Roof rack test: quantifying the aero penalty

[Cd]

Ya think these guys noticed any change in MPG and wind noise ?

[lucidexp]

Originally Posted by mikel09

The wrath of roof rack and roofboxes has been independently tested by Edmonds and Consumer Reports. The impact was 17-25% depending on car, speed type of carrier. I have been developing an idea based on shortened boat tail plates tested on semi trailers, integrated in a cargo carrier for suvs, wagons, hatch backs, and sedans.

Essentially a back mounted aerodynamic cargo carrier. It eliminates the ~20% mpg penalty of roof top carriers and has improved mpg 5-10%, in preliminary tests with the boat tail design. We use it for camping, family road trips, ski equipment etc. AeroPACKusa is the product. I would appreciate your comments. Thanks!

I like it. If you ever make anything like that for a surfboard let me know.

Also just brainstorming if you created a quickly removable, easily secured tie-down system and sold it fairly cheap you could make a killing here in Southern California targeting the surfing industry. The current selection of 'inexpensive' racks is not that great at all.

[MetroMPG]

lucidexp: you might be on to something. I remember another EM member way back when who signed up specifically to noodle about a better way to deal with his surfboard roof rack.

Also: I missed it when Mikel09 originally posted, but I think he might have contacted me first to ask if he could mention his product on the forum. (And I said, "sure.")

[lucidexp]

Originally Posted by MetroMPG

lucidexp: you might be on to something. I remember another EM member way back when who signed up specifically to noodle about a better way to deal with his surfboard roof rack.

Also: I missed it when Mikel09 originally posted, but I think he might have contacted me first to ask if he could mention his product on the forum. (And I said, "sure.")

Being a fellow surfer and having my truck die on me I have had to resort to having a car, but dont want to give up surfing because of it.

I have looked around and tried a few but several current version of removable racks are really, really bad. I have seen some flatable roof racks but they sell for around $100 and for that you are better off getting a 'real' rack.

I have the design tools and a degree in architecture, willing to give the design away since I just want a solution.

[mikel09]

Guys this sounds interesting. Are you thinking about a roof mount or back mount surfboard carrier? What are your thoughts on the concept?

Originally Posted by lucidexp

Being a fellow surfer and having my truck die on me I have had to resort to having a car, but dont want to give up surfing because of it.

I have looked around and tried a few but several current version of removable racks are really, really bad. I have seen some flatable roof racks but they sell for around $100 and for that you are better off getting a 'real' rack.

I have the design tools and a degree in architecture, willing to give the design away since I just want a solution.

[MetroMPG]

Originally Posted by lucidexp

I have the design tools and a degree in architecture, willing to give the design away since I just want a solution.

New thread! (Please, if you're going to do it.)

[aktacoma]

i know this is an old thread but im wondering would it make any difference if i make a roof rack and mounted it on an aero cap?? would that be worse that just keeping my truck cap and putting the bike inside?

[JRMichler]

My brother has an F250 with an aero topper. It's described here: http://ecomodder.com/forum/showthrea...250-16798.html

Since then, he added four eyebolts to the topper for tying down a 13 foot canoe. The canoe lays upside down on the topper with one end over the cab and the other end sticking out back a little bit. He has not noticed a mileage decrease with that setup, so any mileage hit is less than 1 MPG.

I think his success is due to the canoe being down tight against the topper.

[MetroMPG]

Updating this 11 year-old thread...


Consumer Reports asked:
What's the Impact of Carrying Stuff on the Roof?

They tested with a  2013 Honda  Accord at 65 mph / 105 km/h.

• 42 mpg US - baseline with nothing on the roof
• 37 mpg - empty bike rack
• 35 mpg - empty bike rack with wind deflector (made it quieter, but increased drag)
• 27 mpg - two bikes on the rack (didn't specify deflector or not)

They also tested a 2008 Camry with a large car-top carrier...

• fuel economy dropped by 5 mpg

Source: https://www.consumerreports.org/fuel...l-economy-now/


Moral of the story: carry stuff inside the car or on the back whenever possible!

[samwichse]

I put a pair of Kayaks on my Civic hybrid to drive to the lake near my dad's house. I made ~48mpg getting to his house (11.5 hour drive). Going from his house to the lake and back (1.5 hours) with the Kayaks on, the drag was so great I had to use 4th gear to maintain 60mph on the backroads without flattening my hybrid battery... I made about 35 mpg.

Huge difference. Note: I had an aero-clean car (no rack) for the drive to his place, the Kayaks were put on one of those gutter strap-down roof racks he had at his place.