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2018 Mazda 3 GT - Pulsating brake pedal at highway speeds

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Mike T. · rep 0 · May 25, 3:34 AM · 1 replies · solved · Question

Vehicle: 2018 Mazda 3 Grand Touring

Hey everyone,

I've been noticing a really annoying pulsation in my brake pedal when I'm braking from higher speeds, like on the highway. It feels like the pedal is pushing back and forth rhythmically. It's not as noticeable at lower speeds, but it's definitely there.

My car is a 2018 Mazda 3 Grand Touring with about 65,000 miles on it. I haven't had the brakes serviced in a while, maybe about 20,000 miles ago. I'm wondering if this is a common issue or what might be causing it.

Any thoughts on what could be going on? Should I be worried about this?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:34 AM

0

ClearTheCode admin answer:

This pulsating brake pedal symptom, especially noticeable at higher speeds, is a very common indicator of warped brake rotors. When rotors become unevenly worn or heat-stressed, their surface is no longer perfectly flat. As the brake pads clamp down, they encounter these high and low spots, causing the pedal to pulsate.

Here's what's likely happening and what to do:

  1. Causes of Warped Rotors:

    • Excessive Heat: Repeated hard braking, especially when going downhill or carrying heavy loads, can overheat the rotors. If they cool unevenly, they can warp.
    • Improper Installation/Torquing: If lug nuts aren't torqued correctly or if the wheel hub isn't clean during installation, it can put stress on the rotor, leading to warping.
    • Poor Quality Rotors: Some aftermarket rotors might be more prone to warping under stress.

  2. Diagnostics and Solutions:

    • Inspection: A mechanic will visually inspect the rotors for signs of scoring, discoloration (blue spots indicate extreme heat), and measure their runout with a dial indicator to confirm warping.
    • Replacement: The most common and recommended solution for warped rotors is replacement. While some shops might offer to 'turn' or 'resurface' rotors, this removes material, making them thinner and potentially more prone to warping again or overheating. Given your mileage since the last service, new rotors and pads are likely due.
    • Brake Pads: Always replace brake pads when replacing rotors to ensure even braking surfaces and optimal performance.

  3. When to See a Shop:

    • You should get this checked out as soon as possible. While warped rotors might not immediately lead to total brake failure, they significantly reduce braking efficiency and increase stopping distances. This compromises your safety and the safety of others on the road. A shop can accurately diagnose the issue and perform the necessary replacements.
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