I'm surprised that no one has mentioned the article in this month's issue of Road & Track regarding the aerodynamics of tailgate up or down. Most folks on this well informed site probably have an opinion for that topic, but this is the first time I have seen the results of actual testing. The article is in the R&T Tech Tidbits section and with some humor they admit that trucks aren't their forte, but acknowledge that there are many on the road so they felt this would be of interest.

They describe the testing done by National Research Council of Canada in which they performed both wind tunnel testing on trucks and computer analysis of truck shapes. Both indicated a minor increase in drag and rear-end lift with tailgates down or removed. Mesh tailgates also showed the same increases. Only one truck, a 2001 F-150 showed a very slight improvement with the tailgate down. A truck tested with tonneau covers showed an improvement over having just the tailgate up.

So, next time you are at the track and looking for every bit of advantage, keep the tailgate up.

 

I had read about this somewhere on this board. I think it is hilarious. You see so many people running around with them down. Physics is a funny thing.

 

i think most people know that info. not sure where i learned it from but i have always known it. up is better than down. now the better question is leave it on or take it off. i think for the 2wd it might be better to just leave it on but for the 4wd the increase in drag is more than offset by the loss of ~50lb's. dont really know that for sure though.

 

Both indicated a minor increase in drag and rear-end lift with tailgates down or removed.
So, next time you are at the track and looking for every bit of advantage, keep the tailgate up.[/QUOTE]

Is it just me or does that not make sense?

 

i think whats going on is there forms a high pressure area in your bed and the air just flows over it. instead of having massive turbulance behind the cab of your truck in the bed, you have some behind the cab and some behind the tailgate. I dunno, physics is cool though!

 

i was told with it up there is a bubble of stationary air in the box that acts like part of the truck and the air just floats right over it. with it down the air makes a sharp drop after the cab and does become turbulent.

 

It makes sense to me. They are saying that both conditions, tailgate down or removed, create more drag than tailgate up. The actual Cd figures given for a test truck, 2002 Ford F-150 Crew Cab were:

Tailgate up: 0.5304
Tailgate down: 0.5425
Tailgate removed: 0.5596

A partial tonneau cover: 0.5072
Full tonneau cover: 0.4967

All are about the same as a brick, but brick races don't get much press coverage.

 

Ok, I misunderstood.....weird though

 

That is weird! So on my ECSB Sportside it would be better to leave my tailgate and my 100+lb tonneau cover on? When I ran a 14.99 it was with no gate or tonn cover!

 

I have been having serious debates in my head about this.

I usually run without the tonnue and no tailgate due to the crazy amount of weight you save like Parish said. My tailgate is 45lbs on my scale and the bed cover has to be at least 120+lbs. I have a Snug Top full cover and it is too heavy and akward to lift alone.

I guess all I can do is try to make runs both ways and check DA a few times both ways and see if I can see a clear advantage.