Power Stop makes both slotted and cross-drilled rotors but there are distinct advantages to drilled rotors which is why many vehicles (Corvette, Porsche, Ferrari, etc.) come equipped with drilled rotors. Your stock brake rotors can exceed 1,000 degrees F where many friction compounds start to break down. The high temperature can also lead to annoying brake pulsation and a shaking steering wheel. Drilled rotors are engineered to keep your brakes cool, so your brake pad has improved pad bite with reduced fade. Drilled rotors can operate up to 200 degrees cooler than slotted rotors to protect against rotor warping. While a slotted rotor does a good job of removing gas and dust generated by the friction pad, it does not cool your brakes. Improvement in brake output from drilled rotors is the subject of SAE paper 2006-01-0691 "The Effect of Rotor Cross Drilling on Brake Performance." In a nutshell, for street and highway driving, drilled rotors are typically preferred. For track, autocross, towing or other severe duty applications, slotted rotors are recommended.
Brake pads contain various metals and minerals that are bound together using a resin. At high temperature, this resin turns to liquid and can bleed out onto the rotor. Glazing is dangerous because it prevents normal contact between the pad and the rotor so you lose pad bite. Glazing can also cause brake pulsation most commonly called "rotor warping." Drilled rotors prevent pad glazing as reported in SAE paper 2006-01-0691. This is one of the reasons why drilled rotors provide 12% to 37% more brake torque over stock rotors.
Pad bite is called the coefficient of friction. At high temperatures, all brake pads have a reduced coefficient of friction. This is called brake fade. Power Stop engineers all of their friction compounds to resist brake fade. This assures safe, consistent stopping power. Different grades of pads will have different fade characteristics. The Z36 pads are by far the most fade resistant pad that is commercially available.
All rotating objects have vibration. This vibration can become amplified at specific natural harmonic frequencies. Have you ever noticed a little vibration in your car as you travel at a certain speed on the highway, and then it goes away as you go a little faster? The wheels were passing through one of these harmonics. Brake noise is caused by vibration primarily from the rotor, pad and caliper. The causes are complex and include things like the compressibility of the brake pad, the surface finish of the rotor, the stick-slip oscillation at certain temperatures, rotor dimensional run-out, rotor harmonic frequency and many other factors. Noise attenuation is a complex part of friction development. Power Stop Evolution and Posi-Mold pads feature dual active rubber coated constrained layer shims. The rubber is placed on both the pad side and caliper side of the shim. This helps reduce vibration that can be transmitted from the pad to the vehicle. Noise can be reduced by putting a silicon based material on the back of the plate where the caliper piston makes contact. It is also important to turn the rotor and make sure the rotor flange is parallel to the hub mounting surface. One sure fire way to make noise is when a pad overhangs the edge of the rotor or encroaches on the groove between the rotor hat and smooth flange surface. It is important that you check how the pad seats on the rotor when you change the brakes.
The term "warped rotors" is commonly used to describe brake pulsation, but the rotor is not actually warping at high temperature so the term "warped rotors" is not accurate. The primary cause of brake pulsation is from uneven friction deposits on the rotor. As the brakes get hot, friction material from the pad is deposited as a very thin layer on the rotor. If you come to a hot stop and clamp your brakes down, the pad continues to deposit material on one spot. As you continue to use the brakes, this high spot on the rotor will get hotter than other parts of the rotor. When the temperature starts to exceed 1150 F, the crystal lattice structure of the iron can change into a very hard, brittle material called cementite. Your brakes can hit 1100 F or higher coming off a highway ramp with severe deceleration. Hard spots start to form, and it doesn't wear down like the rest of the rotor. The hot spot nodules will not dissipate heat as well as the neighboring material, so it gets hotter than the rest of the rotor and causes the spot to grow. The result is a permanent high spot that you feel as pulsating brakes. You can try to turn down the rotor, but chances are the nodule is bigger than the cut depth on the lathe. So it is just a matter of time before the pulsation will come back. However, you can prevent brake pulsation two ways: 1) use a high quality, properly drilled rotor to keep the temperature low, and 2) don't clamp down on your brakes after a hot stop!
In order of effectiveness: 1) Get really good tires that grip the road, 2) select the right brake pads with a high coefficient of friction, 3) use cross-drilled rotors to improve convection heat transfer.
IMPORTANT: BREAK IN NEW BRAKE PADS/ROTORS USING THE PAD BEDDING PROCEDURE AS FOLLOWS. PROPER PAD BEDDING CAN PREVENT ROTOR WARPING.
The break in procedure is critical to brake performance. The reason for a proper break in is to establish an even layer of friction material deposited on the rotors from the brake pads. It is very important that this initial layer of friction material is evenly distributed. Break in the pads as follows: 5 moderate to aggressive stops from 40 mph down to 10 mph in rapid succession without letting the brakes cool and do not come to a complete stop. Then do 5 moderate stops from 35 mph to 5 mph in rapid succession without letting the brakes cool. You should expect to smell some resin as the brakes get hot. After this is complete, drive around for as long as possible without excessively heating the brakes and without coming to a complete stop (Try for about 5 minutes at moderate speed). This is the cooling stage. It allows the heated resin in the brake pads to cool and cure. After the brakes have cooled to standard operating temperature, you may use the brakes normally.
Please avoid using DOT 5.0 synthetic fluid unless specifically recommended by the vehicle manufacturer. Some synthetic fluids can cause rubber piston seals to break down. Power Stop recommends replacing brake fluid on every pad change with a DOT 3.0 or 4.0 fluid as specified in your owner's manual.
Power Stop does not recommend turning down the rotors. However, drilled or slotted rotors can be machined using a sharp bit and very light cuts (to prevent bit skipping near the holes). Under no circumstances should a rotor be turned below the hole chamfer depth.
The silver or gold zinc dichromate plating will be removed by the brake pad contact. So the area underneath the pad will be natural gray iron after the first few stops.
The purpose of painting or plating a rotor is to resist corrosion. Rotors can get hot, more than 1,000 F. At these temperatures, paint will peel or burn off. Zinc-dichromate plating is more expensive but it lasts much longer and keeps the rotors looking new for a long time.
The term Thermal Scorched brake pads refers to the curing of the first millimeter of the brake pad material in an oven. This process actually simulates a professional high-speed break in procedure used by professional mechanics and race teams. It heats the surface of the friction material to a very high temperature, which cures the compound and makes sure it is 100% ready to perform. This process makes the coefficient of friction consistent and predictable right out of the box; it also prevents pad glazing. Many manufacturers do not go through this extra step, but Power Stop knows the importance of proper break-in of new brake pads, so they make sure that the pads are thermal scorched during the production process.