Brake dynamics — consequence of locking the front wheels under braking If the front wheels of a vehicle lock during heavy braking, what is the most likely outcome?

Introduction / Context:
Wheel lock-up changes tyre forces and drastically affects directional control. Understanding the difference between front-wheel and rear-wheel lock-up is fundamental to safe braking and ABS benefits.

Given Data / Assumptions:

• Dry or low-μ surface without ABS assistance.
• Front wheels lock before rears (common in front-heavy cars without proper proportioning).
• Vehicle travelling straight before lock-up.

Concept / Approach:
When a tyre locks, it transitions from static to kinetic friction, losing lateral cornering capability. Locked front wheels cannot generate the lateral force required for steering, so the vehicle plows straight ahead (understeer to the extreme). Rear lock-up, in contrast, can induce a spin because the rear loses lateral stability first.

Step-by-Step Solution:
Front wheels lock → no lateral grip at the steered axle.Steering input has little effect because tyres are sliding.Vehicle maintains approximate heading and continues straight, reducing steering control.

Verification / Alternative check:
ABS systems are designed to prevent lock-up and preserve steerability by modulating brake pressure, illustrating how steer control is lost during lock-up.

Why Other Options Are Wrong:

• Very long stopping distance: not necessarily “extremely long”; the main issue is loss of steerability.
• Vehicle spins around due to front lock: spins are more associated with rear lock-up.
• Rear tyres skid: the premise states front-wheel lock, not rear.

Common Pitfalls:
Pumping brakes rapidly on ABS-equipped cars is counterproductive; maintain firm pressure and let ABS work.

Final Answer:
driver loses control over the steering, and the vehicle continues moving in its current direction