Brake fluid characteristics |Total Lubricants

Brake fluid characteristics

Main characteristics-

Low compressibility

Low compressibility

Constant boiling point

Constant boiling point

Low freezing

Low freezing point

Lubrication of moving parts

Lubrication of moving parts

Materials compatibility

Materials compatibility

Anticorrosion protection

Anticorrosion protection

Oxidative resistance and thermal stability

Oxidative resistance and Thermal stability

Brake fluids must maintain low level of compressibility which remains low even when temperatures and pressure vary.

Water/moisture can be found in almost all brake systems. Moisture enters into the brake system in several ways.
For example condensation can form in lines and calipers. As caliper and line temperatures heat up and then cool repeatedly, condensation occurs, leaving behind an increase in moisture/water. Over time the moisture becomes trapped in the internal sections of calipers and lines master cylinders.

For reliable, consistent brake system operation, brake fluid must maintain a constant viscosity under a wide range of temperatures, including extreme cold.

This is especially important in systems with an anti-lock braking system (ABS), traction control, and stability control.

Both master and slave cylinders of drum and disc brake systems contain pistons which must be able to move freely.

To reduce friction and wear, polygycols are added to break fluids as lubricants.

Brake fluids must be compatible with brake system materials.

Seals swelling tests are carried out at 70°C and 120°C on standardized SBR and EPDM rubber specimens and on specific elastomers used by OEMs.

During these tests changes in the volume, diameter and hardness of the specimens are measured.

Additives (corrosion inhibitors) are added to the base fluid to protect metal used inside components such as calipers, master cylinders… against corrosion

Braking is the conversion of kinetic energy into heat by friction. The quantities of heat that result are considerable and depend on the weight and speed of the vehicle.

Nevertheless, under extreme conditions of operation, brake fluids reach temperatures of more than 150°C. Their cracking phenomenon is a direct measure of their thermal stability. This is determined by the quality of glycol ethers components and the quantity and nature of antioxidants.

Antioxidants improve the thermal stability and also hold up the aging of the fluid by oxidation into acidic components.

 

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