Understanding Brake Fluid

Brake fluid is an incompressible liquid that acts on the disc brake piston. It consists of polyhydric alcohols and esters that have a high boiling point, maintaining its properties over a long period.

However, there are many types of fluids, the most common being Dot 4 glycol-based, which is fitted in most production cars. Dot 5, which is silicone-based, is also used.

These two fluids must NEVER be mixed, as they are not compatible. If this happens, you must bleed and flush the system.

Then, check if the system is compatible with that type of fluid. If you have a system designed for Dot 4, it is very risky to use another type of Dot, which could damage seals and components.

An important aspect of brake fluid is the boiling point: the "dry boiling point" is the minimum temperature at which the brake fluid will not produce air bubbles. In this case, braking may become prolonged due to air bubbles.

The "wet boiling point" is the boiling point when the fluid absorbs moisture, which lowers the boiling point over time, typically after 1 or 2 years. The maximum allowable water content in the fluid is 7.5%; beyond this percentage, the fluid would completely lose its properties.

Therefore, check the level in the reservoir every 2 to 3 months, replace all the fluid in the system every 24 months, and always wear gloves when handling it, as it is very harmful to eyes and skin, as well as to the bodywork. So, take great care.

Also, clean the brake pads thoroughly, as they can also be very damaging.