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Old 11-27-2009, 11:40 PM   #1 (permalink)
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Question Car Top Carrier Question

I just registered with ecomodder, and I wanted to ask some of you experts a question about car top carriers.

I have a Toyota Sienna, 2004 that I fill up with six kids and two adults. This summer, we plan to drive from Nova Scotia to British Columbia to see my wife's parents. We will be going about 15,000 kms (9,000 miles) in total.

With all those people, we need a car top carrier. We currently have one of the hard shell type-- rather boxy but rounded with a bit of taper to it-- the kind you can get at sears. It is 18" tall and 36" wide and 48" long. I have considered getting a shorter, narrower, longer style to decrease wind drag, but I have no idea how much difference it would make.

Would any of you be able to give me some idea of how much difference it might make in my gas mileage? I don't need to know exactly, just a rough idea.

With the van all loaded up (so much weight that it rides low) on previous trips with the car top carrier in place, we have averaged between 26 and 27 mpg (which interestingly is the same mileage we get driving around town without the carrier or a load). I ordinarily drive about 5 mph over the speed limit with cruise on which often means 70-75 mph. I do look ahead and coast when I can.

I would really appreciate any help you could give us. Finances are tight with such a large family, so every bit helps.

Thanks so much.


Last edited by CROSS CANADA WITH 8; 11-28-2009 at 09:04 AM..
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Old 11-28-2009, 12:23 AM   #2 (permalink)
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Old 11-28-2009, 12:44 AM   #3 (permalink)
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The cost of a new cargo carrier will buy a lot of gas
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Old 11-28-2009, 01:43 AM   #4 (permalink)
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A longer and narrower cargo carrier would probably be more efficient, but not enough to validate the cost of buying a new one when you already have one that isn't damaged.

If the one you have now ends up breaking or is damaged or something and you need to buy a new one, I would say it would be worth a little extra to get a long narrow one (assuming they might be more expensive?) but not at this point.
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Old 11-28-2009, 03:10 AM   #5 (permalink)
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To anyone out there that wants an off the shelf "cargo expander" buy one like the above.


To the OP, picture of the cargo holder?
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Old 11-28-2009, 03:32 AM   #6 (permalink)
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The cargo rooftop carriers that you get from sears, you should probably mount it backwards, right at the end of your vehicle. It might hurt a little less that way, by helping to train the flow down over the rear hatch of your van.

But, probably not. You'd almost be best off trying to take everyone's crap and making a boat tail out of it on the back window of the van, honestly. Might get a gain out of it!
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Old 11-28-2009, 05:01 AM   #7 (permalink)
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15,000 miles? How many times are you going to drive there? It's only like 3000 to 4000 miles between the two. Heck, the earth is only 23,000 miles around at the equator. If you want to save gas, recalculate your route.
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Old 11-28-2009, 05:19 AM   #8 (permalink)
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Old 11-28-2009, 06:33 AM   #9 (permalink)
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Basically you want to go fast with a big draggy box on your roof. IMHO you've created a worse case scenario for FE. You're going to take a hit no matter what car-top carrier you choose.

As far as FE goes weight is a dominant factor in stop and go city driving, while high speed cruising is mostly about clean aerodynamics and restraint on the go pedal. Hopefully you can quickly detach the carrier off the vehicle when it's not needed.

As a personal object lesson, I had a VW diesel a few years ago and used a ski rack for obvious reasons. At 70 MPH it knocked almost 25% of my FE, so it stayed off the vehicle until needed. Live and learn.
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Old 11-28-2009, 07:29 AM   #10 (permalink)
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About the detaching ability--yes, I have it rigged so I can take it off very quickly.

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