Michigan State Brakes Certification Practice Exam

A car's wheels severely vibrate when the brakes are applied. Which of the following is the LEAST likely source of the problem?

1. The brake pads

2. A warped brake rotor

3. A malfunctioning wheel hub

4. The master cylinder

The correct answer is: The master cylinder

Vibration in a car's wheels when the brakes are applied is most commonly associated with issues directly related to the braking system, particularly components that come into direct contact with the rotors and pads. The master cylinder's primary function is to generate hydraulic pressure and send brake fluid to the brakes, but it does not share direct physical interaction with the wheels when brakes are applied. If the master cylinder were malfunctioning, one would typically expect issues like a spongy brake pedal, loss of braking power, or brake fluid leaks rather than vibrations from the wheels. In contrast, problems such as warped brake rotors can cause significant vibrations since they affect how the brake pads engage with the braking surface. Similarly, the condition of the brake pads directly impacts friction during braking, and any inconsistencies can lead to uneven contact, resulting in vibrations. A malfunctioning wheel hub may also cause vibrations due to its role in supporting the wheel assembly. Overall, while all components are essential to the vehicle's braking system, the master cylinder's indirect role makes it the least likely source of severe wheel vibrations under braking conditions.