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Dirty Butt

Discussion in 'Model S: Interior & Exterior' started by Cerie, Dec 2, 2014.

  1. Cerie

    Cerie Member

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    I've noticed now that the weather has become gloomier and the ground is covered with a mix of powdered salt and rainwater that the Model S tends to kick up a lot of that grossness onto its own backside. Is this due to its aerodynamic shape or because there is no exhaust to "blow away" the ick? Next up on features: a protective bubble surrounding my car that protects it from the outside world (think hamster wheel) but until then, weekly car washes it is!
     
  2. liuping

    liuping Active Member

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    Black dusty road grime shows on my Model S's "backside" all year round here in San Diego. I think you are right about the aerodynamics.
     
  3. FLDarren

    FLDarren Member

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    That's usually the dirtiest part of my car besides behind the tires. I have the LED license plate bulbs and they really let the dirt show at night.
     
  4. JakeP

    JakeP S P4996 / X P6028

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    I use a California Car Duster to keep that back end clean, it is amazing how much dust adheres back there. A combination of airflow and electrostatic adhesion, I would wager.
     
  5. Newscutter

    Newscutter Member

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    Even more interesting (to me) is how CRISPLY the road grit will deposit itself on the trailing edges-- like pin striping!

    See pic (I can't get it to embed)
    Tesla Pittsburgh on Twitter:
     
  6. Todd Burch

    Todd Burch Electron Pilot

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    A little aerodynamics:

    Ironically, a more aerodynamic back side should lead to less dirt on the tail, since better aerodynamics would imply less of a pressure drop immediately behind the car, which in turn would have less of a vacuum effect to suck grime onto the tail.

    However, having said that there are a few factors:

    1) Yes, the shape of the rear seems to cause air patterns that tend to pull dirt up off the road and onto the tail. All Model S's are subject to this. (It's ok...AFAIK we still can claim the lowest drag coefficient of any production car).

    2) The smooth underbelly of the car causes more laminar (smooth) flow underneath, as opposed to an ICE which causes more turbulent flow. This yields better aerodynamics, but may also contribute to the "coordinated" lifting of grime from the roadway.

    3) A possible contributing factor: The high torque produced at low speeds coupled with the lack of mud flaps may fling more grime up, and since this happens at low speeds, there is less surrounding airflow to blow the grime away from the car.
     
  7. JakeP

    JakeP S P4996 / X P6028

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    Oh I like the laminar flow explanation, that makes good sense.
     
  8. Todd Burch

    Todd Burch Electron Pilot

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    Update: Paying more attention to the geometry of the body around the rear wheels, I'd say my theory in #3 above is an unlikely contributing factor--so #1 and #2 seem to be the primary causes.
     
  9. RiverBrick

    RiverBrick Active Member

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    #9 RiverBrick, Dec 2, 2014
    Last edited: Dec 2, 2014
    Even considering the RWD?

    When driving over snow, the license plate can quickly become blotted out. I'd rather not get stopped for a warning for this. Is there a more convenient solution than frequent cleaning stops?

    Just in case someone's not familiar with the phenomenon, here's an image lifted from the Cross Country Rally video.

    Snowed out license plate.jpg
     
  10. ecarfan

    ecarfan Well-Known Member

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    I think every car I've owned has attracted more dirt at the rear than the front. I know my Roadster, Porsche Cayman, Porsche 356A, Toyota Prius, Subaru Forester, Mini Cooper and Ford Merkur all have displayed that characteristic. The Model S seems typical in that regard.
     
  11. Barry

    Barry Member

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    They make automotive toilet paper for that :smile:
     
  12. JakeP

    JakeP S P4996 / X P6028

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    What are your thoughts on electrostatic influence? The motor and drive train are within inches of that rear cowling, and I know they are magnetically shielded, but I still can't help but think this is a contributing factor. The way that back end is a dust magnet just makes me think "static cling"!
     
  13. Todd Burch

    Todd Burch Electron Pilot

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    Interesting thought, but I doubt that plays any factor.
     
  14. green1

    green1 Active Member

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    I'm with ecarfan on this one... show me a car that DOESN'T have this issue. I've never seen one.
     
  15. liuping

    liuping Active Member

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    You could be right, it may just be more noticeable to me since this is my first white car.
     
  16. ecarfan

    ecarfan Well-Known Member

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    @liuping, four of the seven cars I listed in my post were white or very close to it, and I certainly noticed the greater amount of road grime in the rear compared to the front. I always wash my cars myself, I never take them to a car wash, so I do take note of where the dirt is.
     
  17. ecarfan

    ecarfan Well-Known Member

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    (Deleted, inadvertent duplicate post, sorry)
     
  18. mknox

    mknox Well-Known Member

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    Yes, but it is definitely worse on the Model S than anything else I've driven. Not really an issue except that it really interferes with the rear view camera. Even if I wipe it off, it's blocked again within a few miles on salty/wet winter roads.
     
  19. Cerie

    Cerie Member

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    I didn't mean that this is the first car I've had where the back gets dirty but all my other ICE cars have gotten dirty near the sides or the bottom bumper. I just noticed that the Model S tends to really KICK that dirt up all the way up to what would be the trunk part of a non hatchback.
     
  20. green1

    green1 Active Member

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    There are really only 2 solutions to help keep the back of a car clean.
    1) mud flaps. The bigger the better.
    2) wind deflectors, you see these occasionally on station wagons, mini-vans, and SUVs, most are useless, but some direct air down the back just right to keep it clean.
     

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