Michigan State Brakes Certification Practice Exam

What is a common cause of vibration or pulsation in the brakes when applied on disc-drum systems?

1. Worn brake pads

2. Rotor thickness variation

3. Improper brake fluid

4. Faulty brake lines

The correct answer is: Rotor thickness variation

The presence of vibration or pulsation in the brakes when applied in disc-drum systems can be commonly attributed to rotor thickness variation. This condition occurs when the rotors have uneven thickness due to wear, warping, or improper machining. When the brake pads come into contact with a rotor that has inconsistent thickness, it creates fluctuating resistance which translates to a pulsating sensation in the brake pedal or steering wheel. This is because the brake calipers are applying force inconsistently as they encounter varying thickness levels throughout the rotor's rotation, leading to ineffective braking and a compromised driving experience. Other factors such as worn brake pads, improper brake fluid, or faulty brake lines might contribute to braking issues but are less directly related to the specific symptom of vibrations or pulsations. Worn brake pads could cause noise or reduced effectiveness, while brake fluid quality typically influences pedal feel and may result in brake failure if contaminated. Faulty brake lines primarily affect hydraulic performance rather than directly causing a pulsating sensation during braking.