Signs of Warped Rotors
Arguably more important than the ability to accelerate and steer your vehicle is the capacity to bring your vehicle to a stop. A disc braking system is designed to use friction between brake rotors or discs and brake pads. One common issue you could experience is warped rotors, and the symptoms can make your drive less than comfortable.
The correction for warped rotors can be machining them to regain a flat, consistent surface again, but the best solution is to replace both brake rotors on the affected axle. With an average cost of $60 to $150 per pair, it’s a relatively cost-effective fix. But what is a warped brake rotor, and how do you identify its symptoms? Here’s what you should know.
What Is a Warped Rotor?
A brake rotor is designed to look like a wide-brimmed hat. The center of the hat, or the face of the rotor, is centered on the wheel studs and/or the axle hub flange. The ‘brim’ is the rotor’s working surface, and it’s a perfectly flat, hardened steel surface where the pads press against when the caliper squeezes closed. Some brake rotors have a ventilated section between the inner and outer surfaces to dissipate heat, as is the case with front brake rotors. Most rear brake rotors are a solid surface without ventilation.
But if the rotor has lateral runout, meaning that the surface is no longer completely flat and true as it passes between the brake pads, it’s considered to be warped. To put it into perspective, you might begin to feel the symptoms of warped rotors with as little as 2/1000ths-inch of runout.
Why do Brake Rotors Warp?
Generally, brake rotors don’t actually get hot enough to warp from the heat alone. Rather, what happens are a few conditions that change the rotor’s contact surfaces to cause the uneasy feeling of warpage.
Severe heat conditions are one of the main reasons that rotors warp, but it’s not because the rotor’s shape distorts as you’d think. When brakes get very hot, the rotor’s surface actually softens. Then, when the brakes are applied, the brake rotor surface wears down in areas of lower density rather than the brake pad getting worn. It results in disc thickness variation, and some spots are physically thinner than others on the rotor. When the brake pedal is pressed, the caliper piston moves in and out at a rapid pace to compensate for variances. Sometimes you’ll see bluing on the rotor face.
The second reason for the feeling of warped rotors is that the rotors are glazed. This happens when brake pads and rotors have reached extreme temperatures and the pad material has become embedded into or coated portions of the rotor. These areas have a differing amount of friction than normal, so it gives the feeling of a warped rotor.
Signs of a Warped Brake Rotor
If you have one or more warped brake rotors, there are a few common symptoms you’re likely going to detect.
- Brake pedal vibration. When you press the brake pedal, it can feel like chattering through the pedal that varies with your vehicle speed. The higher your rate of speed, the faster the vibration’s frequency. It’s common to feel brake pedal vibration when any brake rotor is warped, whether at a front or rear wheel.
- Vibration through the steering wheel. Especially for warped rotors on the front wheels, you could feel a vibration that jitters the steering wheel side to side.
- Noises while braking. You might hear a rhythmic groaning or thumping noise when you brake. It’s due to an uneven surface for the brake pads to apply against.
- Failing or sticking calipers. If rotors are warped, the additional strain on calipers to compensate can cause them to fail.
How to Replace a Warped Rotor
Changing a warped brake rotor is one of the simpler DIY repairs you may take on. It’s non-intrusive and usually takes around an hour to change both of the brake rotors on an axle. The process varies depending on the vehicle you drive, but generally, these are the steps.
1. Lift and secure your vehicle
Lift the affected wheels off the ground and secure them on jack stands. If need be, you can lift one wheel at a time to complete the job. Make sure to set the parking brake and chock the wheels.
2. Remove the wheel
Loosen and remove the lug nuts, then take the wheel off the hub and set it to the side.
3. Remove the caliper and bracket
Find the appropriate socket or wrench and remove the brake caliper. Suspend it with a strap or bungee cord so it isn’t hanging from the brake hose.
4. Remove the rotor
There may be clips on the rotor to remove first, which a pair of sidecutters is perfect for. Then, get the rotor off. Most rotors will slide off the wheel studs without much effort, although some need to be removed using a puller or by whacking the face of the rotor with a hammer to dislodge it.
5. Install the new rotor
Clean the new brake rotor with brake cleaner and wipe it dry with a lint-free cloth. Then, slide it onto the wheel studs until it’s firmly against the wheel hub flange. It’s the perfect time to install new brake pads too. Check the brake fluid level and top it up from a new container, if necessary.
Install the brake caliper and the wheel, tightening each to the correct torque spec. Then, lower the car to the ground. Pump up the brake pedal until it’s firm, then start the engine and press the brake pedal a few times until it feels normal. Then, carefully road test to ensure the brakes are operating as designed.
For new brake rotors, shop at AutoZone. You’ll find all of your brake parts, fluids, and any tools you need to get the job done right in one place. If you decide that it’s too big a job to tackle on your own, let AutoZone help you find qualified professional mechanics through our Shop Referral Program.
FAQ/People Also Ask
No, it’s very unlikely you’ll feel a vibration when you aren’t braking due to warped rotors.
It isn’t a good idea to drive with warped rotors since it can cause longer stopping distances and loss of control on wet or loose driving surfaces.
Warped rotors can make a squealing noise with a varying pitch and frequency, or it can sound like a low-pitched growl.
Rotors can be ‘turned’ or machined to restore a flat surface of uncontaminated metal. However, the faster and often cheaper solution is to replace them with new brake rotors.