Disc brake rotors (aka 'rotors') are the actual discs that brake pads clamp onto, creating friction that slows a vehicle. Disc brake rotors bolt on over the axle hub and contain holes that allow wheel mounting bolts to pass through and rotate with the wheels. Since there are many rotor styles and designs specially created for every budget and need, we've listed the advantages of each disc brake rotor so that you can make the right choice and get the best for your vehicle. All rotors, except ceramic brake rotors and two-piece rotors with aluminum centers, are typically one piece and crafted from iron for maximum heat absorption.
As a rule, OEM style rotors are standard equipment on most vehicles, and are also the most basic style available. As opposed to performance-oriented rotors, the OEM ones have a smooth pad contact surface with no grooves or holes for heat dissipation. Same as more expensive rotors, most OEM style front rotors are vented: they have a vented center between both rotor sides as well as straight, parallel fins to improve the passage of air. This ensures metal expands more evenly, minimizing the chance of warping. Depending on the make and model, rear disc brake rotors are either vented, or 'solid' with no cooling space between rotor sides. By and large, solid rotors are adequate for rear applications because less of the work stopping the vehicle is done there and they don't heat up as much. For those who are going to use their vehicle for everyday driving rather than aggressive road racing, basic OEM style rotors are just the ticket.
'Slotted' (aka 'grooved') rotors are designed for the enthusiasts who expect low noise from the brakes while having greater level of aggressive driving or towing. Two sets of indented, shallow slots across both rotor sides allow water, heat, brake dust, and friction gases to slide out a lot easier from underneath the pads. They stay cooler during aggressive driving and are perfect for 4WDs that often haul heavy loads or tow trailers because the slots are not deeply cut into the rotor. As a result, the rotor retains its mass and strength without fracturing or warping under heavy-duty use. Considering that these slots slice away more pad material on contact, it's fairly typical for this type of rotor to have slightly lower pad life.
'Drilled' disc rotors are definitely a step ahead from slotted ones when it comes to high performance driving. Most drilled rotors feature holes that reach through to the other side – a layout that ensures maximum disbursement of heat and debris generated under heavier use. Some drilled rotors may as well have a slotted design, and both of these are great for use on performance vehicles that are typically driven hard. A disadvantage of drilled rotors appears right when those are used on a vehicle that takes on a greater weight load due to hauling of heavy cargo or sustained towing. Vehicles with built-up engines or superchargers can also have a damaging effect on drilled rotors, especially when abused by either stunt driving or drifting. Since the drilled holes take mass out of the rotors, cracks are likely to occur between the perforations.
Rotor surfaces with holes that have been partially drilled through are also known as 'dimpled'. While they reduce the risk of cracking, dimpled rotors sweep away less heat than fully-drilled ones do.
In spite of brake rotor surface design, there are variations within ventilated centers between rotor sides. Some performance-oriented brakes have curved cooling fins instead of straight, parallel ones. Because curved fins only function efficiently in one direction, this rotor type is labeled unidirectional and feature opposite designs for right and left sides. Other styles of ventilated rotors may feature tear drop-shaped pillars between rotor sides instead of fins to create more metal contact and ensure better heat dissipation with the same airflow.
If you're looking to achieve quicker brake response, 'two-piece' rotors are exactly what you need. Two-piece parts feature an aluminum center section bolted to a traditional iron outer section for solid pad contact. Because the center section is aluminum, a lot of weight is saved. It's hard to confuse a two-piece rotor with anything else because bolts that lock the two pieces together are highly visible, and center sections usually have a different-colored finish in order to heighten their appeal. Two-piece rotors are more expensive and are typically available on high performance vehicles. If that's not an issue, they are great for offsetting the heavier weight of larger wheels and tires.
'Ceramic' rotors (aka 'carbon ceramic') are not made of iron, but a special blend of porcelain compound materials. First used on the production version of Porsche's 2001 911 GT2, their popularity as original equipment on high-end performance models has steadily grown. Ceramic brakes are great options as they are corrosion resistant, have better stopping power, and withstand heat far better than iron parts do. In fact, availability of aftermarket ceramic brakes is lower than any other kind because their high cost and associated exclusivity puts them in the 'unique' category.
Finishes on rotors can vary as well. Since iron is not subject to corrosion, most such rotors are coated with some form of anodizing, paint, or powder coat to keep rust at bay on areas that don't see pad contact. No rotor will stay nice-looking for a lifetime, but a sure bet for vanity is a two-piece rotor with a corrosion-free aluminum center section.