Yes, many professional cyclists use disc brakes on their bikes, especially in road racing and other cycling disciplines. Disc brakes offer several advantages over traditional rim brakes:

1. Improved braking performance: Disc brakes generally provide more consistent and powerful braking performance, especially in wet or adverse weather conditions. This can be crucial in professional racing scenarios where split-second braking decisions are important.
2. Heat dissipation: Disc brakes are better at dissipating heat compared to rim brakes, which can be important when descending long and steep mountain passes. This helps prevent brake fade and maintains consistent braking performance.
3. Less rim wear: Rim brakes can cause wear and tear on the rims of the wheels, which can be an issue in high-intensity racing. Disc brakes don’t wear down the rim surface, potentially extending the life of the wheel.
4. Wider tire compatibility: Disc brakes allow for wider tire clearance, which can improve traction, comfort, and overall performance, especially on varied road surfaces.
5. Aero advantages: Some disc brake systems are designed to be more aerodynamic than traditional rim brakes, which can be advantageous in races where aerodynamics play a significant role.
6. Modulation and control: Disc brakes offer better modulation and control over braking force, allowing cyclists to apply just the right amount of braking power.

However, the adoption of disc brakes in professional cycling hasn’t been without controversy. In the past, there were concerns about safety issues, such as the potential for sharper disc rotors causing injuries in crashes or pile-ups. Nevertheless, advancements in design and safety measures have largely addressed these concerns.

As of my last knowledge update in September 2021, disc brakes were becoming increasingly common in professional cycling, but the exact prevalence might have changed since then. It’s advisable to consult recent sources for the most up-to-date information on the use of disc brakes in professional cycling.

As of my last knowledge update in September 2021, not all professional cyclists were using disc brakes. The adoption of disc brakes in the professional cycling peloton varied depending on the team, race, and individual rider preferences. While many professional cyclists had made the switch to disc brakes for the reasons mentioned earlier, there were still some who preferred traditional rim brakes for various reasons.

Factors influencing the decision to use disc brakes or not include:

1. Team and Sponsorship: Some professional cycling teams and their sponsors might have specific preferences or contracts related to the type of brakes used by their riders.
2. Race Conditions: The type of race and the specific conditions it presents can influence brake choice. For example, in mountainous stages, disc brakes might offer significant advantages for descending, while in flatter stages, the benefits might be less pronounced.
3. Rider Preference: Cyclists might have personal preferences for braking feel, modulation, and the overall riding experience that could sway their choice.
4. Regulations: At the time of my last update, cycling’s governing body, the Union Cycliste Internationale (UCI), had approved the use of disc brakes in professional racing. However, there might have been specific rules or regulations related to their use in different races or events.
5. Availability of Equipment: Availability of suitable bikes and components equipped with disc brakes could also play a role in whether a rider uses them.
6. Transition Period: The adoption of new technology like disc brakes can take time to fully integrate into the peloton. Some riders might still be in a transitional phase while they adapt to the new technology.

It’s important to note that the situation might have evolved since September 2021. To get the most accurate and up-to-date information on the use of disc brakes in professional cycling, I recommend checking cycling news sources, team announcements, and official race reports.

Disc brakes generally have the potential to offer better and more consistent stopping power compared to traditional rim brakes, especially in adverse conditions like wet or muddy roads. However, it’s important to note that the actual stopping distance can be influenced by a variety of factors beyond just the type of brakes, including the quality of the brake components, the condition of the road surface, the rider’s technique, and the overall bike setup.

Here are a few reasons why disc brakes might offer better stopping power:

1. Consistent Performance: Disc brakes are less affected by external factors like water, mud, and debris on the road surface. This consistency can result in more reliable and powerful braking even in unfavorable conditions.
2. Leverage: The design of disc brakes allows for greater mechanical advantage, which can translate to stronger and more controlled braking.
3. Heat Dissipation: Disc brakes are generally better at dissipating heat, which is important in preventing brake fade during prolonged or intense braking. This can be particularly relevant in scenarios like long descents.
4. Modulation: Disc brakes often provide better modulation, allowing the rider to apply the brakes more gradually and precisely. This can be important in maintaining control, especially on challenging terrain.
5. Wheel Design: With disc brakes, the braking force is applied at the hub of the wheel, rather than on the rim. This can reduce the risk of overheating the rim, which might occur with rim brakes during prolonged or heavy braking.
6. Tire Clearance: Disc brakes allow for wider tire clearance, which can result in improved traction and contact with the road, potentially aiding in quicker stopping.

However, it’s essential to emphasize that while disc brakes can offer advantages, proper setup, maintenance, and technique are crucial for achieving optimal braking performance. Additionally, the difference in stopping power might not always be significant in every real-world scenario. Cyclists need to adapt their braking technique to the specific characteristics of their chosen braking system.

As technology and engineering continue to advance, the performance gap between disc brakes and rim brakes might continue to narrow, and the choice between the two will also depend on personal preference, riding style, and the specific demands of the cycling discipline.

The lifespan of disc brakes can vary widely depending on several factors, including the quality of the components, the riding conditions, maintenance practices, and the rider’s braking habits. Here are some considerations that can affect the lifespan of disc brakes:

1. Quality of Components: Higher-quality disc brake components, including rotors, brake pads, and calipers, generally have a longer lifespan. Premium components might resist wear, heat, and corrosion better than cheaper alternatives.
2. Riding Conditions: Riding in wet, muddy, or abrasive conditions can accelerate wear on disc brake components. In such conditions, brake pads and rotors may wear out more quickly.
3. Maintenance: Regular maintenance can significantly extend the lifespan of disc brakes. Keeping the braking system clean, adjusting calipers and brake pads properly, and ensuring the rotors are free from contaminants can all contribute to longevity.
4. Braking Habits: Aggressive braking, particularly prolonged heavy braking or dragging the brakes on descents, can generate more heat and wear on the components. Smooth and controlled braking can help extend the lifespan.
5. Type of Riding: Different types of riding put different levels of stress on the braking system. For example, downhill mountain biking places more demands on disc brakes than casual road cycling.
6. Rotor and Pad Material: The type of rotor and brake pad material can affect wear rates. Some rotor materials might wear faster than others, and the composition of brake pads can influence how quickly they wear down.
7. Riding Frequency: The more frequently you ride, the more wear and tear your disc brakes will experience over time.

As a rough estimate, well-maintained disc brake pads might last around 1,000 to 4,000 miles (1600 to 6400 kilometers) of riding. Rotors can last longer, often between 2,000 to 6,000 miles (3200 to 9600 kilometers) or even more, depending on the factors mentioned above.

It’s important to monitor your brake components regularly for signs of wear, such as reduced braking performance, noise, or visible thinning of brake pads. If you’re unsure about the condition of your disc brakes, it’s a good idea to have them inspected by a professional bike mechanic, who can provide personalized advice based on your specific riding habits and conditions.