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Brakes Grab

Discussion in 'Gen 4 Prius Main Forum' started by GeoinLB, Jan 9, 2017.

  1. GeoinLB

    GeoinLB Junior Member

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    I've had my new 2016 Prius since September 2016 and have driven it about 5000 miles. I have noticed that the brakes grab and it's a bit unsettling. The grab at any speed and seems that if you push the pedal slightly harder they grab, so poor modulation. I've never felt this in any other car that I have driven. Anyone else experiencing this issue?
     
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  2. bisco

    bisco cookie crumbler

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    welcome!
    yes, it's pretty common. keep in mind, prius uses the motor generator to regenerate electricity to the battery, reducing the use of friction pads and rotors. however, have you had any rain or humidity? they tend to grab more because the rotors rust.
    also, there can be a grabby feeling when they switch from regeneration to friction braking around 6 mph.
    something you can try is putting it in neutral at 20-30 mph in a safe area and applying the brakes gently to work the rust off the rotors.
    if nothing helps, take another one for a test drive at the dealer to compare.
     
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  3. GeoinLB

    GeoinLB Junior Member

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    Thanks for the quick response bisco Oh and yea, we've been having some rain for a couple weeks, yep in drought stricken Ca.
     
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  4. bisco

    bisco cookie crumbler

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    all the best!(y)
     
  5. MichelleStone

    MichelleStone Senior Member

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    Prius is famous for this "feature." Fortunately, I was aware of it when I bought my car so I wasn't surprised by it. I could have been really upset had it been otherwise. The brakes will also grab like that on you if you let the car slow itself down with one of the automated safety features.
     
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  6. GeoinLB

    GeoinLB Junior Member

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    You mean that other thing on the gear shift? I haven't tried that yet. I keep forgetting to read about it in the manual. I can't fit the manual in the glove box so it's at home
     
  7. bisco

    bisco cookie crumbler

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    no, not the 'B' mode on the gear shift. that's only for descending mountains. a 'lower gear' if you will, for engine braking, to save your friction brakes.
    michelle means advanced features that automatically apply your brakes. they are not available on the 2016 package 2, i don't believe.
     
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  8. kithmo

    kithmo Couch Potato

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    The Prius is equipped with emergency brake assist, meaning if you press the brake pedal quickly (not necessarily hard) then the brake force is assisted. This can feel like a grab. So maybe you are too quick on the pedal.
     
  9. GeoinLB

    GeoinLB Junior Member

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    I don't think I'm too quick on the pedal, I drive a car with brakes like this. My prior car was an X5 and the brakes were far superior with excellent modulation. But even when I drove loaner 3 series BMW with regenerative braking they didn't grab like this. Personally I think it's a poor and to an extent, unsafe design or lack of design. Btw, my wife has felt the grabbing as well as a passenger and when she drove the car. But at this point there isn't much that can be done.
     
  10. bisco

    bisco cookie crumbler

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    agreed. poor design and not much to be done. i stand by my last sentence of post #2 though. swing by the dealer and ask to drive another, and maybe have them drive yours, just to be sure there's nothing wrong.
     
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  11. kithmo

    kithmo Couch Potato

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    Mine don't grab at all unless I brake suddenly and there's no grab on transition between regen and friction.
    As Bisco says, I'd take it in to the dealers, it sounds like a fault to me. You too Bisco if yours do.
     
  12. MrMischief

    MrMischief Active Member

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    yep mine grab as well, so did others on the lot. I'm not sure the reasoning behind it but Toyota seems to prefer that over smooth pedal modulation. The Chevy Volts I drove did not do it or at least not to the extent that the Prius does. You'll get used to it in a few months. I'm closing in on 15k miles and I just recently began to accept that the Prius feels on the verge of unsafe while under braking due to this grabbing and when it decides to let go over rough pavement. Increase your following distance and you'll be OK.
     
  13. kithmo

    kithmo Couch Potato

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    I wonder if it's a US/UK difference in the system or specification, mine are perfectly smooth yet keen when required to be.
    Or maybe it's my size 11s give me more leverage.
     
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  14. bisco

    bisco cookie crumbler

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    i don't even notice it anymore, but at slow speeds, all 3 of mine have felt a little grabby. very difficult to move a few inches when parking. seems like they are either on or off.
     
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  15. Mendel Leisk

    Mendel Leisk Senior Member

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    Once in a long while our third gen seems to completely lose brake modulation, it's either off or ON. Especially just at start up, and in reverse. Backing up, touch the brake, bam.
     
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  16. bisco

    bisco cookie crumbler

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    interesting. is it rust? mine is all the time. when i'm parallel parking, everybody in my car are like bobble head dolls.
     
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  17. Mendel Leisk

    Mendel Leisk Senior Member

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    Wonderful picture. :)

    Not all the time, seems to be the car's programming, nothing mechanical, rotor condition for example.
     
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  18. RCO

    RCO Senior Member

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    Isn't it the addition of friction pad braking to the rotors from then braking that causes the grabbing effect?
     
  19. alanclarkeau

    alanclarkeau Senior Member

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    I think there are at least 4 (probably more) iterations of braking in PRIUS - and working out the changeover point between the 1st and 2nd below sometimes seems a little "interesting" to judge, but I'm confident with it now - day 1 was a bit interesting.

    • REGEN;
    • REGEN+FRICTION
    • PRE-PRIMED then Emergency Braking
    • EMERGENCY

    The last 2 I would assume also use REGENERATION braking, but we're probably not going to split hairs under those situations.

    The only times I felt she didn't do what I wanted is if I take over braking from DRCC braking because, for instance, I'm going to turn and not follow the slowing car in front - the brake seems to disconnect and reconnect.as though it's "closing" one operation and starting another. The other place I've felt it is when the car in front is slowing gently for a reduced speed limit. If I decide that I want to get down to the legal limit, not the car in front's illegal interpretation of the limit - and DRCC is REGENing, but as I touch the brakes, she seems to momentarily let go of the brakes, then resume with what my foot is telling her I want. Lately, I've been using the C/C stalk to reduce the speed instead - works smoother. Mostly.
     
  20. Mendel Leisk

    Mendel Leisk Senior Member

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    This could be a gen 3 only thing too: it's very temporary, very infrequent, just at startup, typically in reverse. First occurrence I was backing up in a parallel park spot; touched brake and stopped so abruptly I was momentarily convinced I'd hit the car behind.