TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker and becoming a Supporting Member. For more info: Support TMC

Bike rack drain

Discussion in 'The UK and Ireland' started by TooEager, Jan 5, 2020.

  1. TooEager

    TooEager Member

    Joined:
    Aug 21, 2019
    Messages:
    72
    Location:
    Bishop's Stortford
    The drain with a bike rack on was insane. I'm assuming this is because of the impact on drag but it was crazy. Less than half the estimated mileage. More of an fyi than anything else!
     
    • Informative x 3
    • Like x 1
  2. NewbieT

    NewbieT Member

    Joined:
    Aug 16, 2019
    Messages:
    886
    Location:
    North West
    Roofrack or towbar?
     
  3. TooEager

    TooEager Member

    Joined:
    Aug 21, 2019
    Messages:
    72
    Location:
    Bishop's Stortford
    Ah yes. Towbar. Great to be able to take all of the families bikes mind!
     
  4. VanillaAir_UK

    VanillaAir_UK Moderator UK and Ireland

    Joined:
    Jun 17, 2019
    Messages:
    6,633
    Location:
    Surrey, UK
    What sort of conditions, roads, speeds, distance?
     
  5. Cogarch

    Cogarch Member

    Joined:
    Apr 27, 2019
    Messages:
    232
    Location:
    London
    That is really concerning. I waited for the tow hitch precisely because I thought the effect on range would be less than with a roof bike rack. Surely time for a YouTuber to do some comparative testing..!

    However I suppose the effect of having several bikes mounted sideways against the wind must create a bit of an air dam...
     
    • Like x 1
  6. hmy7k

    hmy7k Member

    Joined:
    Nov 7, 2019
    Messages:
    92
    Location:
    Shropshire
    The rear ones are pretty bad I used to see mpg drop heavily on my previous Audi.

    I went for the M3P so I now have a roofbars and Thule carriers, I have fitted them but not used them yet so i haven't been able to compare.

    However, the drag from a bike sideways on will be greater than one facing the front I would have thought.

    I also found the rear carrier meant the wheels sticking quite a long way out to the sides of the car which you had to be aware of on narrow roads.
     
    • Informative x 1
  7. Cogarch

    Cogarch Member

    Joined:
    Apr 27, 2019
    Messages:
    232
    Location:
    London
    My theory -- doubtless incorrect -- was that the airflow behind a Kamm back is fairly chaotic and so putting a bike there would be have less of an effect that sticking it up on the roof...
     
    • Like x 1
  8. Jason71

    Jason71 Active Member

    Joined:
    May 8, 2019
    Messages:
    2,286
    Location:
    Shropshire
    Are we talking motorway speeds here? In which case I am not surprised. I imagine the effect is much much greater at high speed
     
    • Like x 1
  9. ckarner

    ckarner Member

    Joined:
    Apr 30, 2019
    Messages:
    24
    Location:
    Massachusetts
    I move bikes with them on the roof and have not experienced much effect on range.

    Bike top.jpg
     
    • Like x 3
    • Informative x 1
  10. westrow3

    westrow3 Member

    Joined:
    Aug 13, 2019
    Messages:
    79
    Location:
    Southampton
    What roof bars have you got? The OEM ones are pricey are there any other options?
     
  11. hmy7k

    hmy7k Member

    Joined:
    Nov 7, 2019
    Messages:
    92
    Location:
    Shropshire
    I bought the OEM ones, I don’t think there are any other options unless you are prepared to use suction fixings on the glass roof.

    it worked out cheaper than the towbar option if I had bought an LR.
     
  12. Adopado

    Adopado Active Member

    Joined:
    Aug 19, 2019
    Messages:
    2,832
    Location:
    Scotland
    Looking on youtube the fitting of the roof bars looked quite scary ... digging into the seal at the edge of the glass roof. I'm not looking for roof fittings but I can see the attraction of the suction type.
     
  13. hmy7k

    hmy7k Member

    Joined:
    Nov 7, 2019
    Messages:
    92
    Location:
    Shropshire
    First time I put them on I was a bit wary, but having done it a couple of times now it’s pretty straightforward, putting clips in is easy, main thing is not to over tighten. There is actually no contact between bars and glass roof, the clips go into a slot in the body below the glass.
     
  14. Jason71

    Jason71 Active Member

    Joined:
    May 8, 2019
    Messages:
    2,286
    Location:
    Shropshire
    That is the theory, and I am happy it's working out for you, but there are some youtube tails of woe out there that put me right off
     
  15. hmy7k

    hmy7k Member

    Joined:
    Nov 7, 2019
    Messages:
    92
    Location:
    Shropshire
    Perhaps you could share these, I watched a number before buying and they were consistent with how I have found them.

    Are you suggesting they damaged their roof?
     
  16. webbah

    webbah Member

    Joined:
    May 22, 2012
    Messages:
    903
    Location:
    Lucerne, Switzerland
    I’m using the OEM roof racks myself. I’d be more wary about the suction cup ones damaging the glass roof (many reports of these cracking just from flex/roll during spirited driving already). I’ve installed and removed these carefully at least 10 times to use them when required with my Thule Motion XT Large storage box. No issues at all as long as you install them according to the instructions and confirm they are fixed to the mount points. That said, I have not noticed much of a reduction of range with just the OEM racks on the car as they are aerodynamic in a sense, but I remove them when I won’t need them for awhile as I prefer the look of the car without them.
     
    • Informative x 1
  17. TooEager

    TooEager Member

    Joined:
    Aug 21, 2019
    Messages:
    72
    Location:
    Bishop's Stortford
    Apologies for missing the notifications. This was on the rear and at fairly slow motorway speeds like 65mph
     
  18. Avendit

    Avendit Member

    Joined:
    Apr 18, 2019
    Messages:
    678
    Location:
    EDI
    I'm not looking forward to my first trip with our 4 bikes on the back tbh. I already used to do things like orientate saddles to face forward, remove MTB mud guards and so on, but I do wonder if it will be enough. I wondered if disrupting the air flow at the top of the back window with a small wedge would force the worst of the air up and over the bikes rather than having them in the main stream of 70mph wind? Would it help? or would it just be the same? beyond my aerodynamics knowledge.
     
  19. Andrew_SE23

    Andrew_SE23 Member

    Joined:
    Jul 3, 2019
    Messages:
    123
    Location:
    London
    I would have thought that the bikes create a very turbulent airflow behind the vehicle and, consequently, low pressure behind the vehicle (because the air can no longer flow in a laminar manner around the vehicle body). This means there will be a pressure drag - high pressure in front and low pressure behind - which is why it is so inefficient.
     
  20. Avendit

    Avendit Member

    Joined:
    Apr 18, 2019
    Messages:
    678
    Location:
    EDI
    Absolutely, but can adding a wedge early in the roof line cause a smoother (and therefore more efficient) flow around the bikes. Essentially creating a low pressure zone of chaotic turbulence for them to exist in, rather than them causing such a zone. If I get time I'll try and draw some pictures later...
     

Share This Page

  • About Us

    Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.
  • Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


    SUPPORT TMC