Want To Boost Gas Mileage? Remove That Bike Rack, Says Consumer Reports

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Bicycle racks can affect aerodynamics (Image: Flickr user kardboard604)

Bicycle racks can affect aerodynamics (Image: Flickr user kardboard604)

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If you're one of the millions of Americans preparing for your summer vacation, you might also be readying the family's bicycles for some exercise while you're away.

Chances are, this involves some kind of roof-mounted bicycle rack for your car. And this can have a dramatic effect on your gas mileage.

Consumer Reports has calculated just how much extra gas the aerodynamic hindrance of a bike rack can cause, recording figures with a 2013 Honda Accord LX.

The 2.4-liter four-cylinder vehicle, capable of 29 mpg combined with an auto transmission and 28 mpg combined with the manual, achieves 30 mpg in CR's own testing.

Better still, at a steady 65 mph it recorded a test baseline of 42 mpg--against which the effects of a bike rack can be measured.

The differences are surprising. With a rack alone, that 42 mpg Accord drops a full 5 mpg, down to 37 mpg at 65 mph. With a wind deflector--for the bikes, rather than to reduce the drag of the rack, that drops further to 35 mpg.

Worst of all, a rack with two bikes and a deflector returns just 27 mpg at 65 mph, a 15 mpg or 35 percent drop compared to the bike-free vehicle. Throw in the weight of a family and all their luggage, and you'll see that figure tumble further.

These figures will vary depending on your cruising speed. A trip across town, with lower speeds and a shorter journey time, may not impact your finances much, but a 15 mpg drop (or more) over several hundred miles will start to cost you. You can mitigate this to some extent--dropping your speed, or driving more gently--but the bottom line is that anything external to the vehicle will really ruin those finely-honed aerodynamics.

Obviously, there's little alternative if you want to take your bikes away on vacation--short of occupying space in the car itself, they'll either be going on the roof or attached to the back of the car. And at least using the bikes once you arrive is a green (and healthy) means of getting around.

But once that vacation is over, remember to remove your bike rack--otherwise you'll be paying for that vacation for the rest of the year.


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Comments (14)
  1. I said it before, there's nothing wrong with a fold-up bike. I'd imagine a few could fit in a Rooftop Cargo Carrier.

  2. In other news, the water in the atmosphere filters out all colors more than it does blue, making it appear to be blue.

  3. Very droll, Mittar. The news here was just *how much* such a thing affects gas mileage...

  4. Sorry, I must've been in a droll mood lol.

  5. What is good about the Consumer Reports article is that they quantified the MPG loss. I see so often empty bike carriers and the driver doesn't have a clue the mileage loss (s)he is experiencing. (Or the driver would have taken the five minutes to remove the carrier.)

    Now we can mention to the clueless driver just how inefficient it is to drive with the empty rack.

  6. I suspect that people who use their bike rack a lot (to get to local bike trails or state parks) aren't going to be taking them on and off all the time. They'll live with the lower gas mileage.

  7. What is the difference with bike rack mounted on roof verses on back bumper?

  8. Hitch-mounted rack on my car. I see less than 1 MPG drop in fuel economy with the rack and bike on my car. These have less aerodynamic drag than roof racks because they sit behind the car and stay mostly out of the slipstream.

    My hitch-mounted rack is far easier to put on or take off than a roof rack as well.

  9. I have a 2012 Subaru Outback that I recently drove from Houston to San Diego, mostly at 75 - 80 mph. Highway mileage rating is 25 mpg. With the roof rack and 2 bikes on top, we got 20 mpg, a drop of 20% (not quite as bad as the 35% drop this article states).

  10. Easy solution!

  11. Just take a visit to CA and see how many ski/snowboard racks are still left on the roof of SUVs months after skiing season...

  12. Surely those are left there just so everyone can see that they're a skiier/snowboarder... sacrificing a few em-pee-gees for the cool factor ;)

  13. I guess.

    I thought leaving the SUV full of mud is actually cooler than being a ski bum... :)

  14. But what type of bikes did they use? Were they mountain bikes? Beach cruisers? Road? I'm sure that a full blown tri-bike wouldn't have had such a dramatic effect.

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