Clip-On Aero Bars: Performance Gains, Ergonomics, and Safety Considerations

How much difference do clip on Aero bars make?

Clip-on aero bars can make a significant difference in cycling performance, primarily by improving aerodynamic efficiency and reducing drag, which can translate into substantial time savings and power conservation, especially at higher speeds and over longer distances.

What Are Clip-On Aero Bars?

Clip-on aero bars, also known as aerobars, time trial bars, or tri-bars, are handlebar extensions designed to allow a cyclist to adopt a more aerodynamic, forward-leaning position. They typically consist of two forward-extending bars with armrests, which clip onto a standard road bike handlebar. This setup enables the rider to support their upper body on their forearms, bringing their torso into a flatter, more streamlined profile, and often narrowing their shoulder width.

The Science of Aerodynamics in Cycling

The primary resistance a cyclist faces, particularly at speeds above 15-20 mph (24-32 km/h), is aerodynamic drag. This force increases exponentially with speed; doubling your speed quadruples the air resistance. Aerodynamic drag is primarily determined by two factors:

• Frontal Area: The cross-sectional area of the rider and bike pushing through the air.
• Drag Coefficient (Cd): A measure of how "slippery" the shape is.

Aero bars work by significantly reducing the rider's frontal area and improving their drag coefficient. By allowing the rider to tuck their head, flatten their back, and bring their arms closer together, the overall profile presented to the wind becomes smaller and more streamlined, cutting through the air more efficiently.

Quantifying the Difference: Performance Gains

The performance gains from using clip-on aero bars can be substantial, though they vary based on several factors:

• Wattage Savings: Studies and real-world data suggest that adopting an aggressive aero position can save a cyclist between 15 to 30 watts at moderate to high speeds (e.g., 20-25 mph or 32-40 km/h). This is a significant amount of power that can either be used to go faster or to maintain the same speed with less effort.
• Time Savings: These wattage savings directly translate into time savings over a given distance.
  • For a 40 km (25 mile) time trial, a well-executed aero position can save 2 to 5 minutes compared to riding on standard drop handlebars, depending on the rider's speed and initial position.
  • Over longer distances, such as an Ironman triathlon (180 km or 112 miles), these savings can accumulate to 15-30 minutes or more.
• Speed Increase: For a given power output, aero bars can increase average speed by 1-2 mph (1.6-3.2 km/h) or more, especially when riding solo on flat to rolling terrain.

Factors Influencing Performance Gains

The actual difference clip-on aero bars make is not universal and depends on:

• Rider Speed: The faster you go, the more significant the impact of aerodynamic drag, and thus the greater the benefit from aero bars. At slower speeds (e.g., casual touring), the benefits are minimal.
• Rider's Initial Position: A rider who already has a very aggressive, low position on standard drops will see less relative gain than someone who rides very upright.
• Ability to Hold the Position: The aero position requires core strength, flexibility, and comfort. If a rider cannot comfortably sustain the position for extended periods, the gains may be negated by reduced power output or discomfort.
• Course Profile: Aero bars are most effective on flat to rolling terrain. On very hilly courses or technical routes with frequent braking and cornering, their utility decreases.
• Wind Conditions: Headwinds amplify the benefits of aerodynamics. Crosswinds can make holding the aero position more challenging due to increased instability.

Ergonomics and Comfort Considerations

While speed is a primary driver, ergonomics and comfort are critical for maximizing the benefits of aero bars:

• Sustained Power Output: An overly aggressive or uncomfortable aero position can restrict breathing, cause neck or back pain, or put undue pressure on sensitive areas, leading to a drop in power output. A slightly less aerodynamic but more comfortable position that allows for sustained power is often faster overall.
• Core Strength and Flexibility: Holding the aero position requires good core strength to support the upper body and flexibility in the hamstrings, glutes, and lower back to maintain a flat back.
• Armrest and Extension Adjustability: Quality clip-on aero bars offer significant adjustability for armrest width, stack height, and extension length and angle, allowing for a personalized fit.

Potential Drawbacks and Safety

Despite the performance advantages, there are considerations and potential drawbacks:

• Handling and Stability: Riding in the aero position narrows the rider's grip and shifts weight distribution, making the bike less stable and more challenging to handle, especially at low speeds, over rough terrain, or in strong crosswinds.
• Braking and Shifting Access: In the aero position, brake levers and gear shifters are not immediately accessible. This requires the rider to move their hands to the base bar, which can be critical in situations requiring quick reactions.
• Safety in Group Riding: Due to reduced handling control and delayed braking, riding in the aero position is generally discouraged and often prohibited in group rides and most mass-start road races. They are primarily for solo efforts, time trials, and triathlons.
• Weight Penalty: While typically minimal, clip-on aero bars add a small amount of weight to the bike.

Who Benefits Most?

Clip-on aero bars are most beneficial for:

• Time Trialists: Where every second counts, and the entire race is a solo effort against the clock.
• Triathletes: Especially for the bike leg of long-distance triathlons, where sustained speed and energy conservation are crucial.
• Long-Distance Road Cyclists: For solo training rides or unsupported endurance events where maintaining a high average speed is important.
• Commuters (on specific routes): For long, uninterrupted stretches of road where speed and efficiency are desired, assuming safety is not compromised.

Proper Setup and Fit

To maximize the benefits and ensure safety, proper setup and fit of clip-on aero bars are paramount. This often requires:

• Professional Bike Fit: A qualified bike fitter can help determine the optimal position, balancing aerodynamics, comfort, power output, and handling. This includes adjusting saddle position, armrest placement (width, stack, reach), and extension angle.
• Practice: Becoming comfortable and proficient in the aero position takes practice. Start with short durations on quiet roads before attempting longer rides or higher speeds.
• Core Engagement: Focus on engaging your core to support your upper body rather than relying solely on your arms and neck, which can lead to fatigue and discomfort.

Conclusion

Clip-on aero bars can make a profound difference in cycling performance, primarily through significant aerodynamic gains that translate into substantial wattage and time savings. For cyclists engaged in time trials, triathlons, or long-distance solo efforts, they are an invaluable tool for efficiency and speed. However, these benefits are contingent upon a proper fit, the rider's ability to comfortably sustain the position, and an understanding of the associated handling and safety considerations. When used appropriately, aero bars are a testament to how intelligent application of exercise science and biomechanics can dramatically enhance athletic performance.