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Low Speed Brake Noise and Downhill Vibration

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Marcius, Sep 12, 2020.

  1. Marcius

    Marcius Junior Member

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    Low speed braking (under 30 mph) produces a sound like a baseball card flipping around the spokes of a bicycle wheel. Maybe not so loud, though noticeable. Sounds like a subtle bop, bop, bop... sound.

    Downhill vibration occurs at higher speeds. The car is new to us, so I've only had it on a minor mountain road once. I was on a long higher speed downhill, and braking once in a while to control my speed. It felt like the front rotors were warped, as the steering wheel started shuddering. I tried isolating the brakes from the regen braking by putting it in N. I did this around my neighborhood, but not on any high speed downhills. The brakes felt fine, but I'm not sure that my test was sufficient. I'm leaning towards thinking that the regen brakes were shuddering that time on the mountain road, and not the rotors.

    Not sure if the two issues are related. Has anyone experienced these problems? What was the outcome?
     
  2. bisco

    bisco cookie crumbler

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    there have been some gen 4 brake issues, i would start with a close inspection. how many miles on her?
     
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  3. Marcius

    Marcius Junior Member

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    Are the gen 4 brake issues to do with the standard brakes, or the regen brake system?

    Mine's a 2017 Touring 3 with 65k miles. We've had it for a few months, and it was quiet at first. Then one day, she said something sounded like a wire smacking around the wheel on her way home from a 10 minute drive. She says "with a bad memory" she thinks that the smacking around sound was mainly on turns. I need to get it on jack stands and see what's under there. I can diagnose regular brakes, but the regen brake system, I know only one thing --> that if you do the brakes, or remove the brake pads, make sure that you disconnect the 12v battery beforehand.
     
    #3 Marcius, Sep 12, 2020
    Last edited: Sep 13, 2020
  4. bisco

    bisco cookie crumbler

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    just the standard brakes. there really is nosuch thing a a regen brake system. when you aren't accelerating, you're regenerating. and even some times when you are.
     
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  5. kithmo

    kithmo Couch Potato

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    Drop it into "B" when descending a long hill and the engine will do the braking.
     
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  6. Marcius

    Marcius Junior Member

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    Yes, I heard that's a good idea once the hybrid battery is fully charged. I'd still like to isolate the shuddering.
     
  7. Marcius

    Marcius Junior Member

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    Yes, I heard that's a good idea once the hybrid battery is fully charged. I'd still like to isolate the shuddering.
     
  8. Marcius

    Marcius Junior Member

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    There's a good discussion about the "Low Speed Noise," which seems to be my problem. Here's the link:

    Clicking Sound on Regen Braking
    https://priuschat.com/posts/3076705/

    Not sure if my downhill shuddering is related to the discussion in this link, but the low speed sound seems possible.

    Had I found the above link first, I would have posted there instead of starting a new thread.
     
  9. kithmo

    kithmo Couch Potato

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    If you put the car in "B" it will eliminate the brakes AND the regen. You have said it doesn't do it in "N" so you have already eliminated the brakes, so if it does vibrate in "B" theres no regen, so it's the transmission, if it does not vibrate in "B" then it's the regen.
     
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  10. Marcius

    Marcius Junior Member

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    I just read the following analysis regarding "B" mode:
    http://techno-fandom.org/~hobbit/cars/b-mode.html
    Seems that B mode does not completely eliminate regen.
     
  11. kithmo

    kithmo Couch Potato

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    Ok, it was just a suggestion.
    As you're obviously researching your problem elsewhere on the internet and not open to trying suggested solutions, I will let you get on with it. I hope you find what you're looking for. :sleep:
     
  12. ChapmanF

    ChapmanF Senior Member

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    B doesn't eliminate regen on mine either.
     
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  13. Marcius

    Marcius Junior Member

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    Thanks for the confirmation. It's certainly good to know that before I go about road testing again.