Here’s a novel concept: Disc brake systems contain brake discs, which are also referred to as rotors. Like brake pads, rotors are considered wear items that require periodic replacement.
I change my car’s brake rotors every time I swap out the brake pads. That way, the new pads and new rotors mesh together in harmony from the beginning.
Last month, while rebuilding the front end of my Astro Van, I found the front brake pads to be extremely worn. So, I ordered a new set of pads and a pair of rotors online and—voila!—they appeared on my porch within a couple of days.
Even though repair shops often resurface rotors instead of replacing them, modern rotors are affordable enough that I opt for a new set every time. Who wants to stand around hunched over a brake lathe anyway?
Some people argue that you don’t always have to service the pads and rotors together. But I’ve done it that way my whole life. To me, spending a little extra money on new rotors is worth it because, well, your brakes are extremely important.
You May Have Faulty Brake Discs If…
Brake rotors are simple components with a rather limited list of common symptoms. Some signs your rotors may be worn include:
- Vibration or Pulsation: Worn brake rotors often cause a pulsation or vibration while braking. The sensation is felt in either the steering wheel or brake pedal.
Why does this happen? The rotors become worn unevenly over time. As a result, the pads bounce up and down over the high and low spots of the rotor surface.
- Abnormal Noise: Rotors with uneven surface wear can make a chattering noise when contacting the pads. You may also hear a clunking noise when the brakes are applied.
- Wear Beyond the Manufacturer’s Recommendation: Your brake rotors and pads mesh each time you hit the brake pedal. Because of this, both wear down over time. That’s why professionals measure rotors for thickness whenever a brake check is performed.
If the rotors are worn beyond the manufacturer-recommended minimum thickness, they must be replaced. This specification may be stamped into the front of the brake rotor, or it can be found in your vehicle’s factory repair information.
- Reduced Stopping Ability: An uneven rotor surface can push the pads away from the rotor, creating excessive clearance between the components and a low brake pedal.
- Visible Imperfections: Do the rotors have cracks, hard spots, deep scoring, or heat discoloration? Then they should definitely be replaced.
What Does a Brake Disc Do?
There are two different types of braking systems: disc and drum. As was mentioned, disc brake systems rely on disc-shaped brake rotors for stopping power. All modern cars have front disc brakes and many have disc brakes at all four wheels.
Brake rotor operation is straightforward. When you press the brake pedal, pressurized hydraulic fluid flows from the master cylinder and acts on the brake calipers. Each of the brake calipers contains a set of brake pads that squeeze against the brake rotors, creating the friction needed to stop your car.
What to Do If You Think You Have a Bad Brake Rotor
You don’t want to take any chances with your brakes. If you suspect that you have bad brake rotors, diagnose and repair the problem right away.
In some instances, a brake rotor with an uneven or marred surface can be refinished, rather than replaced, to restore proper operation. But if a rotor is worn beyond specification—or machining it would take it beyond that point—it must be replaced. A rotor must also be retired if it suffers from flaws that cannot be corrected during the resurfacing process.
And one more thing: You should always replace rotors as a pair to ensure optimum braking ability.
Products Mentioned in this Guide
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.