Brake rotors are a fundamental part of any disc brake system. Although rotors are typically made from durable cast iron, they can eventually develop uneven wear that causes the brake pedal to pulsate. That wear is often referred to as “warpage”.
When the rotors become warped, you’ll likely notice one or more troublesome symptoms that you’ll want to address right away.
What is a Warped Brake Rotor?
Brake rotors (also known as brake discs) are found in disc brake systems. Most vehicles have disc brakes at all four corners (one behind each wheel), though some have discs in the front and drums in the rear. When you apply the brakes, a pair of brake pads squeeze against the rotor, creating friction and slowing the corresponding wheel to halt the vehicle.
The term “warped rotor” is often used to describe a rotor that’s worn in such a way that it causes a pulsating brake pedal. In reality, however, the rotor isn’t actually warped but has excessive thickness variation (parallelism) or rotational side-to-side movement (runout). Still, it’s common for both vehicle owners and professionals to refer to the problem as warpage.
Common Warped Brake Rotor Symptoms
Do you think you might be dealing with a warped brake rotor? If you notice one or more of the following symptoms, you might be right.
Note: Other problems can mimic warped brake rotors. You (or your mechanic) should perform a thorough diagnosis before conducting any repairs.
Pedal Pulsation While Braking
The most common sign of warped rotors is a pulsation felt in the brake pedal while braking. Why does this happen? Because the uneven surface finish kicks the brake pads out and away from the rotors.
Vibration in the Steering Wheel While Braking
In some cases, you might also notice that the warped rotors cause a vibration that’s felt in the steering wheel while braking.
Abnormal Noises
Rotors with uneven surface wear can make a chattering noise when contacting the brake pads. You might also hear a clunking noise when the brakes are applied.
What Causes a Brake Rotor to Warp?
Numerous reasons may cause the rotor to warp. Most of them involve poor driving habits, neglect of the vehicle, and wear and tear.
Overheating
Warped brake rotors are often caused by overheating. This is because each time you step on the brakes, the brake pads create friction with the rotor, which results in heat. Excessive heat may eventually cause the steel rotor to bend.
Hard Braking
Similar to overheating, hard braking generates friction and heat. The main difference between the two is hard braking accelerates the process, while overheating is simply a result of wear and tear.
Lack of Maintenance
Due to wear and tear, brake pads are susceptible to thinning. This leads to overheating, which is often followed by a bent rotor.
It’s crucial to always have the brake pads and the brake system as checked during your scheduled vehicle maintenance.
Driving on Rough Roads
Driving on rough terrain and uneven roads put stress on the brake rotors, which may cause them to warp. Similarly, speeding through potholes and bumps has similar effects.
Manufacturing Defects
While rare, some vehicles have manufacturing defects that prevent certain components from working properly. A poorly made brake rotor is more prone to bending due to heat and stress.
Frequently Asked Questions
Usually, you’ll feel the pulsation from a warped rotor while braking, but not while driving with your foot off the brake pedal.
Do you feel a pulsation while braking, indicating your car’s rotors might be warped? Some say that you can tell whether the front or back rotors are to blame by noting the origin of the pulsation.
The theory is that the front rotors are likely to blame if the pulsation is felt in both the steering wheel and the brake pedal. On the other hand, if the sensation is only felt in the brake pedal, the rear rotors are probably at fault.
Another popular test method involves applying the parking brake while coming to a stop. If the pulsation goes away with the parking brake applied (which affects the rear brakes), the front rotors are likely warped.
Unfortunately, these assessments aren’t always conclusive. The most accurate way to determine whether the front or rear brakes are causing a pulsation involves performing a visual inspection, then measuring the rotors for parallelism and runout. Parallelism is measured with a micrometer, while runout is checked with a dial indicator.
But very few technicians (and even fewer DIYers) make an effort to measure parallelism and runout. Instead, most just make an educated guess as to which set of rotors should be serviced or replaced.
In some cases, you can have a professional resurface (machine) a rotor to fix a warpage problem. But the rotor must be replaced if it’s visibly damaged or resurfacing would cause it to fall below the minimum thickness specification.
You can typically expect to pay somewhere between $100 and $200 to have a professional resurface your car’s rotors; replacement usually costs between $300 to $600. Of course, the exact cost of the repair will depend on various factors, such as the type of vehicle you have and the repair shop you choose.
If you have the tools and the know-how, you can save money by replacing the brake rotors yourself with products from CarParts.com.
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Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.
I’ve been driving and working on vehicles since high school and learn new things all the time. It’s a pleasure to read from a perspective of a Master Service Technician, with cycles, cars. Boats. Planes and big trucks always changing its hard to sometimes keep up. Looking forward to phasing into hydrogen power in all engines, it’s cleaner, safer, more powerful and a great deal cheaper when on demand.