Rotors take a beating under...
Rotors take a beating under intense braking, as shown by the glowing disc in the photo. The sparks flying out are shards of pad material.
This brake tech guide was written to help you decide which avenue to go down in regard to your Pontiac's brake upgrades. We've talked with some of the biggest names in the performance disc-brake industry, including Brembo, Stoptech, and Wilwood, as well as Master Power Brakes. For Part I, we discuss rotors because there is a lot of ground to cover here. Part II will examine friction materials (pads), calipers, and fluids.
In operation, the brakes slow the rotation of the wheel and tire by converting kinetic energy into thermal energy, thus producing heat. The quest for braking performance involves the braking system's efficiency in dealing with heat and its ability to convert energy. The role of the tires in the braking process cannot be understated, however, as maintaining their grip on the pavement is paramount to stopping your Pontiac.
Before upgrading your brakes, there are a few important factors you should consider: namely, your budget, intended use, and driving style.
Most factory brake systems are designed for competent stopping when cold or hot, and quiet operation. In many cases, these components are not intended for severe use and repetitive stops with great kinetic energy. That doesn't mean you have to buy a six-piston-caliper setup with two-piece rotors. There's a good chance that a simple fluid, pad, lines, and rotor upgrade, like we performed on our '05 GTO, will bring your Pontiac into stop-on-a-dime territory.
This is a basic ventilated...
This is a basic ventilated rotor.
The brake disc, or rotor, is the surface that is contacted by the pads. When the brakes are appled, abrasive friction is prevalent during lower temperature braking. It's simply the friction caused by the pads rubbing on the surface of the rotor. When temperatures rise, adherent friction comes into play, which is the process by which a thin layer of brake-pad material is transferred onto the rotor surface. This layer of pad material is what rubs on the brake pad.
Each type of friction allows for conversion of kinetic energy into thermal energy. Abrasive friction, as you may imagine, physically wear the rotors more quickly than adherent friction, but the latter will generally be tougher on the rotor thermally, which leads to heat cracking.
The metallurgy of the majority of rotors is comprised of several grades of cast iron. According to Emanuele Bruletti, Brembo's North American engineer, cast iron is a known metal with stable heat properties, and therefore a good candidate for rotors. The downside to the material is that it's very heavy, which has prompted manufacturers to make rotors out of lighter materials, such as lighter steel, aluminum, titanium, carbon/ceramic, and carbon/carbon. Even among the same materials, there are many rotor configurations available, either off-the-shelf or custom-tailored to your vehicle.
Ventilated rotors are the...
Ventilated rotors are the only option for a performance braking system. The interior design of the rotor allows air to pass through it, helping to cool the friction surface and the overall braking system. We are showing three different types of cooling vane designs.
Since the rotor receives the most thermal energy, or heat, it's very important to control this heat effectively. The use of vented rotors has become more common because the rotor itself features internal cooling passages that work like an impeller. When it spins, air is pulled through the "eye," or center, and is evacuated through the outside of the rotor. A downside to this is the resulting radiant heat-in other words, the rotor will actually heat everything surrounding it.
A vented rotor should be the only choice for a performance brake system, since a solid rotor must rely solely on ambient air to control temperature, while the vented rotor is continually moving air through it to better control heat. More air moving across the surface or through the rotor results in increased cooling ability.
Race cars and some street cars benefit from extensive use of brake-cooling ducts to draw cool air onto the rotor surface or rotor eye. This can lower temperatures as much as a few hundred degrees, allowing the brakes to perform better.
"When we set up a brake system for a customer on a race team, brake cooling ducts are fundamental," says Emanuele. "We ask them to focus on the cooling, because cooler rotors allow everything to perform better."