Brake Rotors: Drilled, Slotted, Carbon-Ceramic

A rotor looks like a simple metal disc, but the material and surface design change how it handles heat, wear and noise. Here is what the common types are and what each one trades away.

What are most rotors made of?

Most passenger-car rotors are made of cast iron. It is a proven material that grips well with ordinary pads, absorbs a lot of heat and is relatively easy to manufacture. Some vehicles use a two-piece design, where an iron friction ring is attached to a separate center section, often made of aluminum.

Rotors also come in two basic shapes. A solid rotor is a single disc. A vented rotor has two friction surfaces with vanes between them, so air can flow through and carry heat away. Vented rotors are common on the front axle, where most of the braking work happens, while solid rotors are often used at the rear of lighter vehicles.

What do holes and slots do, and what do they cost you?

Drilled rotors have holes through the friction surface. They can help release gas, water and dust and they reduce some weight. The trade-off is that the edges of those holes can become starting points for small cracks when the rotor goes through repeated heavy heating and cooling.

Slotted rotors have shallow grooves cut across the surface. The slots give dust and debris somewhere to go and keep the pad surface fresh. The trade-off is that they can wear pads faster and may be noisier than a plain surface.

What are carbon-ceramic rotors and who uses them?

Carbon-ceramic rotors are made from a composite of carbon fibers and ceramic material rather than iron. They are much lighter than iron rotors and are designed to handle very high temperatures. They are usually found as factory equipment on high-performance vehicles.

They are built as a matched system with specific pads, and they are not a bolt-on upgrade for an ordinary car. Their different construction also means they are usually not interchangeable with standard iron rotors.

Which rotor is right for a commuter?

For daily driving, the right match is usually the rotor type your vehicle was designed to use, paired with pads suited to it. Plain iron rotors are quiet, predictable and work well with common pad materials.

If you are considering something different, tell the technician how you drive, including traffic, hills and any towing. They can look at what is on your car now and explain what makes sense for it.