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Parking Brake moderate incline

Discussion in 'Gen 3 Prius Technical Discussion' started by DeezPrius, Jan 28, 2019.

  1. DeezPrius

    DeezPrius Junior Member

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    Putting the vehicle in neutral w/ the parking brake on, should it be able to hold my Prius because its not working for my vehicle.
     
  2. Grit

    Grit Senior Member

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    Super dangerous as they would consider that in here and hv battery could run out.

    Not a smirky question but what’s the task on hand to park brakes on N?
     
  3. DeezPrius

    DeezPrius Junior Member

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    @Grit ... just to check if its working.

    It kinda defeats the purpose of the user using it without no knowledge of it actually working as it should.
     
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  4. sam spade 2

    sam spade 2 Senior Member

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    There likely is some way to adjust the "grab" of the parking brake.
    After 8 years, it likely needs some adjustment.
    Typically, the cable stretches over time.

    But then, it might also depend on your definition of "moderate".
     
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  5. Grit

    Grit Senior Member

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    I use mine all the time flat or not, when you park on a decline or incline and just use normal park, you feel a slight forward or back motion after you set to P w/o park break. When you park break, there’s no forward or back slight motion if you set park break w/break pedal in the correct order.
     
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  6. DeezPrius

    DeezPrius Junior Member

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    Yes i understand,but were just using "P". I just want to know if my parking brake does need adjustment and if so how can i tell if need one, hence the parking brake on an incline.
     
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  7. DeezPrius

    DeezPrius Junior Member

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    I was able to test the parking brake on a very minimal grade, and it worked. I will adjust when I upgrade my brakes next month.
     
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  8. gliderman

    gliderman Active Member

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    You test a parking brake by putting the brake on and putting it in gear and tap the gas pedal and if the vehicle moves, it is not holding enough to pass the Texas State inspection.

    YMMV
     
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  9. ASRDogman

    ASRDogman Senior Member

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    The parking brake SHOULD hold the car. The "P" is for the transmission, and is NOT designed to hold the car.
    I've never experience it, but have heard of cars getting "tapped" and it braking the parking paw, and then the car roles.
    Best to set both. At least every owners manual says to do that. :)
     
  10. ChapmanF

    ChapmanF Senior Member

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    The US requirements for any car that has a transmission "park" mechanism as well as a parking brake are found in the Federal Motor Vehicle Safety Standard 105, S5.2.2.1, S5.2.2.2, and S5.2.2.3:

    • When both the parking brake and the transmission park mechanism are applied, the car has to stay put for 5 minutes on a 30 percent grade, forward or backward (subject to the limits of tire friction).
    • When the parking brake is applied but the transmission park mechanism isn't, the car has to stay put for 5 minutes on a 20 percent grade, forward or backward.
    • When the transmission park mechanism is applied but the parking brake isn't, the car must be able to take a 2½ MPH hit front or rear without busting the transmission park pawl and rolling away.

    So, yeah, if your parking brake can't meet the standard, it ought to be diagnosed/adjusted/fixed.
     
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  11. Elektroingenieur

    Elektroingenieur Senior Member

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    The point is quite valid, but FMVSS 105 applies to vehicles “with a GVWR greater than 3,500 kilograms (7,716 pounds)” (§ 571.105 S3). For passenger cars, see instead FMVSS No. 135, Light vehicle brake systems, and FMVSS No. 114, Theft protection and rollaway prevention. The parking brake holding test in FMVSS 135 S7.12 has similar criteria, but the transmission “park” test in FMVSS 114 S6 isn’t as strict.
     
  12. fuzzy1

    fuzzy1 Senior Member

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    Were any of those cars Prii? Earlier discussions indicate that the Prius pawl is quite robust. When towing a Prius out of tight corners or when the ignition cannot be turned on (to reach Neutral), it is quite normal to just drag the car with tires skidding.
     
  13. ChapmanF

    ChapmanF Senior Member

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    Thanks for pointing that out. I think I've made the same mistake before, in some earlier PC post that I can't find now. I had noticed S5.2 (a) talked about vehicles 4,536 kg or less, which seemed right to me, but I had not flipped back the six pages to see there was a minimum GVWR given in S3.

    So the parking brake criteria seem to be five minutes on a 20% grade forward or backward, without regard to whether the transmission is in park, and the parking pawl criteria require nothing more than that it keep the car from rolling more than 150 mm when you gently release the brakes on a 10% grade; there seems to be no requirement for what kind of collision bump it can take without breaking.

    Its construction isn't all that different from those in other automatic transmissions I've seen, and there's no particular reason Toyota would have built it any more bulletproof than the regulations require.
     
  14. ASRDogman

    ASRDogman Senior Member

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    This was before the Prius. 20 years ago or so, I can't remember. It wasn't important to me so I didn't care. :)
    I always use the parking brake when I park. And turn the wheels toward the curb if parking on any hill.
    Better safe than sorry. :)
    I've never heard of any vehicle being "dragged" in park and whether or not it broke the paw. I guess it would depend on transmission.
     
  15. fuzzy1

    fuzzy1 Senior Member

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    But you haven't been on PC long. In my decade here, I've heard of it many times.
     
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  16. Mendel Leisk

    Mendel Leisk Senior Member

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    When parking on a steep hill or driveway, I notice I really need to push hard to lock it. Even in Park there's a little slop, and you can feel/hear the difference between locked and slipping.

    Attached is the Repair Manual instruction for parking brake adjustment. I've never looked at ours, maybe a good idea though. I'm guessing it's all good but not sure: cable could stretch a little over time.
     
  17. ASRDogman

    ASRDogman Senior Member

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    I'm talking about ANY car, not just the Prius. They're all pretty much the same.
     
  18. fuzzy1

    fuzzy1 Senior Member

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    I'm talking about what has been posted specifically in PriusChat over my decade here. Just because you haven't seen it in your short time here, doesn't mean it isn't posted here.
     
  19. ASRDogman

    ASRDogman Senior Member

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    This is true.