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Did my brakes fail????

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Barnetto, Oct 16, 2013.

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Did my brakes fail????

  1. Yes

    0 vote(s)
    0.0%

  2. No

    5 vote(s)
    100.0%
  1. Barnetto

    Barnetto New Member

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    I have a 2008 Prius. Had to do an 'emergency' stop. Put my foot on the brake pedal REAL hard and the car slowed way down, but not down enough. Munched the front end. Now remembering back, I didn't feel any 'chattering' from the ABS brakes. It seems like I got regen braking but never switched to the hydraulic brakes. Is that possible? Did I experience a braking failure? Or do Prius just take a lot longer to stop? I did a test stop in the rental car I have now (not a Prius or hybrid), and it gives me the ABS chatter as I would expect, with a short stopping distance. Any ideas?
     
    #1 Barnetto, Oct 16, 2013
  2. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    In a panic stop, the friction brakes will always be engaged. Even without power. As long as you applied over 500 newtons of force, the friction brakes were engaged. If you panic stopped with less than 500 newtons of force, unless there was a total system failure which has never happened you had hydraulic assist friction brakes as well as the regen brakes. There is always a first time for complete failure with no self diagnostics, but consider it extremely unlikely since it would be the first case in 5 million vehicles.

    "Remembering back" doesn't work with humans. Your brain cannot cope with the shear volume of data your sensors are spewing. Your brain will try to speed up and categorize what it can (where the feeling of "time slowing" is thought to come from) but it will never be able to remember everything.

    Add to that, the only reason you will get stuttering on the brake line is if the ABS detects wheel lock. The "chatter" is releasing the brakes then reapplying something that humans in a panic are also really crappy at doing so the computer takes over. You do not want chatter. Chatter proves the ABS is working, but only because you locked the wheels in the first place.

    The make and model of car doesn't matter as much as the make and model of tire. If you have poor balding tires, you aren't going to stop worth $hit. If you have new sticky tires, you will stick to the road like glue and tear your face off.
     
    #2 2k1Toaster, Oct 16, 2013
  3. zhenya

    zhenya Active Member

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    What was the speed? What were the conditions like? What were the condition of your tires?

    As said above, it's not impossible that your brakes failed, but extraordinarily unlikely. Hydraulic brakes are extremely reliable and by design almost never fail completely.
     
    #3 zhenya, Oct 16, 2013
  4. Barnetto

    Barnetto New Member

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    #4 Barnetto, Oct 16, 2013
  5. Barnetto

    Barnetto New Member

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    Actually I think you DO want "chatter". If you apply enough force to a hydraulic system the wheels should lock up. Then the ABS does it's thing to release and reapply the brakes (in rapid succession - hence the chatter) to prevent wheel lock and tire skid. So without "chatter" I'm stuck wondering if there was a disconnect between the relative regen and hydraulic applied forces (which is all computerized). I agree memory is often tainted, but not always.

    I have 'new' Michelin tires with about 10K miles on them. Dry pavement, clear skies, about 40 mph.
     
    #5 Barnetto, Oct 16, 2013
  6. fuzzy1

    fuzzy1 Senior Member

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    The pulse rate on my Prius is usually far higher than on my older ABS car, fast enough that I don't even perceive it as 'chatter'. Only in some circumstances does it get slow enough to feel like the old style 'chatter', usually it is fairly smooth.

    (I'm not voting, for lack of sufficient information to judge.)
     
    #6 fuzzy1, Oct 17, 2013
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