Tailgate down = better MPG?
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Yeah, CVT is around now - it's available somewhere, can't remember.
Thing is, if built right, it will hold together better than the first AOD's, E40D's, etc. etc.
I think for the tailgate down reluctance on the part of the manufacturer, they don't want the liability attached with losing a tailgate because they said the MPG would be better with it down (or contents of bed, etc)...
Thing is, if built right, it will hold together better than the first AOD's, E40D's, etc. etc.
I think for the tailgate down reluctance on the part of the manufacturer, they don't want the liability attached with losing a tailgate because they said the MPG would be better with it down (or contents of bed, etc)...
Laughing Gas
Joined: Jun 2003
Posts: 1,166
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From: Chino, California
I think for the tailgate down reluctance on the part of the manufacturer, they don't want the liability attached with losing a tailgate because they said the MPG would be better with it down (or contents of bed, etc)...
Oh, brother!! Everything has to have an alterior motive. Couldn't it be because it's the truth.... maybe? I doubt Ford is worried about their liability.
Oh, brother!! Everything has to have an alterior motive. Couldn't it be because it's the truth.... maybe? I doubt Ford is worried about their liability.
Posting Guru
Joined: Mar 2002
Posts: 2,245
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From: Vancouver Wash USA
Originally Posted by krewat
Yeah, CVT is around now - it's available somewhere, can't remember.
Thing is, if built right, it will hold together better than the first AOD's, E40D's, etc. etc.
I think for the tailgate down reluctance on the part of the manufacturer, they don't want the liability attached with losing a tailgate because they said the MPG would be better with it down (or contents of bed, etc)...
Thing is, if built right, it will hold together better than the first AOD's, E40D's, etc. etc.
I think for the tailgate down reluctance on the part of the manufacturer, they don't want the liability attached with losing a tailgate because they said the MPG would be better with it down (or contents of bed, etc)...
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Originally Posted by pops_91710
Oh, brother!! Everything has to have an alterior motive. Couldn't it be because it's the truth.... maybe? I doubt Ford is worried about their liability.
And, actually, I was saying that with some sarcasm, I wasn't being serious
Why do drug companies make these really nice commercials and then list every side-effect? Because if they don't someone will sue them because they didn't say it caused heart-attacks. It's all about liability...
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
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From: Long Island USA
Originally Posted by captainsstable
closed gate creates high pressure (similar to top of an airplane wing) thereby creating lift (reducing weight)
does lighter vehicle get better fuel economy?
does lighter vehicle get better fuel economy?
Even if the tailgate produces a "high-pressure area in the bed", that extra drag is going to bring DOWN mpg. There's no getting around entropy (loss/friction).
It's obvious to me, with a cap on the bed, and without, there is a 1-2MPG difference with my '01 V10 SuperCab ShortBed. I've done it 7-8 times for over 250 miles one way, and each and every time, I see 13.5-14MPG without the cap, 15-16MPG with (as long as I don't exceed 75MPH on level ground too much).
I have never tried running without the tailgate... however, I'm going to theorize a little and say that without the tailgate, you'll still have a LOT of turbulence behind the cab and in the bed, and you wouldn't see as much of an MPG improvement as a cab-height cap would give.
I have an ARE cap, it's one of the models that is more aero-dynamic, so there might be an advantage to what kind of cap you have too...
Cargo Master
Joined: Jun 2003
Posts: 2,203
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From: Carlsbad, California
My dad called the CVT the Salsbary (sp?) drive after some motor scooter that had it when he was a kid back in the '40s or there abouts.
Our snowmobile had one in it back in the early '70s. I must say that it was kind of neat watching it work and for performance it seemed to work well too. They used a rubber belt that ran on two pulleys, one which contracted and the other which expanded - net effect was a continuous change of ratios like a smooth version changing front and rear sprockets on a bicycle.
The problem was that as the drive belt wore down in width you lost top end because it would no longer climb the front pulley as high.
Our snowmobile had one in it back in the early '70s. I must say that it was kind of neat watching it work and for performance it seemed to work well too. They used a rubber belt that ran on two pulleys, one which contracted and the other which expanded - net effect was a continuous change of ratios like a smooth version changing front and rear sprockets on a bicycle.
The problem was that as the drive belt wore down in width you lost top end because it would no longer climb the front pulley as high.
Logistics Pro
Joined: Jan 2002
Posts: 3,733
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Tail gate down or up does not make any mpg difference on my last two superduty trucks. Both got/get 1-3mpg increase with a coverd bed. One with cover and one with a cab height cap. Got a buddy with same truck and a Higher than cab height cap. It cost him 1mpg he says.
Daryl Hunter our 70s SkiDoo only one pully that did the in out dance. Would have been cool to have both do it. And yes they ate belts very fast. Royal PITA to change too.
Daryl Hunter our 70s SkiDoo only one pully that did the in out dance. Would have been cool to have both do it. And yes they ate belts very fast. Royal PITA to change too.
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Posting Guru
Joined: Mar 2002
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From: Vancouver Wash USA
Originally Posted by Daryl Hunter
My dad called the CVT the Salsbary (sp?) drive after some motor scooter that had it when he was a kid back in the '40s or there abouts.
Our snowmobile had one in it back in the early '70s. I must say that it was kind of neat watching it work and for performance it seemed to work well too. They used a rubber belt that ran on two pulleys, one which contracted and the other which expanded - net effect was a continuous change of ratios like a smooth version changing front and rear sprockets on a bicycle.
The problem was that as the drive belt wore down in width you lost top end because it would no longer climb the front pulley as high.
Our snowmobile had one in it back in the early '70s. I must say that it was kind of neat watching it work and for performance it seemed to work well too. They used a rubber belt that ran on two pulleys, one which contracted and the other which expanded - net effect was a continuous change of ratios like a smooth version changing front and rear sprockets on a bicycle.
The problem was that as the drive belt wore down in width you lost top end because it would no longer climb the front pulley as high.
Cargo Master
Joined: Jun 2003
Posts: 2,203
Likes: 0
From: Carlsbad, California
Now that you mention it, it probably was only the one pulley that moved. It was the front one off the crank and would squeeze in as the revs increased. As the belt wore it wouldn't ride as high on the pulley and you lost some of the top end ratio.
The other problem that I remember with it was that the nut that held the assembly together was always wanting to loosen up. So my dad put some Locktite on it. Unfortunately he used the stud setting grade versus the normal blue colored liquid. When the time came to change the belt there was no way that we could get it off without an impact wrench
The other problem that I remember with it was that the nut that held the assembly together was always wanting to loosen up. So my dad put some Locktite on it. Unfortunately he used the stud setting grade versus the normal blue colored liquid. When the time came to change the belt there was no way that we could get it off without an impact wrench
Logistics Pro
Joined: Jan 2002
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Sorry for the hijack FYRETEK
Daryl Hunter keeps dragging me back memory lane.
Too funny, my dad did the exact same thing and the next time we did a belt change I had to hold the propane torch while he beat the end of a breaker bar with a hammer (no impact wrench for my Dad, that would be cheatin!)
Oh yea leave your gate up and drive like the wind SuperDuty Gas trucks love to run! In 5 years I have not seen one single majic mpg adder except air in the tires!
Daryl Hunter keeps dragging me back memory lane.
Too funny, my dad did the exact same thing and the next time we did a belt change I had to hold the propane torch while he beat the end of a breaker bar with a hammer (no impact wrench for my Dad, that would be cheatin!)
Oh yea leave your gate up and drive like the wind SuperDuty Gas trucks love to run! In 5 years I have not seen one single majic mpg adder except air in the tires!
New User
Joined: Jan 2005
Posts: 23
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There are two factors at play here, and the answer depends on which
factor outweighs the other.
The first is the added weight that having the tailgate down puts
on the rear tires. More weight means better road contact.
The second is wind resistance. You might think that having the gate
up creates resistance. And it does until a certain point, at which time
a pressurized pocket of air is formed in the closed bed. The outside
air flows more smoothly *over* this pocket than it does flowing over
the cab bed (as it would if the gate were left down or off).
So, whether the benefit of the added weight distribution gained by
having the gate down outweighs the benefit of having the air pocket
when it is up is the question, and this can only be borne out by
experimental testing. That is, drive each way and check your milage.
I believe it has been published that having the gate up, when driving
on a good dry road, offers a slight advantage in milage. I do not know
whether this would be true under wet conditions, where tire-road
contact is otherwise weakened by the water.
factor outweighs the other.
The first is the added weight that having the tailgate down puts
on the rear tires. More weight means better road contact.
The second is wind resistance. You might think that having the gate
up creates resistance. And it does until a certain point, at which time
a pressurized pocket of air is formed in the closed bed. The outside
air flows more smoothly *over* this pocket than it does flowing over
the cab bed (as it would if the gate were left down or off).
So, whether the benefit of the added weight distribution gained by
having the gate down outweighs the benefit of having the air pocket
when it is up is the question, and this can only be borne out by
experimental testing. That is, drive each way and check your milage.
I believe it has been published that having the gate up, when driving
on a good dry road, offers a slight advantage in milage. I do not know
whether this would be true under wet conditions, where tire-road
contact is otherwise weakened by the water.
New User
Joined: Jan 2005
Posts: 23
Likes: 0
Lift is caused by high pressure on the underside of an airplane wing.
In the case of the truck, the pressure is on the upper side, thus
creating the opposite of lift.
In any case, lift is not changing the weight on the truck,
and it still takes the same amount of energy to move that mass.
What it does effect is the coefficient of friction (grip) of the
tires to the road. You get better grip, and less rolling slip,
the higher the weight on the drive (rear) tires is. This isn't
changing the weight of the truck, just the amount of
force on the rear tires.
In the case of the truck, the pressure is on the upper side, thus
creating the opposite of lift.
In any case, lift is not changing the weight on the truck,
and it still takes the same amount of energy to move that mass.
What it does effect is the coefficient of friction (grip) of the
tires to the road. You get better grip, and less rolling slip,
the higher the weight on the drive (rear) tires is. This isn't
changing the weight of the truck, just the amount of
force on the rear tires.
Cargo Master
Joined: Jun 2003
Posts: 2,203
Likes: 0
From: Carlsbad, California
Mixing weight and mass in the same sentence and making me think . . . 
Depending upon how much traction you need, having some lift to reduce the downward force on the truck might reduce the rolling resistance slightly.
I think though that the lift would come at the expense of drag since nothing's free and it is going to take some power to lift a 7000 lb truck enough to decrease the rolling resistance.
Then there's trying to turn with less downward force on the tires - not good.
Probably better to pump up the tires as someone else said, then keep the tailgate up, fold in the mirrors, remove the external antenna, and start cleaning up the air under the truck.
What I wonder is how much a spoiler in the bed of the truck would help move air around my toy hauler - tag not 5vr - and save some fuel . . . ?
Depending upon how much traction you need, having some lift to reduce the downward force on the truck might reduce the rolling resistance slightly.
I think though that the lift would come at the expense of drag since nothing's free and it is going to take some power to lift a 7000 lb truck enough to decrease the rolling resistance.
Then there's trying to turn with less downward force on the tires - not good.
Probably better to pump up the tires as someone else said, then keep the tailgate up, fold in the mirrors, remove the external antenna, and start cleaning up the air under the truck.
What I wonder is how much a spoiler in the bed of the truck would help move air around my toy hauler - tag not 5vr - and save some fuel . . . ?
Originally Posted by txag
Lift is caused by high pressure on the underside of an airplane wing.
In the case of the truck, the pressure is on the upper side, thus
creating the opposite of lift.
In any case, lift is not changing the weight on the truck,
and it still takes the same amount of energy to move that mass.
What it does effect is the coefficient of friction (grip) of the
tires to the road. You get better grip, and less rolling slip,
the higher the weight on the drive (rear) tires is. This isn't
changing the weight of the truck, just the amount of
force on the rear tires.
In the case of the truck, the pressure is on the upper side, thus
creating the opposite of lift.
In any case, lift is not changing the weight on the truck,
and it still takes the same amount of energy to move that mass.
What it does effect is the coefficient of friction (grip) of the
tires to the road. You get better grip, and less rolling slip,
the higher the weight on the drive (rear) tires is. This isn't
changing the weight of the truck, just the amount of
force on the rear tires.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Originally Posted by txag
Lift is caused by high pressure on the underside of an airplane wing.
In the case of the truck, the pressure is on the upper side, thus
creating the opposite of lift.
In any case, lift is not changing the weight on the truck,
and it still takes the same amount of energy to move that mass.
What it does effect is the coefficient of friction (grip) of the
tires to the road. You get better grip, and less rolling slip,
the higher the weight on the drive (rear) tires is. This isn't
changing the weight of the truck, just the amount of
force on the rear tires.
In the case of the truck, the pressure is on the upper side, thus
creating the opposite of lift.
In any case, lift is not changing the weight on the truck,
and it still takes the same amount of energy to move that mass.
What it does effect is the coefficient of friction (grip) of the
tires to the road. You get better grip, and less rolling slip,
the higher the weight on the drive (rear) tires is. This isn't
changing the weight of the truck, just the amount of
force on the rear tires.