What is "brake lock-up"?

Brake lock-up refers to a situation where the wheels of a vehicle stop rotating while the brakes are applied, which can result in a loss of traction. This occurs because when the brakes are applied too forcefully, the friction created between the brake pads and rotors can exceed the available traction between the tires and the road surface. The wheels then skid, reducing the driver's ability to maintain control over the vehicle.

This phenomenon is particularly relevant in situations involving sudden braking or on slippery surfaces where the grip is limited. Locking up can lead to longer stopping distances and can cause the vehicle to skid out of control, making it difficult to maneuver. For this reason, many modern vehicles are equipped with Anti-lock Brake Systems (ABS) that help prevent wheel lock-up and maintain traction during hard braking.

The other choices do not accurately describe the concept of brake lock-up. Non-functioning brakes or brake fluid leaks pertain to complete brake failure or issues leading to inadequate braking, while worn brake pads are related to decreased braking efficiency rather than the immediate effects of lock-up during braking.