Hardtop carrier roof positioning

[bubbatime]

I'm going on a 1600 mile road trip. Just mounted a hardtop rooftop cargo carrier on the vehicle (2009 Chrysler Town & Country). The roof rack adjustments are so that I can push the rack up near the front of the car, in the middle of the car, or 3-4 feet back near the rear of the car.

Anyone have experience with this stuff? Wondering if any wind or strange harmonics might occur in any of the various positions that I am able to mount it on the roof. My gut says to mount it in the middle, but it is much easier to load mounted near the front and may offer better wind resistance all the way back as the air coming over the windshield might effect it.

Similiar to this model:

 

[Brybo86]

i would try and have the line of the windshield match the angle/line of the roof carrier..?

 

[RoadRaceJosh]

Mount it toward the front with the blunt end forward. Go to ecomodder.com and look at the aero template to see why/how. http://ecomodder.com/forum/tool-aero-template.php

 

[OneEyeJack]

You can experiment with corn starch. Spread a fine layer on top and drive at your expected cruising speed. Do this with the carrier in different positions until you get the least amount of corn starch left on top. Corn starch left means the air flow has separated which equals more drag.

You can also use this method to place vortex generators near the rear of your carrier. Just place them a few inches forward of the line that indicated air separation near the back of the carrier. The vortex generators should be about 2x2 inches and mounted vertically at an angle to the air flow. The ones in the center should be almost straight ahead and the ones toward the sides of the carrier should gradually transition to about a 30 degree angle to the air flow.

 

[IndyIan]

Originally Posted By: Joshua_Skinner
Mount it toward the front with the blunt end forward. Go to ecomodder.com and look at the aero template to see why/how. http://ecomodder.com/forum/tool-aero-template.php

+1 Although you'll probably have to endure a few comments pointing out that its backwards...

 

[Hokiefyd]

Depending on the load, mounting it further forward will also help with weight distribution. If your '09 is anything like our '07 was, rear suspension damping was not a strong suit, and it really got woolly if it was loaded with a lot of stuff in the back.

 

[Astro14]

If you've got a sunroof and plan to open it, then as far aft as possible will reduce buffeting and airflow interference.

Otherwise, I'm with you on putting it forward to reduce the aft loading on the suspension.

Further, try to keep the weight out of it. Heavy suitcases in the van near the floor, things like pillows, sleeping bags, that are bulky but light in the carrier to minimize the adverse handling that will result from a higher CG.

I've got one of these: http://www.yakima.com/shop/cargo/cargo-boxes/skyboxpro16

Although it's aerodynamic, it still adds drag. On the Volvo wagons, it's nearly as long as the roof, and creates the buffeting around the sunroof. On the 4 Runner, it simply lessens the already anemic V-6 on the highway with the added drag. In either vehicle, I lose about 2 MPG.

 

[rjundi]

Completely vehicle dependant in my findings as aerodynamics differ in terms of noise/turburlence.

 

[hpb]

Interesting question, and one that is relevant to me as we're going on a 2 week road trip in January, with a roof pod (as they're known here) on our CX9. My roofracks have some scope for adjustment too and I've been pondering which position would be best for them. Let us know what ends up working for you. And, fuel savings or not, I won't be mounting the pod "backwards", my OCD just wouldn't allow that!