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Hydroplaning

Discussion in 'Model S: Driving Dynamics' started by Fezzik, May 30, 2015.

  1. Fezzik

    Fezzik P67429

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    Has anyone ever had a bad hydroplane in the MS? I just finished watching a video and saw a Toyota on an interstate driving slowly hydroplane badly, go sideways and then hit the concrete barriers. I've hydroplane in other cars slightly when it was raining real bad bud had control of the car. I am assuming since the MS is a lot heavier it will break through the water maybe. Just curios on other people experiences and ideas on it in the MS
     
  2. vvanders

    vvanders Member

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    I can't speak to the non-D variants but I found the 85D to be pretty stable at 65-70 when hitting large patches of water. As with any car the trick is to keep the inputs steady and not make any sudden movements until you have traction again.
     
  3. BerTX

    BerTX Member

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    Weight is only one of about 10 factors influencing hydroplaning. It can certainly help compensate for the other factors, but to say that hydroplaning is less likely because it is a Tesla would be stretching it a bit, although it might recover more gracefully. Tire design and wear and inflation, road surface, water depth -- too many factors are not vehicle dependent.

    Hydroplaning happens because the tire can't push the water out of the way fast enough. The best way to control hydroplaning is to slow down.
     
  4. DavidB

    DavidB Aug 2013 S85

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    I have experienced some hydroplaning in my Tesla. The worst case happened when I knew there was water on the road (it was raining), but I wasn't expecting the large puddle, about two car lengths long, that I hit. As has already been said, the best way to control hydroplaning is to slow down--preferably even before the hydroplaning occurs. Once you are hydroplaning, as already said, keep the inputs steady and not make any sudden movements until you have traction again. In this case, I knew I was drifting out of the lane, but I kept my wheels pointed in the direction my car was heading until after I regained traction, and then easily returned back to the center of the lane.
     
  5. BerTX

    BerTX Member

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    Ha, yes, I meant slow down to avoid hydroplaning, thanks...
     
  6. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    hydroplaning occurs when the pressure in the wedge of water that builds up in front of the tires is equal to the inflation pressure.

    Deep tread helps reduce the pressure up to a point, and tread compounds can help as well, but keeping the pressure up is really the key. Because it's often cooler on rainy days, the pressure you set on a sunny day might be too low for a rainy day. (Of course, slowing down is highly recommended)
     
  7. BerTX

    BerTX Member

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    My first reaction was "no, tire pressure is just one factor", but then I thought about it a bit more. Heavy vehicles have higher tire pressures, so maybe that is a reason they are less prone to hydroplaning. The higher the rate of speed, the higher will be the pressure of the water in front of the tire, so even a properly inflated tire can hydroplane. Good tread design will help reduce the pressure of the pushed water. Worn tires will cause the water pressure to build up quickly, so they are very prone to hydroplaning.

    I still think that, as you say, tire pressure is important, but having a worn tire at high speed, even if properly inflated, will still end in disaster. I'll go along with tire pressure being key, but maybe not "the" key to preventing hydroplaning.
     
  8. Fezzik

    Fezzik P67429

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    Great discussion. Reason I'm asking is that I used to drive a 76 buick electra... Talk about a heavy car. I never hydroplaned in that car. I completely agree good tire pressure and tread is the key factor, but I always found that I hydroplaned less in that buick than I did a 85 honda accord I had or the 82 chevy cavilier when I was young. I have not experienced hydroplaning in the S yet.
     
  9. yobigd20

    yobigd20 Well-Known Member

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    i've only lost traction with the goodyears, they suck. the michelin pilot sport A/S 3 hold extremely well no slip at all holds great in rain .
     
  10. JMG

    JMG Member

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    Since it has practically rained here in Texas since January 1st, I can attest that the Model S handles water great, at least in my experience. Of course it's new tires, but vs my old Tahoe it felt much more stable hitting patches of water on the highway versus the Tahoe.
     
  11. RDoc

    RDoc S85D

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    I was just on a highway trip in heavy rain and had a couple of very brief hydroplaning incidents, but while I could feel the car go light, it always was under good control. On one occasion, it was a bit more significant and the car beeped (traction, stability assist?) but completely stayed in control.
     
  12. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Slowing down is the real key, but aside from that once the tread grooves get filled it's inflation pressure. Of course the shallower the grooves the quicker they get filled up, but in the end it comes down to the pressure in the wedge of water vs the inflation pressure.
     
  13. RDoc

    RDoc S85D

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    This is correct, kind of by definition. If the water pressure is greater than the tire pressure, the tire is not touching the road surface, it's planing on the water, and water doesn't withstand sidewise force very well at all. That also leads directly to the tread design factor. The rain sipes and other features in the tread pump the water out from under the tire to attempt to minimize the water wedge build up. Don't go out in the rain with slicks on your car.

    My understanding is that there's been some real advances in tread design for rain using computer modeling.
     
  14. David99

    David99 Active Member

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    I'm not sure this makes sense. Hydroplaning happens when the water can't be pushed out of the way fast enough. But I don't see how tire pressure would make any difference. The weight of the car determines how much force pushes down on the wheels. When hydroplaning happens the car is basically lifted up but it has nothing to do with tire pressure as it's the car's weight that determines the pressure. To give an example, even if the car had solid steel tires (virtually infinite tire pressure), hydroplaning would happen at the same speed.
     
  15. RDoc

    RDoc S85D

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    I doubt that very much.

    Steel wheels, assuming the pavement were hard enough that the deformation was mainly in the wheel, would have a very small contact patch because the weight of the car would be supported on a much smaller area, so the water on the road surface would be squeezed out very effectively. Pressure is weight dived by area (lbs/sq in) so it's not just the weight of the car, it's also the contact patch area. If you decrease the tire pressure, the contact patch area has to go up because it still has to support the same weight. But that means that the same water pressure which formerly couldn't lift the car, now can, so the car will hydroplane, that is, it will become water borne.

    Consider skipping a stone across a pond. If you have a wide thin stone, throwing it flat side down, as opposed to on edge, will skip much more easily even though the weight of the stone is the same. The difference is that the weight is spread out over a larger area when flat side down, so the pressure, weight per area, is much less.
     
  16. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    This is correct, but most water still flows north to south (the direction of the circumference) rather than east to west (across the width of the tread). The big advancement has been in the irregularities to break the surface tension of the water.
     
  17. From our Tech article on the subject (which mirrors the valuable input already offered);

    The speed at which a tire hydroplanes is a function of water depth, vehicle speed, vehicle weight, tire width, tread depth and tread design. It depends on how much water has to be removed, how much weight is pressing down on the tires and how efficient the tread design is at evacuating water. While deeper water, higher speeds, lighter vehicles, wider tires, less tread depth and less efficient tread designs will cause tires to hydroplane at lower speeds; all tires will be forced to hydroplane at some speed.


    As a rule, tread design affects hydroplaning resistance at high speeds and in deep water. Tread compound affects wet traction at lower speeds or in shallow water.


    Directional tread designs (sometimes called Unidirectional tread designs) are frequently used on tires intended to better resist hydroplaning. Their multiple tread grooves are aligned in a repeating "V" shape to increase the tire's ability to channel water from between the tire's footprint and the road. Somewhat like the vanes of a water pump continually pushing water in one direction through the engine, the grooves of a directional tire are designed to push water in one direction through the tire (forward on an angle to the sides). Directional tread designs are especially helpful in increasing hydroplaning resistance when relatively wide Plus Two, Plus Three or Plus Four tire and wheel applications result in fitting a much wider tire to a vehicle than its Original Equipment size.

    Since nearly all the options we have for Model S are non directional, that last bit is more of an FYI.
     
  18. GloriaL

    GloriaL Member

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    Two questions; if you remove your foot from the accelerator pedal while hydroplaning will the regenerative braking engage? And if so does that change the drgree/duration of hydroplaning?
     
  19. S4WRXTTCS

    S4WRXTTCS Active Member

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    That's a good question because with regen enabled the electronics will try to do regenerative braking, and I don't care what people say it's going to be really hard not to suddenly let off the accelerator during a hydroplaning event.

    I don't think we really hear much about a Tesla MS hydroplaning because it's such a massive car, and the drivers tend to have good tires. It also has some of the worst windshield wipers on the road which leads to people slowing down.

    Where the biggest issue in the rain is the braking effectiveness since a person rarely uses the brakes, and not using brakes in the rain leads to bad situations. So in the winter I might end up having regen set to low.
     

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