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Prospective Owner - Help me design my driveway!

Discussion in 'Model S: Ordering, Production, Delivery' started by Boatguy, Aug 16, 2014.

  1. Boatguy

    Boatguy Member

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    Can't buy a Tesla until I have a place to charge it! So I'm completely rebuilding my house, with a new garage and driveway. The driveway i the challenge as it's got to climb from the street to my house.

    Does anyone know the approach and departure angles with the standard car, no air suspension?

    How often do you scrape the nose or tail?

    Thank you!

    Russ
     
  2. jerry33

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

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    I don't know the exact angles, but it has to be really steep before I do any scraping (air at standard height). My driveway has a steep angle to the curb and I never scrape. What I'd suggest is looking around and finding a commercial driveway that looks about as steep as your prospective driveway and then get a test drive and try it.

    You might be able to get some idea from this photo. (Raining right now, so I can't just snap a new one.)

    driveway.jpg
     
  3. paulkva

    paulkva Member

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    I have air suspension, and at standard height I have no problems on a short but somewhat steep driveway. Max grade at my house is 15%.
     
  4. youlikeadajuice

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    I had a "driveway situation" at my house and attempted to do some research before I got my car back in Feb 2013. I opted for an air suspension car so that I could get up my driveway and into my garage, and although I was close, I wasn't quite able to manage it with the air suspension alone. The pictures below will give you some idea, but I don't have problems at the bottom of the driveway (street to driveway), but had a problem at the top (driveway into garage). On my very first attempt getting into the garage, I had my fiance outside watching the bottom of the car...front tires got in, but just about at the middle of the car, the car touched the concrete at the threshold of the garage opening. I was so close, but couldn't bear to scrape every time I went in and out of the garage and didn't want to risk doing any damage.

    I came up with a not so elegant, but effective solution of placing ramps made of 2x12's just inside the garage that essentially keep the front of the car going "up" inside the garage long enough for the center of the car to clear to avoid high centering. Once the car is past the critical point, the ramp goes back down and the car makes it all the way in. I may someday see if I can have my driveway slightly regraded, but for the past year and a half, this has worked flawlessly as long as the car is in the "very high" setting. I guess the point is that I know my driveway is just barely past the limit of what car can handle as far as high centering on a driveway, however, I don't know the exact angle. If anyone knows a quick way to determine this, I'd be happy to provide the info...I'll try to take some measurements a little later and dust off my geometry skills and see if I can at least provide you with a close estimate of the angles of my driveway. In the meantime, here are some pics:


    photo 1.jpg photo 2.jpg photo 3.jpg photo 4.JPG
     
  5. tezzla

    tezzla Member

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    The car on coil springs is very similar to the air on the high setting.
     
  6. Tmoody

    Tmoody Member

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    Check with your local building code authority. Many jurisdictions maintain a max df 13-14 degree slopes which is right on the verge of scraping front air dams of many sporty Euro type sedans and/or sports cars. For general rule and piece of mind, I would recommend a max of 10 degree slope.
     
  7. Boatguy

    Boatguy Member

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    Since this is new construction I need to reduce this to numbers for the builder. If you have an iPhone, the included Compass application has a nice level (swipe to the right from the Compass screen). If you could measure the street where it meets your driveway, and your driveway, that would be very helpful.

    Thanks!

    - - - Updated - - -

    Is the street level at the transition to the driveway, or does it dip down to a gutter?

    - - - Updated - - -

    This is great information! The high centering you describe is also called the break over angle and I had not considered that to be an issue since usually the approach or departure angle is less than the break over angle and the bigger problem.

    Since this is new construction I need to reduce this to numbers for the builder. If you have an iPhone, the included Compass application has a nice level (swipe to the right from the Compass screen). If you could measure the street where it meets your driveway and your driveway, that would be very helpful. I assume that your garage is essentially flat (or has a 1/8" / 12" slope to the entrance).

    Thanks!

    - - - Updated - - -

    I've spent a half hour with an engineer from the city and other than the ADA sidewalk requirements, there are no hard and fast rules. They have some guidelines which are basically a 16% maximum slope (9.1 degrees), but it's only a guideline and as you point out the 16% might not work for all cars. I'm following the old adage to "measure twice, cut once" which is even more critical when working with concrete!
     
  8. jerry33

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

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    The slope is nine degrees.
     
  9. Boatguy

    Boatguy Member

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    I assume the street is flat where it meets your driveway. That's a 16% grade which is consistent with the guidelines.

    Thanks for the help!
     
  10. jerry33

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

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    the driveway actually goes into an alley rather than a street. The alley has a V shape so the part where scraping might occur is in the centre of the alley rather than the driveway to alley intersection. The garage is flat with a 3 cm bump up. No problems there either. The only place I've had trouble at standard height is at my father-in-law's house where there is a steep angle for about 0.75 metre. Even then, I've only scraped with a full load when I forgot to set the suspension to high. Now I know the air suspension should keep the same height, but the suspension travel will be larger with a heavy load. Can't measure that as it's 1000 km from here.

    Here a thread with some numbers (repeated below)

    Approximate length from tip of front bumper to front wheel: 33 inches
    Approximate length from tip of rear bumper to rear wheel: 36 inches

    Low air suspension height: 5.2 inches
    Standard air suspension height: 6 inches
    High air suspension height: 6.9 inches
    Very high air suspension height: 7.3 inches

    Standard approach angle: ~10.4 degrees
    Standard departure angle: ~9.5 degrees
     
  11. Boatguy

    Boatguy Member

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    Looking more closely at your pictures, It looks like your driveway is much steeper at the top than the bottom, and then there is a large lip on the garage floor which is effectively a much steeper slope.

    The effective slope of your driveway would be measured by putting a board between the lip on the garage floor and 5'-6' down the driveway.
     
  12. Boatguy

    Boatguy Member

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    The V shape means that the grade break is not the full 16% of the driveway since the front wheels are already on a grade when the nose is over the 16% driveway. Those V's are usually fairly steep so the true grade break may be more like 10%, thus no problem. Good data in any case and thanks for the clarification!

    Ha ha! These are from a post I made earlier this year. The measurements are from a Tesla tech with a ruler and compass, they are not official numbers from engineering.
     
  13. paulkva

    paulkva Member

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    Basically no dip. The whole driveway is only 32' long from street to garage entrance, it's all asphalt, and it's a smooth transition from the street. Even though the grade peaks at 15%, it's somewhat gradual getting to 15% from either end.
     
  14. youlikeadajuice

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    Boatguy, sorry it took a few days to get back to you...good call with the compass app! I put down a 6' long board from the lip of the garage down the driveway and got 15 degrees as an angle. Did the same at the bottom from the street up the driveway and got 8 degrees. You are right that the driveway is not a straight angle, it has a bit of a "U" shape to it, as well as my street being on a slight incline and curve, and the lip at the top, so there's a lot going on here. Hopefully these general numbers will be of some help though.
     
  15. Boatguy

    Boatguy Member

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    Very helpful! I calculated the break over angle at 11 degrees which explains why you have problems with a 15 degree break over at the top of your driveway. The 8 degrees at the bottom compares to an expected 10.4 approach angle which again explains why you have no problem there. Thanks!
     
  16. mhpr262

    mhpr262 Member

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    The obvious solution would be to arrange for a test drive and simply try it out - veeeery very carefully. That shouldn't be too difficult if you live in San francisco. Maybe you needn't change anything at all.
     
  17. Boatguy

    Boatguy Member

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    Test drive really won't work in this situation. Here is a picture of my driveway as of four days ago.

    2014-08-13 130427.jpg
     
  18. tezco

    tezco Sig P85

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    Looks like you're building a sileage pit. How organic!
     
  19. Boatguy

    Boatguy Member

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    Today I received an official reply from Tesla on the various angles. Here is the data for anyone who may have this issue in the future.

    Please note that the below information is for the Coil Suspension and an unladen vehicle. Loading up the car will naturally change the clearance levels and the related angles. I’d also advise airing on the side of providing extra clearance whenever possible.

    Approach Angle = 12.8 degrees (23% slope)
    Departure Angle = 14 degrees (25% slope)
    Breakover Angle = 11.1 degrees (20% slope)
     

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