Types of Brake Rotors in Cars
Brake rotors play an essential role in the braking system of automobiles. They provide a smooth surface for the brake pads to clamp onto when pressure is applied, allowing the wheels to slow down or stop. The friction between the brake pads and rotors is what brings a moving vehicle to a halt.
All modern cars, trucks, and SUVs use either disc brakes or drum brakes. Disc brakes have a rotor attached to the wheel hub that spins along with the wheel. Drum brakes have curved brake shoes that press against the inner surface of a drum attached to the wheel. In both cases, the rotors and drums provide the friction surface needed to stop the vehicle.
Having properly functioning brake rotors is crucial for safe driving. As the main component that interacts with the brake pads, worn, warped, or cracked rotors can lead to poor braking performance, longer stopping distances, and a loss of brake control. Keeping brake rotors in good operating condition ensures smooth, even braking power when you need to slow your vehicle.
Disc Brakes
Disc brakes work by squeezing brake pads against a metal disc (or rotor) attached to the wheel hub in order to slow or stop the vehicle. When the brake pedal is pressed, hydraulic fluid in the brake lines applies pressure to calipers containing brake pads. The calipers then clamp down on the rotor on both sides, creating friction that slows the wheel’s rotation.
Disc brakes have several advantages over other brake types like drum brakes:
- Better heat dissipation – The exposed rotors allow air to circulate and cool the brakes, reducing fade.
- Less affected by water – Disc brakes perform well even when wet unlike drum brakes.
- Self adjusting – Disc brake pads automatically adjust as they wear down.
- Higher friction – The brake pads make full contact with the rotor surface for effective braking.
- Longer life – Disc brakes tend to last longer before needing replacement.
Overall, disc brakes provide stronger braking power, more consistent performance, require less maintenance, and have a longer lifespan compared to other brake types (The Advantages of Disc Brake Road Bikes). This makes them ideal for high performance vehicles.
Drum Brakes
Drum brakes work by pressing brake shoes lined with friction material against the inner surface of a rotating drum. When the brakes are applied, the brake shoes are forced against the drum, slowing the vehicle by creating friction. This friction generates heat, which can lead to brake fade if the drums overheat.
Drum brakes have some disadvantages compared to disc brakes:
Drum brakes are prone to overheating and fade. The enclosed drum provides limited cooling compared to disc brakes (Source).
Drum brakes can be affected by water. When wet, their performance is reduced until they dry out. Disc brakes are less impacted by water (Source).
Drum brakes have more complex mechanical components than disc brakes. This can make maintenance and repairs more difficult and costly.
Drum brakes lack the stopping power of disc brakes due to their smaller friction surface area.
Vented Rotors
Vented rotors, also known as ventilated or perforated rotors, have small holes or slots drilled into the braking surface. These holes serve to provide airflow through the rotor, allowing heat to dissipate more quickly than solid rotors during heavy braking. The improved cooling provided by vented rotors helps prevent brake fade, which is a reduction in braking power due to overheated components (Source).
Compared to solid rotors, the key benefits of vented rotors include:
- Better heat dissipation and resistance to brake fade
- More consistent braking power during prolonged use
- Reduced risk of warping under high heat
- Increased pad and rotor life due to cooler operating temperatures
The open design of vented rotors makes them a popular upgrade over stock solid rotors for performance driving applications. They can handle repeated heavy braking without loss of performance. For normal street driving, vented rotors may still offer advantages for larger vehicles like trucks or SUVs. Overall, vented rotors provide superior cooling properties over solid rotors in demanding braking conditions.
Slotted Rotors
Slotted rotors have a series of straight grooves or slots cut into the surface of the rotor. The purpose of the slots is to allow heat, gas, and dust to escape from between the rotor surface and the brake pad (1). This improves heat dissipation and helps prevent brake fade during repeated hard braking. The slots also help wipe away debris from the pad surface, preventing uneven deposits from building up on the rotor over time.
Some of the pros of slotted rotors include (2):
- Better heat dissipation and resistance to brake fade
- Self-cleaning action keeps pad and rotor surfaces clear
- May provide some extra bite and braking power in certain conditions
However, slotted rotors also come with some downsides, such as (3):
- Can be noisy, producing a high-pitched scraping sound
- Rotor slots are stress points that can crack over time
- May wear brake pads faster compared to blank rotors
- More difficult to resurface rotors due to uneven wear
Overall, slotted rotors offer improved performance through better heat management, but have shorter lifespan and can increase noise and pad wear compared to blank rotors.
Cross-Drilled Rotors
Cross-drilled rotors have small holes drilled perpendicular to the surface of the brake rotor. The purpose of cross-drilling rotors is to allow gases and dust to escape through the holes during braking, which improves heat dissipation. This is intended to reduce brake fade at high temperatures.
The pros of cross-drilled rotors are:
- Better cooling and heat dissipation to reduce brake fade
- Less gas and dust buildup on the rotor surface
The cons of cross-drilled rotors are:
- Can be prone to cracking over time, especially on high performance vehicles
- More expensive than blank rotors
- Can cause additional noise and vibration
Overall, cross-drilled rotors offer better performance under hard braking, but have a shorter lifespan compared to blank rotors. They are best suited for track cars or high performance street use rather than daily drivers.
Cryo-Treated Rotors
Cryo-treated rotors undergo an extreme cooling process called cryogenic treatment. During cryogenic treatment, rotors are frozen to temperatures below -300°F using liquid nitrogen or helium (Source). This freezes the metal at a molecular level, helping realign and strengthen the molecular structure.
Proponents of cryo-treatment for brake rotors claim it provides several benefits:
- Increased rotor life due to enhanced wear resistance
- Reduced warped rotors and cracking
- Decreased vibration and noise
- Lower rates of rotor replacement needed
However, some experts debate the benefits of cryo-treating brake rotors, so buyers should consider whether the extra cost is worthwhile for their needs (Source).
Ceramic Brake Rotors
Ceramic brake rotors are made from ceramic fibers that are molded together using high heat and pressure. They are significantly lighter than traditional iron rotors which reduces unsprung weight. Ceramic rotors are also able to withstand higher temperatures which improves braking performance and reduces brake fade.
Some of the pros of ceramic brake rotors include:
- Excellent heat resistance which reduces brake fade
- Lower unsprung weight which improves handling and suspension response
- Resistance to corrosion and rust
- Long service life with less wear
- Quieter braking with less noise and vibration
However, there are some downsides as well:
- More expensive cost compared to iron rotors
- Can crack or shatter if impacted incorrectly
- Require special brake pads designed for ceramics
Overall, ceramic brake rotors offer improved braking performance and durability for drivers who do repeated heavy braking, such as on a racetrack. But the higher cost means they are not practical for most street use. Care must also be taken to use compatible ceramic brake pads.
Carbon-Carbon Rotors
Carbon-carbon rotors are made from carbon fiber rather than traditional cast iron or steel. They are extremely lightweight yet able to withstand intense heat and friction (Source). Carbon-carbon rotors were originally developed for aerospace and Formula 1 racing applications where minimizing weight and maximizing braking performance are critical (Source).
Compared to traditional rotors, carbon-carbon rotors provide superior stopping power and fade resistance. However, they are also significantly more expensive. As a result, carbon-carbon rotors are primarily found on high-end sports cars and race vehicles where the utmost braking performance is required.
For road cars, carbon-ceramic rotors are more common as they offer a compromise between performance, longevity, and cost. But for applications where weight savings and fade resistance are paramount, carbon-carbon remains the gold standard in brake rotor technology.
Buying Considerations
When it’s time to replace your brake rotors, there are several factors to consider in choosing the right ones for your vehicle and driving needs:
Rotor thickness: New rotors often range from 0.39 in to 0.98 in thick. Thicker rotors tend to last longer before needing replacement. Consult your owner’s manual for the minimum safe rotor thickness for your vehicle make and model. Going below this spec can cause braking issues. Use a micrometer to measure rotor thickness if unsure.
According to CarParts.com, the average minimum safe thickness for most vehicles is around 0.3 in to 0.4 in.
Rotor type: The main types to choose from are blank, drilled, slotted, and dimpled rotors. Blank rotors are the most common and affordable choice for everyday driving. Slotted, cross-drilled, and dimpled rotors are mainly for performance vehicles and driving. They dissipate heat better but produce more dust.
Brand: Trusted brands like Brembo, EBC, Power Stop, Bosch, and Akebono generally make high-quality rotors that justify their higher price. Less expensive store brand rotors can be hit or miss on longevity and smooth braking performance. Check reviews to compare different brands’ rotor lines.
Coating: Some rotors feature protective coatings like zinc, silicone, or black E-coating to prevent rust and corrosion. These help rotors last longer in wet climates but add cost.
Cryo treatment: This deep freezing process can strengthen metals and improve rotor longevity. Most manufacturers offer cryo-treated rotors for a small upcharge.
Consider your driving conditions, braking needs, budget and expected mileage before choosing new rotors. Higher performance rotors often cost more but can provide better braking power and longevity for enthusiastic drivers.