Brake fluid

Brake Fluid

Brake fluid is a type of hydraulic fluid used in hydraulic brake and hydraulic clutch applications in automobiles, motorcycles, light trucks, and some bicycles. It is used to transfer force into pressure, and to amplify braking force. Since braking involves converting a vehicle's kinetic energy into heat, brake fluid must have a high boiling point to avoid vaporizing within the brake lines.

Properties

Brake fluid is subjected to very high temperatures, especially in the wheel cylinders of drum brakes and disc brakes. It must have a high boiling point to avoid vaporization, which can lead to brake failure. There are several important properties that brake fluid must possess:

• Boiling Point: Brake fluids are classified by their boiling points, which are measured in both "dry" and "wet" conditions. The "dry" boiling point is the temperature at which the fluid will boil when it is new and contains no water. The "wet" boiling point is the temperature at which the fluid will boil after it has absorbed a certain amount of moisture.

• Viscosity: Brake fluid must maintain a consistent viscosity over a wide range of temperatures to ensure that it flows properly through the brake system.

• Corrosion Resistance: Brake fluid must not corrode the metal components of the brake system.

• Compatibility: It must be compatible with the rubber seals and hoses used in the brake system.

Types of Brake Fluid

There are several types of brake fluid, classified by their chemical composition and performance characteristics:

• DOT 3: Glycol-based fluid with a minimum dry boiling point of 205°C (401°F) and a wet boiling point of 140°C (284°F).

• DOT 4: Glycol-based fluid with a higher boiling point than DOT 3, with a minimum dry boiling point of 230°C (446°F) and a wet boiling point of 155°C (311°F).

• DOT 5: Silicone-based fluid that does not absorb water, with a minimum dry boiling point of 260°C (500°F) and a wet boiling point of 180°C (356°F). It is not compatible with DOT 3 or DOT 4 fluids.

• DOT 5.1: Glycol-based fluid with a boiling point similar to DOT 5, but it is compatible with DOT 3 and DOT 4 fluids.

Maintenance

Brake fluid is hygroscopic, meaning it absorbs moisture from the air over time. This can lower its boiling point and lead to brake failure. Therefore, it is important to regularly check and replace brake fluid according to the vehicle manufacturer's recommendations.

Safety

Brake fluid is toxic and can be harmful if ingested or if it comes into contact with skin. It is also flammable, so it should be handled with care. Used brake fluid should be disposed of properly to avoid environmental contamination.

Also see

• Hydraulic brake
• Disc brake
• Drum brake
• Clutch
• Automobile safety