Pick up truck tailgates

[luvtheus]

Can anyone tell me if driving with the tailgate down on my truck help or hurt fuel mileage? I have a 2002 Chevy Silverado 6.5 ft bed with aluminum toolbox in the back mounted directly behind the rear window. I have heard yes and no answers about this in the past but have never seen anything done on it like a study or anything official yet. If anybody here can help me answer this question, thank you in advance, John......

[Frank Lee]

Search function up above; many questions of this nature have been extensively discussed. If you want details and such search it; the short answer is leave the gate up.

[yugomodder]

Hi luvtheus,

Here is some good information about pick up truck aerodynamics. It's a study done by Feysal Ahmed Adem at California State University.
http://csus-dspace.calstate.edu/xmlu...pdf?sequence=1
The most useful information is at the bottom of the report. There is a good picture showing flow with the tailgate up and how the air interacts with the bed, tailgate, etc. There are lots of good diagrams in that report. I'll have to thank the guy who first posted it to ecomodder.

And just as Frank Lee said short answer, up is better than down.

[SvdM]

[Frank Lee]

Pic show partial cover giving somewhat less improvement than full cover, yet in one of aerohead's recent posts he lists partial cover as being waaaaay more effective than full cover. I think aerohead suffered a typo...

[luvtheus]

Thank you all for the reply. I feel stupid for thinking the tailgate down was better for airflow but I cannot dispute an official study. Today my tailgate goes back up. I even tried driving around with it off the truck. It is near time to take a second mortgage on my house and fill the tank up on the ole Silverado so will do another mpg check at the end of the next tank full. Should be interesting. Thanks again for the help gentlemen, John. Dont know what gas prices are in other parts of the country but here in middle Tenn it is $3.59 per gal on average. When is our "government" going to get wise?

[SvdM]

@ luvtheus - don't worry, I also came here with the idea that down is better than up. You guys should be thankful. If my calculations are correct, the $ price equivalent is soon going to be $5.40 per gallon here in South Africa.

[Sven7]

edit: apparently that was already posted... see above picture

[aerohead]

Originally Posted by Frank Lee

Pic show partial cover giving somewhat less improvement than full cover, yet in one of aerohead's recent posts he lists partial cover as being waaaaay more effective than full cover. I think aerohead suffered a typo...

I don't have my work book with me so I don't have specific numbers.
GM's patent for the 1/2-tonneau was based on a C-10 pickup before the
'all-new' truck debuted.
In their US Patent they have a performance graph of the cover,as a function of percent coverage of the bed,as measured from the back.
The 1/2-tonneau did have lower drag than the full cover.
Texas Tech based their research on an F-150 short and long bed,both in model and full-scale.And its clear that their data reflect no advantage to the full cover.
When Sport Truck Magazine did a cover story on pickup aero,they had quotes from reps from each of the Big-Three auto/truck makers.From the reading you are led to believe that each pickup must be taken on a case-specific basis.
Consensus was that
'gate-up' was best,although at least one rep reported that if the gate could be hinged at the top,then their truck would show a better number.
It's not gonna be a one-size-fits-all situation.
Short of having access to a wind tunnel I'd be comfortable with going with the gate up,1/2 tonneau combo.
It worked on the pre-T-100 Toyota pickup,1990s Ford 4X4,late 80s Chevy 1/2-ton,T-100,'62 Dodge D-100,1st-gen Tundra.These I know of 1st hand.

[Frank Lee]

OK, thanks.