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Bike rack - Roof vs Hitch - range difference? Roof details inside

Discussion in 'Model S' started by Proxlamus, Jul 9, 2018.

  1. Proxlamus

    Proxlamus Member

    Joined:
    Jun 11, 2017
    Messages:
    62
    Location:
    Colorado
    Hey guys,

    I have a Model S with a Seasucker bike rack that holds 3. Today I made a short trip to the mountains from Denver to Winter Park carrying 2 downhill bikes on the roof.

    Well my 75D should have a range of 260 miles and I commuted 163 miles with only 24 miles remaining when I got home. Ouch! Now it was 96* F out and air conditioning was on, and it was up and down a mountain pass, so I know itll change the range quite a bit.

    My average energy was 338 wh/mi.

    Anyway, I'm curious how the range is on cars with a Ecohitch and bike rack. I think the roof rack has a massive impact on aerodynamics and I'm *assuming* the hitch wont be as bad and I'm considering making a switch. Any input from those with a hitch rack?

    *picture attached is old, carrying 3* (not applicable to today's adventure)
     

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  2. ewoodrick

    ewoodrick Member

    Joined:
    Apr 13, 2018
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    700
    Location:
    Buford, GA
    I don't know the numbers, but I do know that a number of people highly recommend removing bike racks on ICE vehicles when not in use.
    If an ICE vehicle will feel the difference, an aerodynamic vehicle is definitely going to see it.

    Noe honestly, the heat is probably going to help. A ground elevation of 12,000 ft is going to be the equivalent of 17,000 ft at 98 degrees. It will require more A/C, but that's mighty thin air and will definitely help reduce the vehicle drag. But the going over the pass didn't help.

    Want to get an understanding of how much drag that is? Look at the bikes from the front and guess how much surface area that is. Now cut a piece of cardboard that size and hold it out the window when going 70. Maybe you should start at 30, so you don't break your arm.
     
    • Helpful x 1
  3. Proxlamus

    Proxlamus Member

    Joined:
    Jun 11, 2017
    Messages:
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    Location:
    Colorado
    I'm replying from the hospital now, I tried the cardboard cut out and sticking my arm out the window to hold it at 70 mph and it was like trying to arm wrestle Thor. My arm is broken in 19 places. Remind me not to do that again. ;)

    As for the altitude compensation and air conditioning that's an excellent point. I had not considered that.

    My biggest question is whether placing the bikes on a hitch mounted rack in the rear of the car where the low pressure drag area is would increase my range . I would assume pulling the bikes out of the majority of the slipstream of the car would help? Or would it make the low pressure in the rear become MORE turbulent and have similar or worse performance.
     
  4. icefree

    icefree Member

    Joined:
    Apr 8, 2017
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    105
    Location:
    Northern VA
    #4 icefree, Jul 9, 2018
    Last edited: Jul 9, 2018
  5. Proxlamus

    Proxlamus Member

    Joined:
    Jun 11, 2017
    Messages:
    62
    Location:
    Colorado

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