Brake Pedal Pulsation While Braking: a Common Culprit

By Vlad Samarin December 3, 2023
Many motorists have experienced this problem: The brake pedal pulsates when braking. This problem is often caused by one common culprit. In this article, we'll look deeper into this issue.

Warped Brake Rotors and Rust Spots:

Background: Brake rotors are subjected to tremendous heat and wear during regular use. Over time, this exposure can lead to uneven thickness across the rotor surface, creating what we commonly refer to as warped rotors. One common reason that can exacerbate overheating of the brake rotor is a seized brake caliper.

Additionally, rust spots can develop on the rotor surface, especially when a car is parked for extended periods in wet weather without movement. This causes parts of the rotors to rust and become thinner, also resulting in an uneven thickness.

Identifying Warped Brake Rotors and Rust Spots: The common symptom is a rhythmic pulsation in the brake pedal during braking. More noticeable at higher speeds, the pulsating sensation signals irregular contact between the brake pads and the uneven rotor surface.

Rust spot on a brake rotor Rust spot on a brake rotor.
If there are rust spots on the rotor surface, you may also hear a rythmic thumping noise when braking. This often happens after the car has been parked for days in wet conditions without movement. In some cases, you can actually see rust spots on the rotor through the wheel.

If the front brake rotors are severely warped or rusted, you may also feel that the steering wheel starts shaking when braking.

Some cars have rear drum brakes. Unevenly worn or warped drums can also cause brake pedal pulsation.

Solution:

Rotor/Drum Resurfacing or Replacement: Seek the expertise of a trusted mechanic to assess the extent of rotor warping and to inspect other parts of the brake system.
Resurfacing a brake rotor Resurfacing a brake rotor.
For minor warping, rotor resurfacing might restore evenness. In cases of significant warping, replacing the rotors will be required to restore optimal braking performance.

For every car, manufacturers specify minimal rotor thickness and maximum rotor runout. If the rotor is worn out close to the limit, it must be replaced.

In case of the rear drum brakes, the working surface of the drums will need to be inpected. Drums can also be resurfaced or replaced. Car makers specify the maximum allowable brake drum diameter. If it's worn close to the maximum diameter, the drum must be replaced.

Address minor rust spots by driving the car regularly, allowing the friction from braking to remove surface rust. If severe, consult a professional for evaluation.

Cost: Rotor resurfacing typically ranges from $60 to $200 per pair, while rotor replacement costs can vary from $150 to $300 or more.
Add the price of the brake pads ($35-$120 per axle) if they are worn out and also need to be replaced.
In the case of the rear drum brakes, resurfacing cost will be the same: $60 to $200 per pair. Replacing rear brake drums will cost from $150 to $350.

Brake Caliper Issues: In some cases, overheating of the brake rotors can be caused by a seized or faulty brake caliper. All brake calipers need to be checked during the professional brake inspection. Replacement costs vary based on the type of caliper and can range from $120 to $450 or more per caliper.

Conclusion: Regular brake system inspections and timely maintenance, coupled with awareness of signs like pulsations, ensure a safer and more efficient braking experience. If you notice the telltale pulsating sensation, consulting with a professional mechanic will help identify the extent of rotor warping, rust spots, and caliper issues, implementing the necessary solutions for optimal brake performance.