How Do Bike Racks Affect Gas Mileage? [The Answer Will Surprise You]

Anyone who has ever watched a video of a vehicle in a wind tunnel can appreciate the degree of aerodynamic precision involved. Unfortunately, a single stand-out disrupts those clean curves of flowing air, destroying the visual effect, and that is using a bike rack to transport bicycles. So, how do bike racks affect gas mileage?

How Do Bike Racks Affect Gas Mileage?

Bike racks affect gas mileage by disrupting the vehicle’s shape, a shape designed and rigorously tested to achieve the maximum aerodynamic efficiency for that make and model. Anything that disrupts it slows it down and places the burden on the engine.

If enemies could be said to exist in this narrative, the biggest culprits are roof racks and the bicycles with bike racks that mount to them. 

However, that doesn’t mean that hitch and trunk-mounted bike racks are exempt from any fault.

What Kind Of Vehicles Aren’t Affected By Hitch And Trunk-Mounted Bike Racks?

Every vehicle is affected in one degree or another, but box-shaped vehicles fare the best. The Nissan Cube, Honda Element, or Kia Soul make good examples. When air passes over these vehicles, it experiences a far lesser degree of dropoff at the rear.

Watching vehicles go through the process of aerodynamic testing via wind tunnels is fascinating, and it tells you a lot about how a vehicle presses against the air at speed (or, in many cases, it could be described as more of a cut). 

The less the wind curves around the rear frame of the vehicle, the less it will counter any obstructions you have mounted back there, like a bike rack. Weight is another thing to consider, and it isn’t negligible.

A large, hitch-mounted platform bike rack that’s carrying four bikes can add almost three hundred pounds of weight that the engine has to pull. That might not seem too much when laid against a pull-behind camper, but weight distribution, sway, and wobble are also factors.

As far as roof racks with both a bike rack and bike(s) attached to it, there’s no getting around the detrimental effect of wind resistance and weight.

How Much Does A Bike Rack Affect MPG?

Roof-mounted bike racks can decrease fuel mileage by up to a whopping 35%. Even when there aren’t any bikes mounted to it, which is why you shouldn’t leave it on the vehicle when not in use. It has also been shown that the roof rack alone has a negative impact.

Hitch-mounted bike racks have been tested as well, and their effects were not positive. They weren’t as bad as the roof racks, but even an empty, hitch-mounted bike rack still had an impact. 

It stands to reason that a hitch-mounted bike rack and a trunk-mounted bike rack would have similar effects when carrying bikes. However, a trunk mount is probably negligible when empty. In addition, trunk bicycle mounts are very lightweight and easy to remove.

In July of 2013, Consumer Reports performed a test on a 2013 Honda Accord with a roof rack. The results were a 35% reduction in mpg (miles per gallon) with a two-bike, roof-mounted carrier installed on the Honda and traveling at 65mph. 

Without the bikes—just the roof rack and bike rack alone—the Honda Accord mpg was reduced by 5. When a wind deflector was added to the rack, it dropped by 7. 

Of course, the report’s conclusion couldn’t be more predictable. Remove your bike rack when not traveling, even if you’re traveling short distances, because mpg lost will add up over time.

Ultimately, the use of bike racks reduced 42 miles per gallon to 37 with a rack alone, 35 with wind deflectors, and 27mpg with bikes mounted.

How Different Bike Racks Affect Gas Mileage

It’s no secret that a roof rack will have far more impact than a hitch or trunk-mounted rack. However, Trunk and hitch bike racks also affect gas mileage.

In April of 2020, Consumer Reports conducted further testing on a 2019 Nissan Altima and a 2019 Toyota Rav4. The two vehicles couldn’t be more different in terms of shape and aerodynamic performance.

Nissan Altimas are sleek, sporty-type vehicles, while the Toyota Rav4 is a compact, sport-utility vehicle with a more boxy profile.

How Much Does A Bike Rack Affect Gas Mileage?

Both vehicles were tested at 65mph under a variety of conditions.

Nissan Altima And Toyota Rav4 With A Roof Bike Rack, With And Without Bikes

  • 2019 Nissan Altima with a roof rack and no bike: The Nissan experienced an 11% reduction in fuel economy with no bikes mounted to the roof rack.
  • 2019 Nissan Altima with a roof rack and two bikes: With two bikes mounted to the roof rack, the Nissan Altima experienced a 28% reduction in fuel economy.
  • 2019 Toyota Rav4 with a roof rack and no bike: The Toyota Rav4 experienced a 5% reduction in fuel economy with an empty roof rack.
  • 2019 Toyota Rav4 with a roof rack and two bikes: With two bikes mounted to the roof rack, the Toyota Rav4 experienced a 19% reduction in fuel economy.

Nissan Altima And Toyota Rav4 With A Hitch Bike Rack, With And Without Bikes

  • 2019 Nissan Altima with a hitch rack and no bike: The Nissan Altima had a minimal 3% loss in fuel economy with no bikes mounted to the hitch rack.
  • 2019 Nissan Altima with a hitch rack and two bikes: With two bikes mounted to the hitch rack, the numbers jumped dramatically to a 25% loss in fuel economy.
  • 2019 Toyota Rav4 with a hitch rack and no bike: Without a bike mounted to the hitch mount, the Toyota Rav4 experienced a nearly negligible 2% loss in fuel economy.
  • 2019 Toyota Rav4 with a hitch rack and no bike: Like the Altima, adding two bikes to the hitch mount caused the fuel economy loss in the Toyota Rav4 to jump to 12%.

How To Improve Fuel Efficiency With Bike Racks

The simplest answer is to remove it when you don’t need it. Sure, that could be a pain, especially for roof racks where it’s often a permanent modification.

However, you can at least remove the bike rack from the roof to minimize drag. Both studies were conducted at 65mph. That means that the loss of fuel efficiency will predominantly occur over the interstate, with long-distance travel. 

But even short distances add up over time. So if you don’t need the bike rack, remove it until such time that you need it. Unless, of course, you don’t mind the added fuel costs.

The Consumer Reports test did not include trunk-mount bike racks, but it’s easy to draw a conclusion based on the hitch-mount data. Trunk-mounted bike racks are the lightest of the bunch and probably don’t create much drag when empty.

That probably doesn’t apply when bikes are mounted to it. There will be some drag, and since trunk-mounts generally have a higher profile than hitch-mounts, there’s likely to be a drastic jump in fuel efficiency decline.

Final Thoughts

Bike racks have a detrimental effect on fuel efficiency, and that negative impact spans three different vehicles: A lighter, older model 2013 Honda Accord, a heavier, more recent model Nissan Altima, and a boxer compact sport utility in the Toyota Rav4. 

Those numbers are probably pretty elastic when considering larger SUVs and vehicles with a box-type of profile. However, what’s clear is that there is an impact, and the only real solution is to remove the bike rack when it isn’t necessary.

Battery-powered vehicles haven’t been tested in this regard either. However, physics is physics and doesn’t change regardless of what propels the vehicle forward.

A bike rack’s weight, distribution, and wind drag will affect the battery’s ability to work harder. Either way, while bike racks are great conveniences for transporting our bikes, they can also be a drag. 

With today’s high gas prices, you’ll save money by not having the bike rack on the back if it’s not being used!

Sources

Bartlett, J.S. (April 12, 2020). How Bike Racks Affect A Car’s Fuel Economy