Signs of bad car rotors include brake noise, a vibration or wobbling when pressing the brakes, or squealing or squeaking noises. Grinding noises when pushing the brake pedal also indicate bad rotors. Anti-lock braking systems contain sensors that warn drivers when their brakes are too low.
Drivers can also check rotors by looking through the tires to check for ridges that form on the rotors. A tool called a micrometer determines the thickness of the ridges, and if the ridges are not too deep, mechanics can smooth the rotors, which removes the ridges.
Burning or pungent smells at or near the tires are another sign that brake rotors or brake pads need servicing. Drivers who smell any type of unfamiliar odor around their tires must seek out the services of professional mechanics immediately. Other signs that brake rotors or brake pads need replacement or service include needing to press down harder on the brakes to complete stops, observing brake warning light indicators, low brake fluid levels or air leaks from brake lines. To help rotors last longer, drivers should reduce stop-and-go driving as much as possible and avoid riding their brakes. Aggressive driving habits also lead to wear and tear on rotors and brake pads.