Water incursion can be a concern even in well-sealed and properly installed disc brake systems. It’s important to note that even a small amount of moisture introduced into the brake system can lower the brake fluid’s boiling point.
Water has a lower boiling point compared to the temperatures experienced at the caliper during heavy braking. The boiling point of a brake fluid that contains water is referred to as the ‘wet boiling point’ and is a critical parameter because it indicates the point at which the brake fluid can start to boil when water is present.
Boiling within the brake fluid leads to the formation of vapor or gas bubbles. These bubbles are compressible and can be easily compressed by the rider when squeezing the brake lever. As a result, the brake lever may feel spongy, and the brake’s effectiveness is significantly reduced.
Minimizing the risk of water contamination is crucial to maintaining brake performance.
While modern brake systems are designed to be highly sealed and resistant to external contaminants, water incursion can still occur due to several factors:
Condensation: Over time, temperature variations and changes in riding conditions can lead to condensation inside the brake system. As the temperature fluctuates, moisture-laden air can be drawn into the system when the brake cools down after a ride. This condensation can introduce small amounts of moisture into the brake fluid.
Improper Bleeding: During routine brake maintenance or when servicing the brake system, improper bleeding procedures can introduce air and moisture into the system. If bleeding is not performed correctly, it can compromise the integrity of the brake fluid.
Water at the Interface: In certain riding conditions, such as riding in heavy rain or through water crossings, water can splash onto the caliper, rotor, or hose connections. If the seals or connections are not perfectly secure, they may allow water to penetrate the system.
Hygroscopic Nature of Rubber Seals: While brake systems are designed with rubber seals to keep contaminants out, rubber can still absorb moisture from the environment over time. This is why regular maintenance and seal inspection are essential.
Crash or Impact Damage: In the event of a crash or impact, the integrity of the brake system may be compromised. Damaged hoses, seals, or connections can allow water to enter the system.
To mitigate the impact of water incursion and maintain optimal brake performance, regular brake fluid replacement and maintenance are recommended. This helps ensure that the fluid remains closer to its dry boiling point, providing a safety margin during heavy braking scenarios. It is essential for high-performance cyclists to adhere to manufacturer-recommended brake fluid replacement intervals and monitor the condition of the brake fluid to guarantee a reliable and responsive braking system.