What would cause my brake pedal to act like ABS is on? | FerrariChat

What would cause my brake pedal to act like ABS is on?

Discussion in 'Technical Q&A' started by 24000rpm, Feb 27, 2019.

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  1. 24000rpm

    24000rpm F1 Rookie

    Aug 31, 2012
    4,649
    China and California
    #1 24000rpm, Feb 27, 2019
    360 f1.

    Even if I am idling and foot on brake ( lightly , not firm on brake), occassionally the brake pedal will act as if the ABS pump is on.
    when driving normally, the abs comes on way early/easier than expected.

    What could cause this? Bad abs unit? Bad booster?
     
  2. Ferrari_Doctor

    Ferrari_Doctor Rookie

    Feb 14, 2012
    24
    #2 Ferrari_Doctor, Feb 28, 2019
    Have your wheel speed sensors looked at.


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    ernie likes this.
  3. 24000rpm

    24000rpm F1 Rookie

    Aug 31, 2012
    4,649
    China and California
    #3 24000rpm, Feb 28, 2019
    I did. there's no noticeable problem at the sensor cables.

    Is it possible that these sensors themselves go bad?

     
  4. Ferrari_Doctor

    Ferrari_Doctor Rookie

    Feb 14, 2012
    24
    #4 Ferrari_Doctor, Feb 28, 2019
    The sensors can fail. If one of the sensors can’t read the speed it will show 0-kmph so when you hit the brakes at say 30-kmph 3 of the sensors are showing that speed and one at 0-kmph which the abs module thinks the vehicle has one wheel locked in turn activating the abs.
    You require diagnostics to check these. I would certainly start here quite possible that the abs module has failed. More than likely due to poor serviceability of the brake fluid.


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    ernie and 24000rpm like this.
  5. tazandjan

    tazandjan Three Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    38,051
    Clarksville, Tennessee
    Full Name:
    Terry H Phillips
    #5 tazandjan, Feb 28, 2019
    Tire/wheel sizes that differ from OEM Front/Rear tire diameter ratio more than around 4-5% can give those symptoms, too.
     
  6. thorn

    thorn F1 Rookie
    Silver Subscribed

    Aug 7, 2012
    3,322
    Tallahassee, FL
    #6 thorn, Feb 28, 2019
    A good tech with an o-scope (or similar tool) can check the wheel sensors.
     
  7. AmerKhan

    AmerKhan Rookie

    Sep 11, 2017
    3
    Full Name:
    Amer Khan
    #7 AmerKhan, Feb 28, 2019
    You might have warped brake rotors
     
  8. Sled Driver

    Sled Driver Formula Junior

    May 13, 2010
    494
    Stokesdale, NC
    Full Name:
    Emery
    #8 Sled Driver, Mar 22, 2019
    The fact is in EVERY case of "warped brake disc", whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures.
     
  9. johnk...

    johnk... F1 World Champ
    Owner

    Jun 11, 2004
    10,655
    CT
    Full Name:
    John Kreskovsky
    #9 johnk..., Mar 22, 2019
    Generally a bad sensor will not trigger the ABS. If you have a bad sensor the ABS light should come on. Been there.
     
    Rifledriver likes this.

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