Automobile & Light Truck Certification Test A5 BrakesDisc Brake Diagnosis and RepairEasy
A technician is performing a pre-purchase inspection on a used vehicle. They observe significant grooving and scoring on the front brake rotors, along with a noticeable lip on the outer edge. Which of the following is the MOST appropriate recommendation?
- ARe-surface the rotors and re-install the original brake pads.
- BReplace only the brake pads, as the rotors can be re-surfaced.
- CReplace both the brake pads and rotors.
- DBleed the brake system, as air in the lines can cause rotor damage.
Show answer & explanationAnswer & explanation
Correct answer: C. Replace both the brake pads and rotors.
Significant grooving, scoring, and an outer lip indicate that the rotors are likely beyond their service limit or are severely damaged. In such cases, both the pads and rotors should be replaced to ensure optimal braking performance and safety.
Why the other options are wrong
- A. Re-surfacing might not be possible, and re-installing old pads on new or re-surfaced rotors can lead to noise and accelerated wear.
- B. Re-surfacing severely grooved rotors may thin them beyond the minimum thickness, compromising safety and performance.
- D. Air in the brake lines affects pedal feel and braking efficiency but does not directly cause physical damage like grooving or scoring to rotors.
Rotor Replacement Indicators
Key signs that brake rotors need replacement rather than just re-surfacing or reuse.
- Excessive grooving or scoring.
- Warping (pulsation during braking).
- Cracks or heat spots.
- Reaching or exceeding minimum thickness specification.
Memory trick: Grooves and lips mean it's time for new trips.