Looks good; guzzles gas


Pricey aerodynamic drag/Richard Murphy

That fashionable roof rack on which you spent $600, $800, $1,000 or more to haul all your recreational toys around Alaska?

It’s destined to cost you a lot more than you ever guessed over its lifetime.

Researchers Alan Meier from the Lawrence Berkeley National Laboratory and Yuche Chen from the National Renewable Energy Laboratory put the racks to the test and discovered the increased drag they create could be costing drivers an average of 25 percent more in gas every time they drive.

The duo calculated drivers consumed about 100 million gallons of gas to haul their roof racks around the country in 2015, according to Scientific American. The costs are individually small but persistent.

On a car getting 30 miles to the gallon, an Alaska driver could expect to spend an extra $7 every time she drove to Kenai in July with a dipnet lashed to the roof rack. A trip to Fairbanks and back with a roof load of bikes would cost you somewhere in the neighborhood of $20 more at Interior gas prices.

Put 5,000 miles on the car over the course of the summer, and you could be out $125 or more. Figure you keep the car for five or six years, and the lost fuel might end up costing you as much as the rack did.

Specifically how big the MPG penalty for your vehicle depends, of course, on a variety of factors: what kind of gas mileage the vehicle gets to begin with, the type of rack and what is being hauled, and the weight of all the other stuff you’re hauling with you.

But the scientific findings by Meier and Chen back up less formal field testing done by Consumers Reports magazine three years ago.

Even bigger fuel losses in reality?

“As we cruised at 65 mph in (a Honda) Accord with a pair of bicycles on a roof rack plus wind deflector, our highway fuel economy plummeted by more than a third, from a miserly 42 mpg to a miserable 27 mpg,” CU reported. “The rack alone wasted 5 mpg.”

Mileages for CU’s Accord fell from 37 with the rack alone to 35 with a wind deflector which is supposedly designed to improve mileage to 27 with the deflector and two bikes. CU did not test big drag items like roof-top boxes or boats.

Roof racks are everywhere in Alaska, hauling bikes, kayaks, snowboards, skis, dipnets, coolers and miscellaneous outdoor gear. All of that gear messes up aerodynamics, especially on modern automobiles optimized to squeeze the most out of every gallon of gas by minimizing drag.

The CU observations would indicate that if you plan to haul a lot of Alaska gear you might want to think about just getting a truck. A 2016 Ford F-150 pickup gets 26 mpg on the highway, according to the federal government. That’s only one mile per gallon less than the CU Accord with two bikes on the roof.

And a 2009 aerodynamics study conducted by Feysal Adem, a graduate student at the University of California, Sacramento, concluded that a pickup with a properly designed canopy over the bed got even better gas mileage.

All of which would suggest that if you’re hauling a lot of Alaska toys, a pickup might make more sense than a compact or mid-size car with a roof rack. Or you could, as suggests, ditch the roof rack in favor of a hitch rack.

“Hitch mounted bike (racks) can be expensive to install and require drilling into your vehicle’s frame, but don’t create as much wind resistance as their roof mounted counterparts,” mountain biker Saris Mercanti writes there.

Costly and difficult installation may or may not be true in the case of your car. Simple, bolt-on racks are now available for many vehicles.

There are trade-offs in all cases. A pickup truck with canopy used to commute to work all week long is going to cost you more in fuel over the course of a year than CU’s Accord topped with a roof rack no matter how well the vehicles match up on weekends.

Even with a daily 5 percent mileage loss due to an empty rack, the Accord gets significantly better gas mileage than any truck. And an Accord outfitted with a hitch rack instead of a roof rack makes rack removal incredibly simple: Pull a pin, remove the rack, and you’ve restored the original aerodynamics of the car.

It’s all trade-offs

Not only that, the hitch rack is easier to load than the roof rack. On the other hand, as with the roof rack, it offers your bikes no protection from the rain and it lacks for versatility. You can’t haul a kayak on a hitch rack.

But an 8-foot, sit-on-top kayak will fit under the canopy of a pickup with a standard, 8-foot bed and a canopy ensures you arrive at your weekend destination with dry boats, bikes and other gear.

Plus, if you’re going camping and forced to stay in one of those Alaska or Yukon Territory campgrounds where marauding bears have limited campers to “hard-sided vehicles only,” you can throw the gear on the roof of the vehicle for the night and have a place to sleep.

Equipment on the roof of a parked vehicle has no effect on mileage.







2 replies »

  1. I don’t see the data for a rack that holds the bike across above the rear bumper. In that position would seem to act more like an aerodynamic spoiler and might not be such a drag.

  2. Another reason truck canopies are better than roof or hitch racks is security. With racks, people (especially bad people) can immediately see that you have a $4000 bike that is asking to be stolen. The bike is out of sight and out of (criminal) mind if it is inside a canopy. Security is usually better with a truck canopy. You can lock the bike to the truck bed and then lock the canopy. Cables and chains on racks fall too easily to bolt and cable cutters. Plus, expensive components can be stolen. Canopies also keep your expensive toys clean. Roof and hitch racks do not.

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