While we’ve talked quite a bit about braking in mountain biking (and literally wrote the book on it), the nuances of braking on road bikes have never been explored—until now.
MTB riders get it; braking is literally everything for riders who want to get faster on downhills (i.e. 90% of riders).
But road is different.
With so much emphasis on power meters and aero everything, riders have completely forgotten about the other side of road cycling - getting down the mountain with control and speed.
And it all comes down to how they use their brakes - something they are in complete control of.
Overbraking or braking in the wrong place is just wasted watts and lost speed. In fact, improper braking accounts for an insane amount of lost watts:
In the study discussed below, we found that braking cost a rider 63W on a 5-minute downhill!
Why Braking Matters in Road Cycling
Braking is important on the road for many reasons:
Safety: Effective braking can prevent accidents and ensure control during high-speed descents and sudden stops.
Performance: Optimizing braking techniques can lead to better speed conservation and improved overall performance.
Equipment Development: For manufacturers, precise braking data can inform the design of superior braking systems, enhancing the market appeal of their bikes.
The idea of measuring braking on road bikes started with some work we did with a big brand, and went from there.
After all these years of studying braking on MTB and watching results of good braking technique in the Tour de France, we wanted to dig in further.
To do this, we set up a “road bike” with our wireless BrakeAce PF2 brake sensors.
Key Findings from Brake Testing
Using the BrakeAce PF2 sensor, we conducted several tests to gather detailed insights into road bike braking. Here are some highlights:
Higher Torque Values: Road bike braking torque values when stopping exceed those measured while riding expert MTB trails.
Front vs. Rear Brake Use: The front brake on a road bike is used more compared to the rear brake. Most MTBers rely more on the rear brake than the front.
Braking Patterns: Road cycling involves relatively little braking during descending and city riding compared with MTB, but when riders are braking, they brake HARD.
Here are some specific insights from two out of our 6 scenarios:
Stopping Quickly from High Speed
Total Distance: 1.2 km
Max Speed: 49 kph
Max Force at Caliper: 1169 N
Max Brake Power (total): 3,287W
Max Rotor Surface Temperature (est.): 101℃ (front)
This scenario aimed to replicate a rider stopping from a high speed. Using just one brake was not feasible for safe stopping, necessitating the use of both brakes. The front brake showed a higher force, underscoring its critical role in high-speed stops.
This was one case where the idea of 70f/30r braking held true!
Short Steep Hill - Up and Back
Total Distance: 1.6 km
Max Speed: 55.4 kph
Max Force at Caliper: 452 N
Max Brake Power (total): 1,887W
Max Rotor Surface Temperature: 99℃ (front)
Navigating a steep hill required significant use of the front brake to manage speed effectively. This scenario highlighted the importance of front brake usage in maintaining control during rapid descents. Importantly however, we know that beginners are often not confident enough to use the front brake!
We did a number of other tests over that period, so reach out if you’re interested in the results.
Research Overview: Differences in Braking Demand
To expand on the science, we wanted to compare braking on the road directly to braking on the MTB by matching a descent for elevation loss. Here’s a summary of our research findings (read the full SESNZ conference book of abstracts here):
Summary of Research Paper Abstract
In our study, we compared braking during a road cycling descent (DHR) and a mountain biking descent (DHM) using the BrakeAce PF2 wireless brake sensors. Both descents had similar elevation loss, but the braking dynamics varied greatly:
Average Speed: Higher on the road (DHR) at 11.0 m/s compared to 4.5 m/s on the MTB trail (DHM).
Brake Time: Similar total brake time, but the brake work and power were much higher in road cycling.
Brake Events: Road cycling showed a greater reliance on the front brake (62/38%) compared to MTB (30/70%).
Brake Power: Significantly higher average brake power on the road (805W) versus MTB (362W).
Brake Work: Higher total brake work on the road (19.1 kJ) compared to MTB (9.2 kJ).
You can extrapolate out these results for yourself - this is where the lost 63W were calculated from!
By the way, to put this 63W loss into context, the same rider would need to add almost 22kg to their bike to lose the same amount of watts on the climb - this is how important braking is!
(Assuming 70kg rider at 200W on a 3.3km, 228m road climb)
Engineering Challenges in Road Bike Braking
It’s important that manufacturers take these results into account when building bikes or components. There is a general consensus that braking is much more demanding on the MTB (and it IS incredibly demanding), but we’re seeing incredibly high brake torque on the road bike.
One reason for the increased braking forces on the road is that braking comes with huge changes in speed.
Here are some important notes about braking on the road:
High-Speed Braking: Road bikes achieve higher speeds, requiring brakes that can handle greater forces and provide reliable stopping power without compromising stability. Think about the bikes themselves and how they respond to braking, plus the componentry.
Heat Dissipation: High-speed braking generates significant heat. Effective heat dissipation mechanisms are crucial to prevent brake fade and ensure consistent performance. With tiny road bike brake rotors and calipers, there isn’t much mass for heat storage.
Save Watts on the Road
There is huge potential to integrate brake sensors into road cycling. Analyzing braking data and braking patterns can not only help riders improve their safety, but adding brake sensors to a suite of power meters and aero sensors can help riders find massive gains - forget marginal gains!
Here are a few ways roadies can achieve huge gains:
Power Meters: Combining braking data with power meter readings can help cyclists understand the impact of braking on overall power output and efficiency. If you put in a big effort and brake it all away into the next corner, you can focus on burning your matches when it counts.
Aero Sensors: Integrating braking data with aerodynamic measurements can provide insights into how braking compares to improvements in aerodynamic drag. If you're going faster thanks to better aerodynamics, are you just braking all those gains away?
Performance Optimization: Detailed braking data allows for fine-tuning of braking techniques and equipment, leading to better speed conservation and improved overall performance.
Improved Technique: Many riders shy away from the front brake, which has devastating effects when it comes time to stop in a hurry - they simply can’t stop without the front brake.
Conclusion
Braking on road bikes is more complex and impactful than many riders realize. By leveraging tech like BrakeAce, we can gain invaluable insights into braking patterns, optimize performance, and improve safety.
Integrating this data with power meters and aero sensors will help you find those marginal gains that make all the difference in performance. So next time you're focusing on climbing power and aerodynamics, remember: effective braking is just as crucial to your success on the road.
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