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Did my Model S rapidly accelerate while cruise was on through a puddle?

Discussion in 'Model S: Driving Dynamics' started by Muzzman1, Feb 23, 2015.

  1. Muzzman1

    Muzzman1 Member

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    I searched and was unable to find any discussion regarding this....(sorry if this is a rerun)
    So it rarely rains here in LA. (not gloating) and last night I was driving on the fwy in HOV lane where water tends to puddle.
    Cruise was on, and the car obviously hydroplaned for a moment, and the car lurched forward like I put the go pedal to the wood....it took me by surprise. (scared the crap out of me cause I would normally lift when my cars hydroplane)
    Is that normal behavior?

    I now know that cruise in the rain is not a good idea....

    ....but can anyone explain why the car felt that accelerate was the thing to do?
    My only explanation is the front wheels momentarily had a lower speed relative to the rear so the speed sensor that might be in the front wheels told the computer that the car needed to accelerate in order to meet my speed setting???
     
  2. billarnett

    billarnett Member

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    Maybe the rear wheels spun a little when they hit the water increasing their rotation rate. Then when they got traction again they were going faster than the car and so made a little forward jerk?
     
  3. Runarbt

    Runarbt Member

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    Completely normal, i get this all the time when driving throug puddles with cruise on. A very short acceleration, you feel it and then it is over. Can be a bit scary, but it is so short that it is over almost before you register it.:) and when you know to expect it, no big deal.;-)

    I also get a similar respons driving iver speedbumps with cruise on, weird but also not a big deal.;-)
     
  4. Gizmotoy

    Gizmotoy Active Member

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    Normal. That's why you don't use cruise under slick conditions. A number of years ago my friend smashed his Acura into a jersey barrier on the highway because of this.

    Cruise uses sensors on the wheels to determine the speed. When you hydroplane the wheels slow, and cruise attempts to compensate by accelerating. Not a great situation, especially if the vehicle is RWD.
     
  5. Zextraterrestrial

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    cruise over speed humps ? :biggrin:
     
  6. wk057

    wk057 Senior Tinkerer

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    Yeah, it definitely says to not use cruise in adverse conditions.... but everyone does it anyway.
     
  7. NoMoGas

    NoMoGas Member

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    UGHHH How long before the rain sensors disconnect TACC? That would SUCK!
     
  8. Runarbt

    Runarbt Member

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    We have 40km/h with speed bumps... And i struggle to drive this slow.:) have gotten one speedin ticket for 55km in 40km zone. 2900nok or 400 USD. So i often play safe with cruise.;-)
     

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