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Open Roads Forum  >  Travel Trailers  >  Modifications and Accessories

 > INcreasing mileage with a cap

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sperduton

Lebanon Township, NJ

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Posted: 07/06/08 08:43pm Link  |  Quote  |  Print  |  Notify Moderator

I currently tow a 34 foot trailer with a 2004 Ram quad cab long bed.
I'm in the process of planning a long trip that will take me about 5000 miles.
Usually I run with an open bed. But I have an opportunity to borrow a cap (not a tonneau cover) for the bed for the trip. I'm wondering if I would see an increase in mileage while towing if I were running a cap.

Anyone have any experiences ?

Thanks,
Nick


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DutchmenSport

Indiana

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Posted: 07/06/08 08:48pm Link  |  Quote  |  Print  |  Notify Moderator

Use the cap. For the advantage of having the bed of your truck dry, and all the items in it dry, and no danger of anything blowing out, and being able to secure items "a little better" against theft, is worth it, regardless if it provides better gas mileage or not.

However, I think the cap helps a lot. I've towed only a short time without a cap. I like the cap on much more than off. Also, with the canoe, it's just plain "sweet!" (Hard to explain, but it is).


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newsomer

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Posted: 07/06/08 08:49pm Link  |  Quote  |  Print  |  Notify Moderator

I've seen a very good study that focused mostly on the myth that running with the tailgate down will increase MPG. They debunked that idea and showed that it even had the tendency to increase fuel consumption. They also said that running with a cap or tonneau cover was a wash on short and medium beds but could even be a detriment on long beds. They did no studies that included towing a wind dam like we drag behind the TV. I suspect that for the same reasons, aerodynamic design, that the cap would not make much difference when towing.

I don't remember where the study was published but I'll search and if I can find it I'll post the link later.


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grantster

Beautiful British Columbia, Canada

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Posted: 07/06/08 09:07pm Link  |  Quote  |  Print  |  Notify Moderator

I love our cap, but not for any gas savings (there isn't).

tom_kat

way upstate new york/lake george area

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Posted: 07/06/08 09:08pm Link  |  Quote  |  Print  |  Notify Moderator

myth busters did it on there show but no cap or trailer towing.just the tail gate up got better mileage with out towing.


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skipnchar

Topeka Kansas USA

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Posted: 07/06/08 09:16pm Link  |  Quote  |  Print  |  Notify Moderator

newsomer wrote:

I've seen a very good study that focused mostly on the myth that running with the tailgate down will increase MPG. They debunked that idea and showed that it even had the tendency to increase fuel consumption.

The test did not include ANYTHING about towing. It was done when running just the truck. I'd be very surprised if you didn't see a SLIGHT fuel mileage increase using the cap. It will be small because drag will be increased by the cap but wind resistance on the trailer will be decreased. You should gain slightly more when towing than you loose when running without the trailer.


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JJBIRISH

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Posted: 07/06/08 09:18pm Link  |  Quote  |  Print  |  Notify Moderator

I doubt you will see any increase and maybe a unmeasureable decrease due to the added weight...

but I would much prefer the cap for all the reasons most people buy them for...
protecting the load from wind and rain...

my old S/10 showed a remarkable drag with a cap that was just a few inches higher than the roof... of coarse there wasn't a big brick being towed behind it either...


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4campnuts

Southern NH

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Posted: 07/07/08 05:16am Link  |  Quote  |  Print  |  Notify Moderator

Can't hurt, can it? And , you gain extra dry space for your trip.

Sportsman2505qss

Winter Springs, Fl USA

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Posted: 07/07/08 05:31am Link  |  Quote  |  Print  |  Notify Moderator

WE had a cap on our old truck and it was heavy. I would think that would bring down the gas mileage a bit. We have a tonneau cover on this truck. I would say like everyone else, it's nice to have your stuff covered.


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VintageRacer

Dundas, Ontario

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Posted: 07/07/08 05:46am Link  |  Quote  |  Print  |  Notify Moderator

The reason a cap increases drag is the larger square, sharp cut-off at the back of the vehicle - an awful lot of drag is caused by the shape of the rear edge of the vehicle. When towing - you're in tandem with that big trailer and the back of the truck no longer matters. What matters more is shaping the airflow to the front of the trailer, and a cap does help with that. You should see better gas mileage and you should see less sway. My own experience (sadly in the opposite direction - losing the cap and getting increase sway and worse mileage) confirms that.

Brian


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