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My Hydroplaning Experience in MS 85D

Discussion in 'Model S: Driving Dynamics' started by ansetou, Oct 10, 2016.

  1. ansetou

    ansetou Member

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    Before I start to describe my experience, I’d like to say the purpose of this post is to help everyone, including myself, understand the safety features of our beloved Teslas. As such, let’s try not to get distracted by the moral of my driving behavior or other things that are not directly related to the design/behaviors of the car and physics.

    ****************
    This past weekend was a rainy one probably for many living along the east coast of USA. NYC was no exception. In the early Sunday morning I drove through Brooklyn with my wife. My incident happened when we were on BQE (I278). If you are familiar with NYC highways you'd know how narrow the lanes can be and how bad the road condition is. The part where it happened probably had about 2 foot gap from side of the Model S (a very wide sedan) to the lines on each side. And NO shoulder.

    I was traveling maybe 70~75 mph at the moment (not smart) while it was steady raining (not pouring but more than just dripping). And I was shifting from center lane to right lane trying to go around a slow moving car. I remember that was a pretty big SUV. The right lane had a wall next to it without any shoulder. Shortly after I got to the right side of the SUV, I found myself hitting a pot of water (which I couldn't see before I changed lane) and started hydroplaning. It still puzzles what actually happened the next few seconds so here I am seeking help from the crowd wisdom.

    (A little background of myself as a driver. I have been driving move than 15 year and have always been an aggressive driver. I have certainly had my shares of hydroplaning in the past. In almost all cases it was easy to recover from it except once a few years ago my hydroplaning in a different car resulted in it spinning and ultimately flipping over. So I'm very familiar with the feeling of hydroplaning. )

    As the hydroplaning started happening on Sunday morning, I first felt a shock in my steering wheel probably from the uneven resistance the front tires experienced from the water. Then the car start to slide a little. My first instinct was trying to keep the car going straight through that tight channel between the SUV and the wall to my right. And I did that by slightly steer it in the opposite direction of the sliding. All of a sudden I started to feel strong torque coming from my Model S' steering wheel that's much stronger and sharper than the typical force you'd feel from water. What was even more weird was in the next few seconds the direction of the force kept on changing btwn left and right and did so many times. The whole time I was fighting it and still try to steer the car straight. This must have lasted more than 5 seconds which felt like eternity (my wife later recalled it to be 30 seconds :). During the whole time I was concerned about applying brake could make the situation worse so I kept my speed and eventually slowly passed the SUV as the car regained stability.

    Although visually I didn’t see myself hitting either that SUV or the wall, I swear I heard a dull knocking sound from the back during that process. After it was all over, I thought I must have hit something on one side but continued driving as I didn’t otherwise feel the car was damage in a way that would affect its driving. When we got to our destination about ½ hour later, I got out and checked the car and did a walk around. Nothing. No scratch or whatsoever.

    As much as I’d like to give myself the credit for a perfect handling of the situation, I honest thought the chance of that is very slim given how narrow the available path was and how fast the car was traveling. As such, I was trying hard to think whether some part of the car’s intelligence helped. My car is a late 2015 version 85D with autopilot. I recently upgraded to version 8.0. So here are a couple of my theories:
    1. Basic stability control kicked in and helped straighten the car by braking on each side as it was sliding. Each brake plus my steering probably overdid it and required a counter-reaction from both the machine and me until the tires eventually regained grip of the ground. I think this was the most likely case.
    2. I believe the car has side impact detection using its parking sensors (sonnet?) and maybe the radar in the front. If that was properly designed it could potentially increase the precision of the correction it applies to the wheels and the brakes.

    What do you think? Anyone had similar experience? Any Tesla engineer here?
     
  2. habanero69

    habanero69 I Dont Need Cialis. I Drive an EV.

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    The "shock" you first felt in the steering wheel was most likely the car realizing you were making a lane change without using a turn signal and crossing a painted line; a vibration is sent/felt thru the wheel to alert the driver. Other than that, I dunno...
     
  3. lolachampcar

    lolachampcar Active Member

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    I've never had one of our MS' move with water but my rear wheel drive McLaren has an astounding ability to bring the back of the car in line using differential braking when breaking traction in a straight line in the rain. The car has a relative low polar moment and the brakes are there almost as quick as my counter steer.

    I have looked at MS' traction control on launch and found Tesla has the ability to adjust power much much faster than any ICE. Given the speed of individual caliper reaction as demonstrated by the McLaren combined with Tesla's ability to modulate fore and aft power, I'd say stability control kicked in in a big way and it was/is the dynamic response of the system that made it feel so strange/different from your previous experience.

    I'd say it is time for some CPR (correct, pause and recover) on a wet skid pad for you with your MS. Best to learn the beast in a safe environment so there are no surprises in the real world. Just a suggestion; no scolding intended.
     
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  4. ansetou

    ansetou Member

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    I hate that "feature" and always had it off.
     
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  5. ansetou

    ansetou Member

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    thanks. sounds like you essentially agreeing with my theory #1 but added very good technical details. And no scolding taken :) wonder where I can find a skid pad nearby NYC. i had that experience when I took delivery of my prev bimmer from factory delivery. it was fun.
     
  6. ansetou

    ansetou Member

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    btw, if that's indeed the cause of my perfect escape, I'd say it's very well designed. the room for error in that situation was very small.
     
  7. habanero69

    habanero69 I Dont Need Cialis. I Drive an EV.

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    I like it, and I don't. ;) For the occasional reminder I may have drifted while having eyes improperly focused off the road, in his situation, I would not...
     
  8. ecarfan

    ecarfan Well-Known Member

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    @ansetou, what kind of tires are on your Tesla, how many miles are on them, and how much tread depth do they have?
     
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  9. maximus16

    maximus16 Member

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    Almost same situation (15' 85D) but I was in AP at the time of hydroplanning. (Was going straight, no lane changes). AP handled it so perfect (never disengaged), my passengers all said WTF just happened, as they knew something happened but weren't sure. You could literally feel each wheel independently doing its own thing, with the dash flashing the traction control warning. Incredible feeling.
    I pulled my dash cam footage but never did anything with it as you couldn't tell...
    I should note that my 21" tires were nearly bald and were actually scheduled to be replaced in two days.
     
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  10. Xenoilphobe

    Xenoilphobe Active Member

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  11. Dithermaster

    Dithermaster Member

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    It sounds like the stability control kicked in, because the wheel speeds differed enough for it to think one or more was slipping.

    The first time I juiced my (RWD) P85+ around a wet corner I was really surprised by the abruptness of the stability control braking, and it's loud too, which could account for the noise you heard.
     
  12. trils0n

    trils0n 2013 P85

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    Sometimes when stability control/traction control activates when one wheel is slipping it can make a loud clunk or knock sound when the brakes suddenly activate to slow down a wheel. (I've tested it by going too fast through an empty parking lot on a rainy day and purposely aimed the passenger side wheels through the standing water to see what would happen -- surprised me how quickly the car detected wheel slip and corrected, the sound it made was also surprisingly loud)
     
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  13. byan1232

    byan1232 Member

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    Wait wait wait... is this true? If we have that feature on the steering wheel will vibrate???
     
  14. thimel

    thimel Member

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    Yes, it is true and useful. To me, it seems like I hear it, but Tesla says it is produced b vibrating the steering wheel.
     
  15. u00mem9

    u00mem9 Member

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    -spits coffee onto monitor-
     
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  16. skhenry81

    skhenry81 Member

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    I have that feature on my 2010 BMW 750i...
     
  17. ecarfan

    ecarfan Well-Known Member

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    Still hoping for an answer to the question I posted over a month ago...
     
  18. 3Victoria

    3Victoria Member

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    I was told this story: a man and his daughter were traveling in their Mini at 45 mph on a two lane snow covered highway following a truck that had left ruts in the snow. He decided to change lanes, and immediately found himself traveling sideways ar 45 mph. He was awestruck, but before he could react, the car righted itself and he was again traveling straight. His dgtr said "What was that?" and he said "The car fixed it" and she said "Yeah, I know, you didn't do anything!"

    Pretty amazing technology ... the car knew that want happened did not correspond to his steering commands and took action to correct the cars orientation.

    Got to love my BMW Mini.
     
  19. bradhs

    bradhs Member

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    I've experienced this in a BMW X5, basically it hooked the car by clamping down on individual brakes to bring the car back to center. It took a while to execute but it eventually did. I can see this being an issue

    I think I've experienced the same situation as OP, but in a much more forgiving environment on the freeway. The steering feel felt like I lost power steering for a sec or that the tires were under tremendous sideways pressure. Completely freaked me out but the car recovered with no issues.
     
  20. Great Dane

    Great Dane Member

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    #20 Great Dane, Nov 24, 2016
    Last edited: Nov 24, 2016
    15 years driving
    hydroplaned before
    driving 70 - 75 MPH
    IN THE RAIN.
    I see cars in ditches every time it rains.
    Time to slow it down when it rains.
    Hope I don"t come across to obvious.
    Please don,t wreck your beautiful Tesla
    Aggressive driving also increase stress.
    I drive aggressive on rare occasions
    When I am running late,and it is really draining
    on me and the Battery.
     
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