Brake Systems Flashcards

What is the purpose of the brake wear indicator (squeal tab)?

Answer: To produce an audible warning sound when the brake pad friction material has worn to the replacement point

The brake wear indicator is a small metal tab attached to the brake pad that contacts the rotor when the pad reaches minimum thickness, producing a high-pitched squeal to alert the driver that pad replacement is needed.

What is the purpose of cross-drilled or slotted brake rotors?

Answer: To improve heat dissipation, allow gas and water escape from the pad-rotor interface, and maintain consistent friction

Cross-drilled holes and slots help dissipate heat, allow water, gas, and debris to escape from between the pad and rotor surface, and provide a fresh edge for the pad to bite, maintaining consistent braking performance.

What is the function of the hill descent control (HDC) system?

Answer: To automatically apply the brakes to maintain a slow, controlled speed during steep downhill driving without driver pedal input

HDC uses the ABS/ESC system to automatically pulse the brakes on steep descents, maintaining a preset slow speed (typically 5-25 km/h) without the driver needing to use the brake pedal, preventing runaway on steep grades.

What is the effect of moisture contamination in DOT 3 or DOT 4 brake fluid?

Answer: The boiling point is significantly lowered, increasing the risk of vapour lock during heavy braking

DOT 3 and DOT 4 are hygroscopic — they absorb moisture from the atmosphere over time. Water lowers the fluid's boiling point dramatically (the 'wet' boiling point), increasing the risk of vapour lock and brake fade.

What is the purpose of the emergency brake assist (BA) system?

Answer: To detect a panic braking situation and automatically apply maximum braking force faster than the driver can

Brake assist monitors the speed and force of brake pedal application. If it detects a panic stop (fast pedal application), it immediately applies full braking force, reducing stopping distance for drivers who may not press hard enough.

A brake rotor has blue discolouration on the friction surface. What does this indicate?

Answer: The rotor has been overheated, potentially causing metallurgical changes that reduce braking effectiveness and promote cracking

Blue discolouration (heat spots) indicates the rotor has been subjected to extreme temperatures, causing metallurgical changes in the cast iron. These areas become hardened (hard spots), reduce friction, and are prone to cracking. The rotor should be replaced.