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Brake Fade

“When Brake Fluid moisture content is low boiling point is High”
IDEAL CONDITION

Brake fade is can occur when braking heavily for an extended period, especially when driving downhill.

In most cases the cause is too high a moisture content in the brake fluid.

Brake fluid is hydroscopic, in other words is absorbs water. As the moisture content in the brake fluid increases so too does the boiling point of the contaminated brake fluid decrease. As the fluid boils it gives off air bubbles.

“As Brake Fluid moisture content increases increases the boiling point of the the brake fluid decreases”
This is BAD!

In a sealed hydraulic system with no air in the system pressure applied to the brake pedal is transferred to the caliper pistons to the brake pads. As pressure is applied to the brake pedal the fluid, pressure is increased throughout the entire system. Fluids do not lose volume when compressed. Air does.

With air in the hydraulic braking system the overheating causes loss of effectiveness, resulting in a reduction in stopping power.

To reiterate during extended downhill driving, the brake system becomes subjected to higher frictional forces compared to level driving. The increased friction generates higher temperatures in the brake pads, rotors and other components in the brake system. As excessive temperatures build up, the brake fluid boils, causing a loss in pressure, this reduces the system’s ability to transfer hydraulic force from the brake pedal to the wheels.

“The air bubbles take the place of the brake fluid in the brake cylinder this causes brake fade.”
This Is Dangerous!

If you experience brake fade while driving downhill, you should stop for a while to let the brake system to cool down. You should seek professional advice a soon as possible. If you have to continue your downhill travel you should make use of engine braking by shifting to a lower gear to maintain slower speeds. Using the gearbox helps transfer some braking effort to the engine, thus reducing the amount of heat buildup.

Holding the brake pedal down continuously will quickly raise the temperate of the fluid and the fade will return

Another strategy is to consider using lower gears when going downhill, which reduces the speed and the load on the brake system, thus reducing heat buildup. This can be significantly helpful when towing, running heavy loads or when driving in mountainous terrains.

If you experience brake fade in, you should avoid driving at high speeds, especially when carrying heavy loads or towing.