2018 Prius Brake problem 35K miles

Discussion in 'Gen 4 Prius Main Forum' started by ralphgonegolfing, Jul 6, 2019.

  1. L.V. Raiders

    L.V. Raiders New Member

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    2018 Prius
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    Two
    I experienced strange braking behavior on a recent trip, similar descriptions on this thread. I've had warped rotors on an F150 in the past but I haven't driven my prius in any similar conditions which would have caused warping.

    Last month I was driving a long downhill section of highway with tight turns. I was stuck behind a car which was taking the turns very slowly, so we would speed up then hit the brakes pretty hard. Conditions were cold and dry, but there had been snow in the area the week before. At first, the brakes performed normally, but then about 1/2 way down the hill the car would shake violently when I applied the brakes. This is the one and only time I've experienced this. It cleared up and even with hard braking on highway or city I haven't felt it repeat.

    The feeling was very similar to when I had warped rotors on the F150, but my dealer explained it as just ABS kicking in. I will admit that compared to my 2012 prius with Michelins, this 2018 with stock tires will engage ABS much more frequently - particularly in city driving. But when the shaking occurred I was too preoccupied with driving to notice whether the ABS light on the dash was turned on. Looking forward to getting new tires as these stock shoes are pretty awful.

    I'm going to just monitor this and see if it repeats, but thought I'd add to this thread in case others experience similar behavior.
     
  2. FuelMiser

    FuelMiser Senior Member

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    I believe what you experienced is called brake fade--the reduction in stopping power that can occur after repeated or sustained application of the brakes. The pads and rotors heat up and rather than grabbing, they just slide, kind of like butter sliding around a hot pan. Perhaps this didn't affect both sides equally, and caused the ABS to kick in (which pulses the brakes) when one wheel sped up compared to the other. This explains why the condition cleared up after the brakes cooled down to normal temp. This sounds like a situation to use the B mode to add engine braking when running downhill. The only other "cure" is to pull over and let the brakes cool down. Pikes Peak Highway in Colorado has a brake check station on the way down to make sure brakes don't overheat and become dangerously useless on the way down. They also warn about using a lower gear (B mode in the Prius).
     
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  3. L.V. Raiders

    L.V. Raiders New Member

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    Interesting - thanks for that input. It does sound consistent with the symptoms. I'll keep an eye on it, and definitely agree the B mode is really helpful. Cheers.
     
  4. kithmo

    kithmo Couch Potato

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    Sounds normal to me, if braking hard. On regen braking the ABS doesn't apply until the hydraulic brakes kick in, if one wheel lets go then it feels like the car is surging forward, you then brake hard and the hydraulic brakes and the ABS kick in quite violently.
     
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