What are brake rotors?
A brake rotor is a metal disc, attached to a vehicle’s wheel hub, that receives friction from the brake pads to stop the vehicle. The rotor is situated within a caliper, which houses brake pads situated on either side of the rotor. When you press your brake pedal, hydraulic pressure from the brake fluid pushes a piston(s) causing the brake pads to squeeze the rotor and bring your wheels to a stop. Brakes consisting of a rotor, brake pads, and calipers are called disc brakes.
The other common brake type is the drum brake. These have shoes instead of pads, and drums instead of rotors. Most new cars today have either disc brakes on all four wheels or disc brakes on the front wheels and drum brakes on the rear wheels.
Brake rotors wear down over time due to contact with brake pads. But you don’t necessarily need new rotors with each brake pad replacement. Most rotors can be resurfaced one or more times to extend their life. But each resurfacing makes the rotors thinner, and sooner or later you’ll need new ones. Always follow the recommendations of the vehicle manufacturer when replacing rotors.
How can I tell if I need new brake rotors?
Here are some signs that it’s time to inspect your brake rotors for possible resurfacing or replacement:
- A high-pitched screeching sound from your brakes - That’s the dreaded “metal on metal” sound telling you that your brake pads are worn down completely. Your metal calipers are probably digging deep grooves into your rotors.
- Squeaky brakes - Brake pad material has transferred to the rotor.
- Vibrations or jittery sensation when braking - Your brake rotors might be warped.
Before that point, your mechanic can tell you when your rotors are too worn from brake pad contact to be safely resurfaced. Mechanics are required to replace any rotor that’s worn to a level below its manufacturer-required minimum thickness.
The most convenient time to check the rotors is during a Brake Inspection. On most vehicles, it’s difficult to get a good look at your brake rotors yourself without removing the wheels. Your Midas technician will advise you if it’s time for new rotors now or whether it’s a job that can wait.
What causes grooves in brake rotors?
Brake rotors are expected to wear down in the shape of brake pads, and these indentations can often be resurfaced away (until the rotor gets too thin and must be replaced). Grooves can also be caused by foreign objects under the brake pads, corrosion, or by softer metal in the rotors than on the brake pads. These, too, can be resurfaced as long as the groove isn’t deeper than the rotor’s minimum thickness.
What causes brake rotors to warp?
The most common cause of brake rotor warping is excessive heat buildup caused by:
- Glazing from brake pad material - Pieces of brake pad material can transfer onto the rotor.
- Rotors that are too thin to dissipate heat - Rotors wear thin due to regular use (and resurfacing during brake service). When they’re below the manufacturer’s minimum thickness, it’s time for new rotors.