Muscle Car Brake Upgrades. Bobby Kimbrough
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.
CHAPTER 2
COMPONENTS AND THEIR FUNCTIONS
With the fundamentals of the hydraulic brake system understood, it’s time to review the many components within the automotive braking system. Similar to the vehicle they’re used to slow and stop, there are many variables, accessories, and styles of components used depending on the application.
As the majority of automotive brake systems operate on the same principles of hydraulic pressure and physics, many of these components are common to nearly any car on the street or track. Granted, advanced electronics have stepped into the braking performance world with antilock systems on newer vehicles, but we’ll keep our focus on the braking systems used in the majority of hot rods, muscle cars, and road-course warriors being built and run on the track. Many of these components were lightly covered in chapter 1, but the following sections break them down in greater detail through a systematic approach.
Brake Pedal and Assembly
Since the braking process begins with your foot pressing the brake pedal, it is fitting to start our discussion there. The brake pedal assembly is one component that is probably taken for granted when a brake system upgrade is planned, but it should certainly be considered and reviewed to see how it could be improved.
Like engine parts, brake system components come in a lot of shapes and sizes, depending on your application and braking performance expectations.
The brake system starts with your foot pressing a pedal, so weigh your options for pedal position and movement along with how much pressure you’re comfortable with providing.
The pedal assembly acts as a simple lever. There is another rod connected to the lever that forces a pushrod into the master cylinder chamber to pressurize the brake system. The position and length of the pedal lever and its pivot point affect how much force is supplied to the master cylinder and how much force is required. It is also important to consider the location of the brake pedal in relation to the throttle and clutch pedals. Many older cars or trucks have quite a space between the pedals, which will not bode well in a performance application.
Depending on the goals for your car, a completely new brake pedal assembly may not be necessary, but when you’re getting serious about performance and braking, many of the aftermarket assemblies will provide the strength and adjustments needed. There are assemblies that mount to the floor or the firewall and have adjustments to position each pedal exactly to fit your needs. Having the pedals closer together and on a single plane will provide a much better driving and braking experience.
Also, moving to a new pedal assembly provides more alternatives and solutions for mounting the master cylinder(s). Aftermarket pedals are designed to accept remote master cylinders or even dual units (one for the front, one for the rear) that provide increased adjustments for pedal feel and braking bias between the front and the rear. For those applications, an entire assembly for the throttle, brake, and clutch will be in your future and would be a wise investment.
Brake Fluid and Hydraulics
The brake system is like a mini hydraulic network with plumbing to each wheel running up to a common point: the master cylinder. The brake pedal uses mechanical lever-age to exert force onto the pushrod and piston of the master cylinder, which pressurizes the fluid in the lines and against the pistons of the calipers or wheel cylinders.
Wilwood offers a list of pedal assemblies for street cars through sprint cars. This example is built with a clutch pedal and allows the master cylinders (hydraulic clutch too) to be mounted inside the firewall. (Photo Courtesy Wilwood Engineering Inc.)
The small piston and area within the master cylinder can move a larger piston (like in the caliper) with more force, albeit a shorter distance. Think of it like a floor jack and how big of a stroke is needed with the handle to move the lifting mechanism.
Pedals and pedal pads can dress up the interior and put your own personal touch in your pride and joy. This could be the perfect companion to a disc brake upgrade to your classic muscle car. This set is from Billet Specialties.
Pedal Pressure
Knowing the pedal ratio (mechanical leverage) of the brake lever will allow the amount of force required to activate the brakes to be increased or decreased. By varying the pedal ratio, the brake pressure can be adjusted without changing the amount of pressure applied by foot. The trade-off is that the amount of lever movement necessary will change.
To calculate the pedal ratio, measure the distance from the pivot point of the brake lever to the middle of the pedal push point and divide that by the distance from the pivot point to the pushrod connection (A / B = PR).
A: The length of the pivot point to the center of the pedal
B: The length of the pivot point to the master cylinder pushrod
PR: Pedal Ratio
Example: A is 5 inches, and B is 1 inch, so the ratio is 5:1.
By adjusting the lengths, the brake force can be increased/decreased