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My Cali wouldn't stop

Discussion in 'California(Portofino)/Roma(Amalfi)' started by Tides, Jan 24, 2016.

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  1. Tides

    Tides Karting

    Sep 5, 2015
    53
    #1 Tides, Jan 24, 2016
    So - first time out in the sub 50 degree weather - drove in sport for about a mile of stop start driving - did a u turn on main road - lights changed and applied brakes at about 30 mph - brake pedal was hard but minimal stopping power- engine in 3rd wanted to keep going - pushed harder - still not stopping. - eventually I crawled across red lights somewhat in disbelief - continued on and applied brakes - all was normal. Not sure what happened but it may just been cold brakes or maybe momentary insufficient vacuum to apply servo - Had a car been in front of me at lights I may have just rear ended it. - Phew - shivers down spine. - Any thoughts anyone


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  2. vjd3

    vjd3 F1 Rookie
    Owner Rossa Subscribed

    Jun 3, 2005
    2,750
    Massachusetts
    Full Name:
    Vic
    #2 vjd3, Jan 24, 2016
    Possibly the "ice mode" in the Bosch ABS system is the culprit ... if you google that you will get a lot of hits. Symptom is a very hard brake pedal with little happening. I believe the solution is to take your foot off the brake and then reapply or pulse gently. Hard to do in the heat of the moment.

    "Ice mode seems to happen when the ABS system is running at its maximum to prevent any particular wheel from locking-up. It is venting pressure to allow some wheel rotation, but at the same time trying to apply pressure many times per second. This deadlock scenario results in virtually no braking effect.

    The finger seems to point to the ABS controller, which is unable to meet the demands of all the sensors and inputs, some needing braking force applied others released. These sensors include, brake switch, pedal, accelerometers, yaw sensors and wheel speed sensors. When the system is working so hard to prevent locking of multiple wheels, it doesn't permit enough force to be applied to the remaining wheels to have any affect in slowing the car. The ABS is simply at the limit of its design in these situations."

    See this thread:

    http://www.ferrarichat.com/forum/458-italia-488/494537-intermittent-brake-failure-458-a.html#post144081179
     
  3. Tides

    Tides Karting

    Sep 5, 2015
    53
    #3 Tides, Jan 24, 2016
    Interesting - thanks for reply. - ironically I used to be an early ABS brake engineer - can't see the system not failing in safe mode - lack of grip triggers the ABS otherwise brakes keep applying . I think that the " hard pedal" may well be a clue here and it also is a common denominator in past threads - there is no stored brake boost energy - if the engine is not producing vacuum to provide negative pressure assistance , then u will get no brake assistance - the hard pedal with little if any pedal travel is the classic result and I can think of no other reason for this condition to occur - ABS will bleed pressure to a wheel but not cause a "hard pedal". please someone correct me if I'm wrong


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