We have compiled what we think is critical information about racing brakes and their application. We talked to many manufacturers and experts and this is a summary of those conversations. So as to not put an advertising face on this piece, I have left out the names and companies. Our goal is to educate you, the racer, so that you can approach your brake selection and tuning more efficiently. Let’s get started.
How do I choose brake pads for my type of racing?
Pad choice is largely determined by the type of car and racetrack. Most brake experts realize that we need to consider the type of car we are racing as to weight, center of gravity height, and size of the tire contact patch as well as the amount of grip that the track provides. We don’t want to overwhelm the tire with too much brake grip.
Because of the large selection of brake pad materials and grip levels, you should probably contact a brake pad manufacturer, chassis builder or performance parts distributor who can help eliminate guess work to get a better understanding of brake pad performance characteristics.
Does front-to-rear pad size matter?
Racers are often faced with decisions on how to regulate the brake bias between the front and rear. We need to know a little about pad sizes related to creating brake bias. When increasing the contact surface area of a pad, additional stopping performance can be attained. Many caliper manufacturers offer calipers designed for different size pads yet still allow for the caliper to mount in the same location. This allows teams to change calipers and pad size without having to change the mounting bracket and location. However, most chassis builders choose the pad and caliper combination they feel works best for their particular type of car. When it’s necessary to increase stopping performance, the calipers piston size can be increased or decreased to allow for more or less caliper pressure.
How do I break in my pads?
On the first out lap, most drivers will left-foot brake with stabs on the brake for two or three laps. In the case of prebedding, it must be done in a very controlled environment and is not recommended. While break-in procedure recommendations differ slightly between pad manufacturers, the most important aspect of pad break-in is to slowly bring the pad up to racing temperature followed by a complete cool down cycle with the car parked.
What are some solutions to bias problems?
Understanding the brake bias adjuster function is important. If used correctly the adjuster can aid a driver in many ways. For classes that don’t allow the use of adjusters, using split friction (different brake compounds front to rear) or selecting calipers with different size pistons front to rear or side to side can do a lot to solve performance problems related to bias.
What are some common problem areas during installation of pads?
In our own experience working on our various projects, as we install the brake mounts, we take special care and extra time making sure our caliper mounts were straight and parallel to the brake rotors. This ensures that the pads will be flat against the rotors and all of the surface area will be used when braking.
How long do pads last? When do I change them?
All brake pads are most efficient when they are new. Good-quality pads will perform consistently their whole lifespan. The problems come with improper wear causing pad taper. If the driver complains that the brakes are not working as well as before, change the pads.
What are the different pad materials?
Although every manufacturer keeps its materials list a secret, there are certain givens associated with racing brake pad construction. Raw materials used to produce racing brake pads include many types of metallic and nonmetallic fibers.
The particle size of these fibers plays a big role in the pads’ performance level as well as the wear of the pad and rotor. Carbon-based racing pads have become very popular because they allow for extreme temperature fluctuations while still providing good braking.
Always use pads that were designed for racing, not OE or aftermarket pads that are designed for street use. The design goals for passenger car pads are completely different from the goals for racing—they are not even close to the same. Street pads are designed to operate at lower temperatures, and that combined with an effort to reduce noise and dust makes them useless for racing.
Do pads perform better when they are hot or cold and do I preheat them before qualifying if hot is the answer?
Many fast qualifiers will drag the brake on the outlap to heat the pads. Although most pads are good in a wide range of temperature, often they need to be up to a minimum operating temperature to provide the most grip.
What are the common types of rotors and how do I choose which one is right for me?
Vented brake discs are of course considered better than single-plane discs because of their cooling properties. The discs don’t pump a lot of air through the vents because if they did, we would not see the amount of brake dust that accumulates on the wheel (the rotor would blow it away). The reason why we have curved vanes is because it helps reduce the crack propagation across the disc. It has nothing to do with pumping more air. These designs help support the cheeks (the outer portion of the disc) better. Much study goes into vane design and structure.
When choosing a rotor, you must first determine the available rotor options based on size and mounting. Next, overall weight and cooling vane configurations must be evaluated. For example, rotors with an 11.75-inch diameter and an overall thickness of 1.25 inches, are by far the most popular size used on Late Models and many Modifieds.
Above all, the most important fact to remember is that a larger or heaver rotor that has complete contact with the pad face will allow for better temperature management and longer rotor and pad life, and provide for the most consistent brake feel.
That is why standard cast-iron rotors are still the primary choice of racers in many forms racing. While exotic materials and rotor shapes have been introduced in an effort to reduce the race car’s weight, in most cases the performance of these rotors falls short compared to cast iron.