. Two retired with transmission problems, and one with a broken fuel line. Companies like Ferrari and Porche were more effective at testing and debugging new race cars—they had been doing it forever.

Brake manufacturers offer the Rosenberg ventilated rotor

AC Cobra builder and retired race-car driver Carrol Shelby replaced John Wyer as team manager toward the end of the 1964 season. Ford engineers discovered that when a driver steps on the brake pedal at 200 MPH, the temperature of the brake rotors jumps to about 1500 degrees fahrenheit.

During preparations for the 1965 Le Mans race, Kelsey-Hayes supplied the Ford GT team with new ventilated rotors that were similar to the Rosenberg-type centrifugally ventilated rotors. These helped cool the brakes but it was not enough for the extreme conditions. The drivers were still not able to do the aggressive braking they preferred as they approached the Mulsanne Corner. The improved cooling actually aggravated another problem. Rotors sometimes cracked as a result of the repeated heating/cooling cycles.

Ford did a lot of testing on brake dynamometers. They simulated repeated laps at Le Mans in order to replicate the brake problems they had seen on the track. Rotors made from various types of cast iron were tested as well as copper coatings on the rotors. Uncoated rotors made of a particular type of nodular cast iron performed the best.

New brake pads were engineered to survive 48 hours of Le Mans type competition—twice the distance of the race. The revised car with the new brake rotors, a larger engine, a better transmission, improved aerodynamics, and 17 other refinements was called the GT40 Mk II. The older cars were renamed the Ford GT Mk I.

In 1965 six Ford GTs started at Le Mans in 1965, a mixture of Mk I and Mk II models. None of them finished. Testing and refinement continued, greatly improving reliability. In 1966 the Ford team finally humiliated Ferrari, finishing 1st, 2nd, and 3rd at the 24 Hours of Daytona, the 12 Hours of Sebring, and the 24 Hours of Le Mans.

Ford was working on a completely new replacement for the Ford GT Mk II. Unlike the previous GTs, the new car was designed and built in the U.S. The chassis was made of an aluminum honeycomb material developed for aircraft. The body was redesigned to take advantage of a new Appendix J in the rule book allowing the greenhouse area of the cockpit to be narrower which reduced wind resistance.

The new cars were initially nicknamed J cars. They incorporated several other leading edge technologies. Ford worked with Kelsey-Hayes to create new 12 inch rotors that were 1.25 inches thick. Replacing the 15 inch wheels with 16 inch wheels improved air flow around the brakes. These changes finally gave the Ford GTs the braking capacity they needed for the most extreme demands. Extensive testing had also improved the aerodynamics and various other aspects of the car.

After the J cars were ready for competition in 1967 they were officially dubbed Ford GT Mk IVs. A Mk IV finished 1st and a Mk II was 2nd at Sebring. A Mk IV also won at Le Mans, finishing 32 miles ahead of the second place Ferrari.

The governing body for endurance racing was concerned about safety as the speeds at Le Mans got higher. The Mk IVs had been clocked at 220 mph on the Mulsanne straight.  The organization changed some of the rules, reducing the maximum allowable engine size, which made the Ford GT Mk IVs obsolete.

In 1968, and 1969 a private team run by John Wyer won at Le Mans with redesigned Ford GT40 cars using smaller engines. In 1970 the rules were changed again, making Ford GT40s no longer eligible for prototype racing.

Why the long delay in adopting better brakes?

The self-energizing servo effect of drum brakes provided the advantage of lower pedal pressure. That was one of the main factors that kept drum brakes dominant for six decades. The servo effect also entailed some serious disadvantages. Drum brakes are hyper-sensitive to any changes in the amount of friction between the brakes shoes and drums. When the friction coefficient was changed by water in the brake drums, or excessive heat build up, drum brakes can become almost completely useless.

The other disadvantage of the self-energizing servo action is that it is very difficult to engineer drum brakes to have a predictable, linear relationship between pedal pressure and braking action. Caliper-type disc brakes are inherently linear and predictable. If the power-assist system is also designed to be linear, then it is easy for a driver to get the braking action desired by applying the a known amount of pedal pressure.

When cars started growing larger and heavier in the 1950s, the servo effect was no longer enough to keep brake pedal pressure requirements reasonable. Power-assisted brakes were becoming popular. The fact that disc brakes also required power assist was no longer a disadvantage.

Non caliper-type disc brakes had been used on Chrysler Imperials from 1948–1954. They were less successful than caliper-type disc brakes, but that is another story.

Detroit was promoting high performance cars in the 1960s. It began to follow Europe’s lead in offering disc brakes. Here are some milestones in the evolution of disc brakes:

• The 1964 Studebaker Avanti came with solid disc brakes on the front wheels, the first American car to have caliper-type disc brakes since the Crosley HotShot.
• The 1964½ Ford Mustang offered optional ventilated discs on the front wheels.
• The 1965 Thunderbirds, and Lincoln Continentals offered optional ventilated discs on the front wheels.
• The 1965 Corvette offered ventilated disc brakes on all four wheels.
• The 1965 Ramblers came with disc brakes on their front wheels as standard equipment.

Why did it take so long for a racing-car builder to consider the Rosenberg brakes? Most of the racing in the US is done on tracks with no sharp turns. The wide turns that do exist are often banked to keep speeds as high as possible. Braking is not much of a factor in this type of competition. The racing that was done on the few tracks with sharp turns was dominated by European cars and a few American sports cars like the Corvette and AC Cobra because they were better at braking and cornering.

A sizeable budget was needed to experiment with things like ventilated brake rotors. It took a large company like Ford that was interested in races that challenged the braking systems. When Carrol Shelby was put in charge of developing the Ford GTs in 1965, he asked Henry Ford II what the budget for was the Le Mans Project. Ford replied “Just win the race.”

Centrifugally ventilated discs for everyone

By the late 1960s many cars were offering optional disc brakes on the front wheels, most of them were the Rosenberg-type centrifugally ventilated rotors. By the late 1970s all of the cars and light trucks sold in the U.S. had switched to centrifugally ventilated rotors on their front brakes. Many high performance and racing cars (including Ferraris) used them on all four wheels.

Additional references

http://www.motorsportmagazine.com/archive/article/may-2000/53/disc-brakes

https://www.hemmings.com/magazine/hsx/2011/04/The-first-car-with-disc-brakes-really-was——/3698201.html

http://www.secondchancegarage.com/public/history-of-automotive-brakes-1.cfm

http://www.roadandtrack.com/car-culture/classic-cars/features/a24716/phil-hill-on-the-gulf-oil-ford-gt40p/

http://www.ultimatecarpage.com/car/3406/Ford-Mk-IV.html

http://www.roadandtrack.com/car-culture/classic-cars/features/a24716/phil-hill-on-the-gulf-oil-ford-gt40p/

http://www.topspeed.com/cars/ford/1964-1969-ford-gt40-ar133984.html