It’s not necessary to go fast in a straight line to understand how important brakes are in classic muscle cars. Driving in congested traffic on today’s highways is proof that disc brake upgrades are not only desired but also a necessity.
A muscle car is at a severe and unhealthy disadvantage when jousting for lane position with much lighter modern cars that are equipped with high-performance brake systems. Even if there is no intention of putting your classic car on an autocross course, drag strip, or in a street race, a conversion from drum brakes to disc brakes is a wise move not only for you and your family but also for others on the road.
Once the upgrade to performance braking has been decided, a few more decisions need to be made. Do you convert the front drum brakes to a disc brake system and leave drums on the rear? Perhaps you are looking to do some autocross events and want to upgrade the front and rear to disc brakes. Maybe you want to take your car to a car show where you want to compete for a builder’s award. More often than not, vintage muscle car owners simply want to perform a budget disc brake upgrade for their daily driver.
This Tech Tip is From the Full Book, MUSCLE CAR BRAKE UPGRADES: HOW TO DESIGN, SELECT, AND INSTALL. For a comprehensive guide on this entire subject you can visit this link:
SHARE THIS ARTICLE: Please feel free to share this post In Facebook Groups or any automotive Forums or blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link:
One of the first considerations in any upgrade is budget. How much do you want to spend on your brake system upgrade? Partial kits, such as a front brake upgrade, can range from $600 to thousands, depending on the caliber and performance level of the components. Fortunately for car enthusiasts, most muscle cars made in the 1960s and early 1970s had very few variations within the nameplates. This means that special-option muscle cars with front disc brakes may be available in wrecking yards or replacement parts can be found off the shelf.
The most common muscle car brake upgrade attempted by home garage builders is the OEM-style drum-to-disc replacement kit, such as this one from Classic Performance Products (CPP). CPP manufactures a full line of brake and suspension components for Ford, General Motors, and Mopar cars.
For example, GM’s Chevelle and Malibu models were manufactured with the same style of brake master cylinders, and even rotors were the same size from 1964 to 1969. Very few of these cars were built with front-wheel disc brakes. Hunting through wrecking yards for these rare cars will probably not result in much gain, but OEM replacement parts are affordable from several sources.
Even if you were to find the parts you need, the best of 1960s brake technology was mediocre at best. Brakes were not huge considerations in automotive engineering in the muscle car era. Tires and brake pad material were limiting factors. Fifty-year-old technology is still not going to be safe on today’s highways surrounded by vehicles with present-day stopping power.
Many manufacturers use GM factory C5 Corvette calipers in their brake kits for the single-piston, sliding-type caliper. This is not true of the CPP calipers that use 52-mm pistons. The C5 Corvette calipers use a 40-mm piston. CPP’s calipers also have larger pad surfaces that the company says offer nearly 50 percent more stopping power than the C5 calipers. Price-wise, the CPP calipers cost far less than a factory C5 Corvette caliper; plus, they have iron bodies that are more rigid, resulting in a firmer pedal.
Researching and finding a source for OEM-type disc brake conversions could possibly lower the overall cost of an upgrade, providing you are willing to spend the time to find the most cost-efficient components, but the project will most likely be complex.
OEM parts are usually readily available at your local parts store or Amazon. However, there is also a good possibility that you may need more components in an OEM-type conversion, such as different spindles, brake pedal assemblies, power boosters, combination valves, lines, etc.
Fortunately for muscle car enthusiasts, a number of aftermarket brake companies make brake kits for almost every possible car and application. Many of these are plug and play or bolt on and go.
Companies such as Baer Brakes, Classic Performance Products, Master Power Brakes, Stainless Steel Brakes Corporation, and Wilwood have spent considerable time and resources developing brake kits that are simpler than trying to piece together individual components, and in most cases they are more economical as well.
Performance braking is more than just brakes. For the best braking function, the builder must also consider tires, suspension, wheelbase, and driving style. To get the maximum braking potential, low center of gravity, proper rear weight bias, and corner weight balance should be optimized.
Wheel Fit and Tires
Brake expert Bill Fowler, a former vice president of development at Baer Brakes, helped define the decision-making process.
“The first real questions to answer are: What are your intentions with the car, and what wheel and tire package will you be using?” Tires are a huge consideration because this is actually where the braking happens. The brakes slow the rotation of the tires and the braking ability of the tires is dependent on the tire compound.
The most critical factor is the size of the wheel,” Fowler added. “Even when the manufacturers began offering the single-piston front calipers on muscle cars, wheel size constraints left the engineers using smaller calipers so the braking force did not have an immediate impact.”
Most early muscle cars from the 1960s and early 1970s were produced with 14-inch wheels. Using these stock wheels minimizes the size of caliper that can fit inside the wheel. Caliper size is directly proportionate to braking force.
Prior to installing the brake kit onto the vehicle, put the rotor and hub together and check the fit inside the wheel you plan on using. Check for clearance. If it doesn’t have enough clearance, you can send it back because technically, it hasn’t been installed on the car.
“It’s all about leverage,” said Fowler, “like a larger-diameter steering wheel, or the difference between a 3/8-inch drive ratchet and a 1/2-inch drive ratchet.”
According to most of the leading brake experts in the industry, a 15-inch tire is the minimum size for any performance braking system on muscle cars. Backspacing, tire tallness, diameter, and width are all braking considerations. The only downside to larger rotors is that stock wheels won’t allow for the extra space. Tires and wheels are an area where it pays to plan ahead and get the size that is correct for the desired application and braking requirements. This is the starting point for any chassis build because this is the one thing you can’t make or easily have custom made. Some companies offer low-profile calipers so you can run the largest rotor behind a smaller wheel, which is one option for enthusiasts looking to upgrade their brake system and still use factory-style wheels.
Floating calipers, such as this one produced by CPP, have proven themselves as very safe daily driver choices. Manufacturing processes have changed and these units are very well built with greater technology than the original 1960s units. There are even color options that were not even an afterthought in the muscle car era.
It is generally accepted that there are two basic types of brake calipers. The first is often referred to as the floating or sliding caliper. Floating calipers attach to a solidly mounted caliper bracket. The caliper itself is not solidly mounted and is allowed to slide left and right on pins and bushings that are mounted on the bracket.
When the driver steps on the brake pedal, the piston on the inner side of the caliper is actuated by the hydraulic pressure and pushes the brake pad out to the rotor. Because the rotor is solidly mounted and can’t move side to side, the caliper is forced to slide until the brake pad from the other side contacts the rotors. The clamping force of the two brake pads slows down the rotating disc (rotor).
Because there are fewer parts in a floating caliper assembly, it is usually compact, lighter, and less expensive to make or purchase. These are major advantages of the floating brake caliper. Maintenance is simple and brake pads can be changed quickly and easily.
The second type of automotive brake caliper is a fixed caliper. Unlike the floating caliper, the entire caliper is solidly mounted in the fixed caliper system. Each side of the caliper has one or more pistons that push the brake pads to the rotor. Fixed calipers normally use multiple pistons with the same number of pistons on both sides of the caliper. These are usually configured in two pistons (one on each side), four pistons (two on each side), or six pistons (three on each side).
The most significant advantage of the fixed caliper system stems from the amount of clamping power that can be applied evenly to both sides of the rotor. Because the clamping force is applied evenly, fixed calipers are said to provide better feedback and feel back to the driver through the brake pedal. This has made the fixed caliper brakes popular in modern luxury and performance cars. These have become a popular conversion or upgrade for cars from all eras.
In complete fairness to both styles of calipers, a floating caliper can offer much of the same performance of a fixed caliper at a lower price for many applications that are not high performance. The real difference shows up in high-performance and race conditions. The trade-off for this higher performance is cost and more frequent pad replacement and maintenance.
Deciding Which Caliper Type to Use
Both types of disc brake calipers are merited and can be used to make an effective braking system for autos from the muscle car era. The lightweight and inexpensive cost of floating caliper brakes makes them popular among many car enthusiasts. Muscle cars used as daily drivers are often treated to a floating caliper disc brake conversion from the stock drum brakes. These conversions are efficient and work well even among modern compact cars in heavy traffic.
Highways full of lighter vehicles with modern braking technology pose a safety concern for heavier, mid-1960s muscle cars with drum brakes. At bare minimum, an entry-level floating caliper upgrade should be considered.
If the vehicle to be upgraded is built for speed or is a heavier vehicle with decent amounts of speed, a higher-performance braking system is required. Low-cost systems probably won’t have the clamping force needed to stop these types of cars safely. A fixed caliper would be a great choice for this application.
Some vehicles are built with a proper balance of weight and speed that can handle fixed calipers on the front wheels and floating calipers on the rear wheels. Some brake manufacturers will provide a kit with this combination if they have tested the components with certain platforms.
Brake Rotor Choices
As we already discussed, the brake rotor or disc is where the kinetic energy to thermal energy conversion takes place. Most brake discs are manufactured from a form of cast iron called “gray iron.” This type of cast iron has a gray color due to the presence of graphite in the compound. It is also the most common type of cast-iron material, used in everything from internal-combustion engine cylinder blocks, to pump housings and valve bodies.
Gray iron has high thermal conductivity and a specific heat capacity that is perfect to make cast disc brake rotors. The Society of Automotive Engineers, now known as SAE International, sets standards for the manufacturing of gray iron. These specifications include the hardness, chemical composition, tensile strength, and other properties for automotive applications.
From stock OEM rotors to many high-performance types, these gray iron pieces are similar, but design plays a huge part in their usage. Some rotors are solid units; others are made with ventilation chambers (most often created during the casting process) running through the disc. These ventilation chambers act to dissipate heat and provide cooling. The size and amount of these ventilation chambers are evaluated for the size, weight, and power of the vehicle, as well as the purpose.
Brake discs often have holes or slots cut through the disc for better heat dissipation, to aid in surface-water dispersal, reduce noise and mass, eliminate outgassing created by the brake pads, and sometimes just for marketing cosmetics.
One thing that most experts agreed on is that there is no such thing as too much brake when it comes to the rotor and calipers. However, there is such a thing as too much brake pressure. Brake disc rotors must be broken in properly to get the best performance and wear correctly.
If the manufacturer has included instructions for bedding in the rotors, follow their instructions. This physical bedding-in will include some moderate to heavy stops followed by a cooling period. This should be repeated several times until the rotor has been tempered to prevent thermal shock, distortion, or the formation of hot spots. Don’t skip this step; it is worth the effort.
Written by Bobby Kimbrough and republished with permission of CarTech Inc
LEARN MORE ABOUT THIS BOOK!
If you liked this article you will love the full book!