Disc brakes have revolutionized the world of cycling, offering superior stopping power in many conditions when compared to traditional rim brakes. Integral to the disc brake system are the rotors, which play a crucial role in dissipating heat generated during braking and providing a surface for brake pads to grip. In this article you will have a comprehensive understand of different types of disc brake rotors, especially the difference between 6-bolt and Centerlock rotors.
What are Disc Brake Rotors?
Components and Construction
Material: Disc brake rotors are typically made from durable materials such as stainless steel or lightweight alloys like aluminum. Stainless steel is commonly used due to its excellent heat dissipation properties and resistance to corrosion.
Design: Rotors are circular discs with a flat braking surface where the brake pads make contact. They come in various diameters (commonly 140mm and 160mm for road and gravel bikes) to accommodate different braking needs, with larger diameters generally providing more braking power suitable for applications like downhill mountain biking.
Mounting: There are two primary types of mounting systems for disc brake rotors:
6-Bolt: Uses six evenly spaced bolts to attach the rotor to the hub. This system is widely compatible and allows for easy installation and removal of the rotor.
Centerlock: Utilizes a splined interface that slides onto a splined hub axle and is secured in place with a lockring. This system simplifies installation and is favored for its quick wheel change capabilities.
All of Elitewheels’ road, gravel , MTB, and TT/traithlon wheels have the option for both Centerlock and 6-Bolt.
Braking Mechanism
In addition to the disc rotors, disc brakes have brake pads, calipers, brake levers, and hydraulic fluid and casings or brake cables. When the rider pulls the brake lever, it activates the braking mechanism—pressurizing hydraulic fluid in hydraulic brakes or pulling a cable in mechanical brakes. This force moves the pistons in the brake caliper, which push the brake pads inward towards the rotor.
The pads then squeeze against the rotor’s braking surface, generating friction that slows the rotor’s rotation. As the rotor is attached to the wheel, this friction effectively decelerates or stops the bike. The rotor is designed to dissipate the heat generated during this process to maintain braking performance and prevent overheating.
Key Characteristics
Heat Dissipation
Heat dissipation is a crucial aspect of disc brake rotor design. When brakes are applied, friction between the brake pads and the rotor generates heat. Effective heat dissipation prevents the rotor from overheating, which can lead to brake fade—a reduction in braking performance due to excessive heat. Rotors often feature ventilation holes, slots, or even fins to increase surface area and improve airflow, allowing heat to escape more efficiently. Advanced materials such as high-grade stainless steel or specialized alloys are also used to enhance thermal conductivity and stability under high temperatures, ensuring consistent braking performance even during prolonged or intense braking sessions.
Compatibility
Disc brake rotors must be compatible with the hub and brake caliper specifications of the bike. This includes matching the rotor’s diameter, which ranges from 140mm to 203mm, to ensure it fits within the caliper and provides adequate braking power. The mounting type is also crucial, with the two primary systems being 6-bolt and Centerlock. Ensuring compatibility is essential for proper installation, safety, and optimal braking performance.
Durability
Durability is a key characteristic of disc brake rotors, as they must endure significant wear and heat generated during braking without warping or degrading. High-quality materials like stainless steel provide resistance to corrosion and deformation. Additionally, rotors are designed to distribute braking forces evenly, reducing the risk of localized stress and damage. Some rotors may also have hardened surfaces or reinforced edges to extend their lifespan. Durability ensures that the rotors maintain their structural integrity and performance over time, even in demanding conditions.
Maintenance
Regular maintenance is vital for the longevity and performance of disc brake rotors. This includes periodic inspection for signs of wear, such as thinning or scoring of the braking surface, which can compromise braking efficiency. Cleaning the rotor with specialized disc brake cleaners helps remove dirt, oil, and debris that can affect braking performance. Ensuring proper torque on bolts or lockrings during installation and after use prevents loosening and ensures secure attachment. Maintenance also involves checking the alignment of the rotor to prevent brake rub and uneven pad wear. Consistent maintenance practices help sustain optimal braking performance and safety.
The Benefits of Disc Brakes?
Disc brakes offer several advantages, making them increasingly popular in various types of cycling, from mountain biking to road racing. Here are the key advantages of disc brakes compared to rim brakes:
Superior Braking Power
Consistent Performance: Disc brakes provide more consistent braking power in a variety of conditions, including wet and muddy environments, where rim brakes often struggle.
Increased Stopping Power: The hydraulic or mechanical force applied directly to the rotor offers greater stopping power, especially on steep descents or at high speeds.
Performance in All Weather Conditions
Wet Conditions: Disc brakes perform significantly better in wet and muddy conditions because they are positioned away from the ground and do not rely on rim surface friction, which can be compromised by water and dirt.
Heat Management: Disc rotors are designed to dissipate heat more effectively than rims, reducing the risk of brake fade during prolonged braking.
Less Wear on Wheels
Rim Longevity: With disc brakes, braking force is applied to a rotor attached to the hub rather than the wheel rim, reducing wear and tear on the rims. This extends the lifespan of the wheels.
Greater Tire Clearance
Wider Tires: Disc brakes allow for the use of wider tires because the braking surface is on the rotor, not the rim. This is particularly beneficial for off-road and gravel riding, where wider tires provide better traction and comfort.
Frame and Fork Design: The absence of rim brake calipers allows frame and fork designers more freedom to create structures that accommodate wider tires and enhance overall bike performance.
Enhanced Safety
Less Rim Failure Risk: Rim brakes can overheat and cause the rim to fail, especially on long descents. Disc brakes mitigate this risk by focusing heat generation on the rotor.
Consistency Across Conditions
Temperature Stability: Disc brakes maintain consistent performance across different temperature conditions, whereas rim brakes can suffer from reduced performance in extreme heat or cold.
Less Impact from Rim Conditions: The braking performance of disc brakes is not affected by rim conditions such as being wet, dirty, or uneven.
Are Disc Brakes the Best Choice
Temperature Stability: While disc brakes have become increasingly popular, it doesn’t mean that they are the best option for everyone. Rim brakes have their own benefits as well.
Cost: In general, rim brakes are less expensive to manufacture. This cost is passed onto the consumer.
Ease of Maintenance and Installation: Rim brakes and mechanical disc brakes are much simpler to maintain, as they do not rely on hydraulic fluid to work.
Control: While disc brakes can make braking easier in all conditions, when a surface is wet, applying disc brakes especially on the rear wheel can cause fishtailing, reducing stability. Rim brakes often do not brake as well in the wet. While this increases stopping distance, it reduces the risk of losing control and fishtailing.
Weight: Rim brakes are on average about 500 grams lighter than an equivalent disc brake bike. This is because forks and chainstays need to be reinforced. Disc brakes, shifters, and cabling themselves are also heavier.
While rim brakes are not as common, Elitewheels does offer premium and entry-level rim brake wheels. The Drive rim brake wheels start at only 1255 grams for the pair and feature ceramic bearings and carbon spokes. Marvel rim brake wheels are heavier, but are still very much performance wheelsets.
Do Different Types of Bike Require Different Brake Rotors?
Different types of bikes often require different types of disc brake rotors, which are tailored to suit the specific needs and conditions of various cycling disciplines.
Reduced Maintenance: pad replacement, adjustment and setup
Mountain Bikes
Mountain bikes commonly use larger rotors (160mm to 203mm) to provide greater stopping power and better heat dissipation, especially on steep descents and rough terrain. Rotors for mountain bikes are often made from high-quality stainless steel to withstand the harsh conditions and to provide durability and reliability.
Many mountain bike rotors have additional cooling features like vented or finned designs to enhance heat dissipation and prevent brake fade during long descents. Rotors designed for mountain biking often have larger cutouts or slots to help clear mud and debris, ensuring consistent braking performance in off-road conditions.
Elitewheels offers a number of mountain bike wheelsets that feature both Centerlock and 6-bolt brake options.
Road Bikes
Road bikes typically use smaller rotors (140mm to 160mm) as they generally don’t require as much stopping power as mountain bikes. The smaller size helps to reduce weight and aerodynamic drag. Lightweight rotors are preferred to keep the overall bike weight low, which is critical for road racing and endurance riding. Road bike rotors might have a simpler design with fewer cutouts compared to mountain bike rotors, focusing more on weight savings and aerodynamics. While heat dissipation is still important, the demands are generally lower than in mountain biking, so the designs might not be as aggressive in terms of cooling features.
Elitewheels offers a number of road wheelsets that feature both Centerlock and 6-bolt brake options.
Gravel and Cyclocross Bikes
Gravel and cyclocross bikes often use rotor sizes similar to road bikes, typically around 140mm to 160mm, balancing between adequate stopping power and weight. These rotors need to be robust enough to handle off-road conditions, including dirt, mud, and rough terrain. Similar to mountain bike rotors, gravel and cyclocross rotors might feature larger cutouts to help shed mud and debris. Rotors for these bikes are designed to perform well in a variety of conditions, from tarmac to gravel to muddy trails.
Elitewheels offers a number of gravel wheelsets that feature both Centerlock and 6-bolt brake options.
E-Bikes
E-bikes often use larger rotors just like mountain bikes (180mm to 203mm) to handle the increased weight and higher speeds associated with electric assistance. High-strength materials are used to ensure longevity and reliable performance under higher loads. Enhanced cooling features are critical to manage the increased heat generated by higher speeds and longer braking distances. E-bike rotors need to be particularly robust to cope with the increased forces and usage patterns.
Downhill Bikes
Downhill bikes use the largest rotors, typically 200mm to 220mm, to provide maximum stopping power and heat dissipation on extreme descents. These rotors are heavily vented and might include advanced cooling technologies such as finned rotors to manage the extreme heat generated during downhill runs. They are constructed to handle the high impact and extreme braking forces encountered in downhill racing.
BMX and Urban Bikes
BMX bikes usually have smaller rotors, around 140mm to 160mm, to maintain maneuverability and reduce weight. Simple and robust designs are preferred, as BMX bikes need to withstand the rigors of jumps and tricks. High durability is essential to handle the impact and stress from stunts and urban riding.
Commuter and Touring Bikes
Commuter and touring bikes typically use mid-sized rotors, around 160mm to 180mm, providing a balance of stopping power and weight. Durability is important, as these bikes are often used for long-distance riding and carrying loads. Designs focus on reliability and low maintenance, with good heat dissipation for long descents and heavy braking.
(Source: SJS CYCLES)
6-Bolt vs. Centerlock Rotors
6-Bolt Rotor
A 6-bolt rotor attaches to the hub using six bolts arranged in a circular pattern around the center of the rotor. These bolts secure the rotor firmly to the hub, ensuring that it rotates with the wheel. The 6-bolt rotor system is widely adopted across various types of bicycles, including mountain bikes, road bikes, and gravel bikes. It offers versatility and compatibility with a broad range of hubs and brake systems, allowing cyclists to choose from various rotor sizes and designs offered by different manufacturers. Installation and replacement of 6-bolt rotors are typically straightforward, requiring basic tools to tighten the bolts evenly.
Advantages
Widely Compatible: 6-bolt rotors are highly compatible with a broad range of hubs and brake systems, making them a versatile choice across different cycling disciplines and bike setups. This compatibility ensures that cyclists have numerous options for integrating 6-bolt rotors into their bikes without compatibility concerns.
Availability: They are widely available from numerous manufacturers and brands in various sizes and designs. Cyclists have ample choices for customization, whether they need specific rotor diameters or prefer particular rotor designs (such as vented or lightweight options).
Ease of Installation: Installing or replacing 6-bolt rotors is straightforward and typically requires basic tools, such as an Allen key or torque wrench, to secure the bolts evenly. This ease of installation simplifies maintenance tasks for cyclists who prefer to service their own bikes or make quick adjustments on the go.
Disadvantages
Alignment Issues: Achieving perfect alignment when installing 6-bolt rotors can sometimes be challenging, especially when changing rotors or wheelsets. Misalignment can lead to brake rub, where the brake pads make unwanted contact with the rotor, causing noise and potentially affecting braking performance. Careful adjustment and attention to rotor positioning are necessary to avoid these issues.
Weight: Compared to Centerlock rotor systems, the 6-bolt system tends to be slightly heavier. This additional weight is primarily due to the presence of six bolts and the corresponding rotor design. While the weight difference may be marginal, it can be a consideration for cyclists focused on minimizing overall bike weight, especially in competitive cycling.
(Source: SJS CYCLES)
Centerlock Rotor:
A Centerlock rotor system is an alternative disc brake rotor mounting standard that uses a splined interface to attach the rotor to the hub. Unlike the 6-bolt system, which uses individual bolts, Centerlock rotors feature a spline interface onto which the rotor slides onto the hub. A lockring secures the rotor in place, typically using a specific tool like a cassette lockring tool. Centerlock rotors are known for their easy and quick installation and removal process, requiring only one tool to secure or release the rotor. This system often results in weight savings compared to 6-bolt rotors due to the simplified interface design and fewer parts involved. While not as universally adopted as the 6-bolt standard, Centerlock rotors offer advantages in terms of convenience, especially for riders who frequently swap or service their disc brake rotors. They are commonly found on high-end mountain bikes, gravel bikes, and road bikes, providing a streamlined and efficient braking solution. Centerlock rotors are found with two types of lockrings:
External Lockring: This is the standard lockring used for most Centerlock rotors. It is a threaded ring that secures the rotor onto the splined interface of the hub. External lockrings often require a specific tool, such as a cassette lockring tool, for installation and removal.
Internal Lockring (XTR Standard): Shimano introduced a proprietary internal lockring design known as the XTR standard. This internal lockring is recessed within the hub interface and requires a different tool for installation and removal compared to the external lockring. It is designed to provide a cleaner look and potentially reduce weight, but it is less common and may not be compatible with all Centerlock hubs.
Advantages
Easy Installation: Centerlock rotors are renowned for their quick and straightforward installation process. They require only one tool—a lockring tool (often similar to a cassette lockring tool)—to securely mount or remove the rotor from the hub. This simplicity reduces installation time and can be advantageous for cyclists who frequently swap wheels or perform maintenance.
Weight Savings: Centerlock rotor systems often weigh less than their 6-bolt counterparts. The streamlined interface design and elimination of individual bolts contribute to these weight savings, making Centerlock rotors appealing for riders seeking to reduce rotational mass without sacrificing performance.
Cleaner Appearance: The Centerlock design offers a cleaner aesthetic compared to 6-bolt rotors. With fewer external bolts or protrusions on the rotor surface, the Centerlock system provides a sleeker, more integrated look. This aesthetic appeal can be desirable for cyclists who prioritize the visual aspects of their bike’s components.
Disadvantages
Less Common: While Centerlock rotors are gaining popularity, they are not as universally adopted as 6-bolt rotors. This may limit compatibility options depending on the hub and brake system setup chosen by cyclists. Availability of Centerlock-compatible hubs and rotor options can vary compared to the extensive availability of 6-bolt components.
Tool Dependency: Requiring a specific tool (lockring tool) for installation and removal can be a limitation if cyclists do not have access to this tool or prefer not to carry additional tools during rides or races. This tool dependency contrasts with the simpler tool requirements for installing 6-bolt rotors, which may influence some cyclists’ preferences.
Conclusion
Choosing between 6-bolt and Centerlock rotor systems involves weighing the advantages and disadvantages based on individual preferences, bike setup requirements, and intended use. 6-bolt rotors offer high compatibility, widespread availability, and straightforward installation, but they may require careful alignment and can be slightly heavier. In contrast, Centerlock rotors provide easy installation, potential weight savings, and a cleaner appearance, but they may offer fewer options and require a specific tool for installation and removal. Understanding these factors helps cyclists make informed decisions to best suit their cycling needs and preferences.
