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MPG with bike racks.....

gtvlussogtvlusso Posts: 5,112
edited June 2011 in Commuting chat
I have roof mounted bike racks - Thule 591 pro-ride mounted on thule 861 aero bars.

I already have some trouble getting bikes onto the roof of the car as the vehicle is quite high anyway.....so, I was wondering about a rear mounted boot rack, maybe a permanent mounted one - like the Thule 973....

Any recommendations out there on types or anything to watch for? I have a mixture of MTB and Road bikes to mount up.

Any impact on MPG, should be allot better than the roof mounted racks due to the aerodynamics!

Will probably sell on the 2x 591's anyway, as the vehicle is so damn high! And the roof bars!

Posts

  • EKE_38BPMEKE_38BPM Posts: 5,821
    I can't give you numbers, but bikes on roof racks kill your MPG. I would presume that boot mounted is better and that carried internally would be best (but your family may not be able to fit in the car).

    I've heard that wing mirrors increase drag by about 25% because of the way they affect the airflow along the sides of the car. Explains why F1 cars have such tiny mirrors.
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  • Have you got a tow bar? I keep a Thule G5 on the back of the car most of the time. It tilts to allow access to the boot. I got it so that my wife could use it - the roof mounts were too awkward for her to reach.
  • The RookieThe Rookie Posts: 27,748
    EKE_38BPM wrote:
    I've heard that wing mirrors increase drag by about 25% because of the way they affect the airflow along the sides of the car.
    Its far from that bad, I'll talk to our aerodynamicist at work and clarify what they do cost.....

    I'll also ask him about rear mounted racks, but if all the bike is outside the airflow line of roof (its a tall car) and floor it leaves only the small amount of wheel/tyre at each side.

    Simon
  • GazzaputtGazzaputt Posts: 3,227
    Cycling + have agood review of bike racks in this months issue which shows loss of MPG.
  • SevenfoldSevenfold Posts: 86
    i have a Thule 973 on a Vauxhall Zafira - easy to fit, very secure & works well BUT...fuel consumption is probably 5+mpg worse (diesel). It take 2 people to fit & is quite heavy though the fact that you can open the boot with it fitted (no bikes on it!) is a bonus. Took 3 bikes through France to the Jura mountains in 2009, no issues so i can recommend it.
  • mossychopsmossychops Posts: 262
    Thule Rideon in use here. I do an 180 mile trip to work and back every week, I am amazed that the rideon doesnt affect fuel consumption at all. I havent noticed any difference at all. I use a fuel logging app and can see no difference on here at all usually 37mph combined in a 1.8l Mondeo.

    Bike nor rack touches the car at all. Very stable. Takes the road bike and the full suss. Very impressed. Also has a light bar with number plate on it (obsuring your lights and number plate is illegal and I was a bit worried that with ANPR in use, this might become a favourite offence for traffic cops to "do you" for).

    2011-04-21%25252010.37.56.jpg
  • fossyantfossyant Posts: 2,549
    Roof rack here, and with four bikes on the roof can hammer my MPG on the motorway.

    I have a mid sized saloon, and it knocks off a good 5 mpg if I drive at 70. Keeping the speed down to 60ish, then it's only a couple of MPG. It's petrol, and keeping the RPM below the magic 3000 seems to help.

    At Easter, we came back from N Wales into a horrendous headwind - even doing 60, I got less than 30 mpg with the rack.

    Very little effect at normal road speeds though.

    Lifting the rack on and off the car takes two people though - aero bars plus the 4x Halfords Advanced racks (Thule)
  • MonkeyMonsterMonkeyMonster Posts: 4,628
    I too would be in the camp of rear rack would hurt the mpg far less than top. Even the rack mounts can cause massive amounts of drag too - more than a few mechanics over the years have told me always to take em off.
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  • The RookieThe Rookie Posts: 27,748
    fossyant wrote:
    even doing 60, I got less than 30 mpg with the rack.
    :lol: One of my cars does 25mpg ave, the other 20mpg, if I attach a bike rack will I get to you just less than 30? :lol:

    Simon
  • ste_ste_ Posts: 124
    Thule aero bars and rack with 1 road bike on the roof knocks circa 5mpg off my X5.

    Am taking the bike to Southern France in August and have been considering a rear rack for just the reason of the increased economy.

    What worries me though is even a small tap from a car behind would write your bike off. :?

    I also like the roof mount - the bike is completely out of the way of the boot, plus it's what the pro teams use ain't it. 8) :D
  • mossychopsmossychops Posts: 262
    ste_ wrote:
    Thule aero bars and rack with 1 road bike on the roof knocks circa 5mpg off my X5.

    Am taking the bike to Southern France in August and have been considering a rear rack for just the reason of the increased economy.

    What worries me though is even a small tap from a car behind would write your bike off. :?

    I also like the roof mount - the bike is completely out of the way of the boot, plus it's what the pro teams use ain't it. 8) :D

    I do ok with my towbar mounted one, I am lucky with the Mondeo boot (is this the first time its considered lucky to have a Mondeo rather than an X5?). The Thule drops down so I can still access boot with the bikes on and if someone did tap the back, the floor of the rack would probably take the impact and transfer it to the towbar instead of my bike. Probably not much worse than keeping it in the boot. I can also see the bikes out of my rear view to make sure they are ok (my brothers bike fell off his Tauran, he still has the dent to prove it on the roof).
  • ste_ste_ Posts: 124
    I think the thing is to have a towbar mounted one as you suggest. That way the boot can be opened independently.

    Has given me food for thought anyway, cheers.
  • waddliewaddlie Posts: 542
    mossychops wrote:
    Thule Rideon in use here. I do an 180 mile trip to work and back every week, I am amazed that the rideon doesnt affect fuel consumption at all. I havent noticed any difference at all. I use a fuel logging app and can see no difference on here at all usually 37mph combined in a 1.8l Mondeo.

    Bike nor rack touches the car at all. Very stable. Takes the road bike and the full suss. Very impressed. Also has a light bar with number plate on it (obsuring your lights and number plate is illegal and I was a bit worried that with ANPR in use, this might become a favourite offence for traffic cops to "do you" for).

    2011-04-21%25252010.37.56.jpg

    Excellent rack that - the Thule 9502 to be precise. I got mine for about £90, although prices seem to have gone up since. There's a 3 bike version too (the 9503), easy to mount on the towbar, easy to get the bikes on and off and far more trustworthy than the webbing-and-slippy-clamps-on-the-bootlid nonsense.
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  • suzybsuzyb Posts: 3,449
    Looks like I may be in the market for a bike rack. The lever to unlock one of the back seats in my car seems to be broken so I can't drop the seat to get my bike in the car now :evil:
  • seatalteaseataltea Posts: 594
    Thule 9503 £10 from Halfords, yes that's right £10 new in a box 2yrs ago :D

    Has no impact on my estates mpg with three bikes on the back, have you never draughted a bus ? if not you'll never know the thrill of 40mph and no wind resistance.

    or the shock of hitting a bus at 40mph :shock:

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