Why Do Trucks Come From Factory With Nose Dive?

Barganier · July 30, 2008

Mine did (Z71 4WD) not but I am curious why they come like this and everyone has to get a leveling kit. That would be except for those of us that have 4WD's.

soludsnake · July 30, 2008

Mine did (Z71 4WD) not but I am curious why they come like this and everyone has to get a leveling kit. That would be except for those of us that have 4WD's.

So that when their is weight in the bed, like truck are built to have the truck sits level. Otherwise the back would drop and drag when the bed was full. Trailers also comes in to play.

Barganier · July 30, 2008

Mine did (Z71 4WD) not but I am curious why they come like this and everyone has to get a leveling kit. That would be except for those of us that have 4WD's.

So that when their is weight in the bed, like truck are built to have the truck sits level. Otherwise the back would drop and drag when the bed was full. Trailers also comes in to play.

Ahhhhh Thanks

L29er · July 30, 2008

yeah and i think fuel economy too

soludsnake · July 30, 2008

yeah and i think fuel economy too

I believe your right on that one as well. The dip of the front allows for air to pass over the truck more easily creating less resistance when driving at higher speeds. This is also why they added the lower valance (supposedly), allowing air to be directed by it.

-Rhys

2000DV4.8 · July 30, 2008

Yup, so the rear doesn't sag when it's loaded down, and for aerodynamics.

tobias · July 30, 2008

Dan takes advantage of the rake to conceal the fat chicks he stuffs under his bed cover on the weekends. He has nosy neighbors so he has to be really careful.

HawkeyeOC · July 30, 2008

Dan takes advantage of the rake to conceal the fat chicks he stuffs under his bed cover on the weekends. He has nosy neighbors so he has to be really careful.

I always wondered how he knew exactly how much weight his truck holds down to the last pound

2000DV4.8 · July 30, 2008

Dan takes advantage of the rake to conceal the fat chicks he stuffs under his bed cover on the weekends. He has nosy neighbors so he has to be really careful.

Eeeyap! That's why I need to replace my leaf springs...

99silverado1500 · July 30, 2008

Id rather have it come level from the factory though and drag bumper hauling stuff it makes it look like you really loaded the truck down lol makes sure everyone knows the true capabilities of a chevy!!

5.3Avalanche · July 30, 2008

yeah and i think fuel economy too

I believe your right on that one as well. The dip of the front allows for air to pass over the truck more easily creating less resistance when driving at higher speeds. This is also why they added the lower valance (supposedly), allowing air to be directed by it.

-Rhys

I somewhat disagree with the aerodynamics comment. Aerodynamics is a study of how easily an object can cut through the air. Drag force which is part of aerodynamics is a measure of how the effect of the air holds back an object as it's pushed through the air by a force. Drag force is a function of a few things: the velocity of the object, the density of the fluid (the air), the viscosity of the fluid (the air) and the frontal area of the object. By tipping up the back end of the truck, you create more downforce at a high speed, and you actually increase the drag force. Some might offer a comparison to a Corvette as an example and ask, "well, why is a corvette sloped towards the front?" For one thing, the corvette is very narrow at the front and offers much less frontal area so it's not necessarily that bad to tip the top of the car towards the front- the corvette has a very low coefficient of drag. Also, Corvettes are made to produce downforce at high speed as downforce is a funciton of forward velocity and helps maintain grip on the tires. Sloping an object into the wind actually converts a component of the moving fluid to slow down that object. This would mean you'd get worse fuel economy. The tilt of the truck is mostly due to the load factor of what a pickup is supposed to handle. Nobody wants a truck that drags on the ground when loaded. Look at a silverado SS or a similar sport truck. They are not tilted as much as they're not meant to carry the same amount of weight.

soludsnake · July 30, 2008

yeah and i think fuel economy too

I believe your right on that one as well. The dip of the front allows for air to pass over the truck more easily creating less resistance when driving at higher speeds. This is also why they added the lower valance (supposedly), allowing air to be directed by it.

-Rhys

I somewhat disagree with the aerodynamics comment. Aerodynamics is a study of how easily an object can cut through the air. Drag force which is part of aerodynamics is a measure of how the effect of the air holds back an object as it's pushed through the air by a force. Drag force is a function of a few things: the velocity of the object, the density of the fluid (the air), the viscosity of the fluid (the air) and the frontal area of the object. By tipping up the back end of the truck, you create more downforce at a high speed, and you actually increase the drag force. Some might offer a comparison to a Corvette as an example and ask, "well, why is a corvette sloped towards the front?" For one thing, the corvette is very narrow at the front and offers much less frontal area so it's not necessarily that bad to tip the top of the car towards the front- the corvette has a very low coefficient of drag. Also, Corvettes are made to produce downforce at high speed as downforce is a funciton of forward velocity and helps maintain grip on the tires. Sloping an object into the wind actually converts a component of the moving fluid to slow down that object. This would mean you'd get worse fuel economy. The tilt of the truck is mostly due to the load factor of what a pickup is supposed to handle. Nobody wants a truck that drags on the ground when loaded. Look at a silverado SS or a similar sport truck. They are not tilted as much as they're not meant to carry the same amount of weight.

This is true, and you have proven that you know far more about the mechanics of aerodynamics then I do.

Would a tonneau cover change the balance of the force on the rear? Or dropping the tailgate? Flowing air after its moved over the cab and into the box with no resistance produces less drag am I right? Had their been no cover or the tailgate closed the air would get held up and cause drag on the tail gate correct?

VMax2007 · July 30, 2008

Dan takes advantage of the rake to conceal the fat chicks he stuffs under his bed cover on the weekends. He has nosy neighbors so he has to be really careful.

At least his fit under the bed cover.

99silverado1500 · July 30, 2008

yeah they arent as bad as unit, he has a cap for the BIGGG Ones lol jkkk

5.3Avalanche · July 31, 2008

yeah and i think fuel economy too

I believe your right on that one as well. The dip of the front allows for air to pass over the truck more easily creating less resistance when driving at higher speeds. This is also why they added the lower valance (supposedly), allowing air to be directed by it.

-Rhys

I somewhat disagree with the aerodynamics comment. Aerodynamics is a study of how easily an object can cut through the air. Drag force which is part of aerodynamics is a measure of how the effect of the air holds back an object as it's pushed through the air by a force. Drag force is a function of a few things: the velocity of the object, the density of the fluid (the air), the viscosity of the fluid (the air) and the frontal area of the object. By tipping up the back end of the truck, you create more downforce at a high speed, and you actually increase the drag force. Some might offer a comparison to a Corvette as an example and ask, "well, why is a corvette sloped towards the front?" For one thing, the corvette is very narrow at the front and offers much less frontal area so it's not necessarily that bad to tip the top of the car towards the front- the corvette has a very low coefficient of drag. Also, Corvettes are made to produce downforce at high speed as downforce is a funciton of forward velocity and helps maintain grip on the tires. Sloping an object into the wind actually converts a component of the moving fluid to slow down that object. This would mean you'd get worse fuel economy. The tilt of the truck is mostly due to the load factor of what a pickup is supposed to handle. Nobody wants a truck that drags on the ground when loaded. Look at a silverado SS or a similar sport truck. They are not tilted as much as they're not meant to carry the same amount of weight.

This is true, and you have proven that you know far more about the mechanics of aerodynamics then I do.

Would a tonneau cover change the balance of the force on the rear? Or dropping the tailgate? Flowing air after its moved over the cab and into the box with no resistance produces less drag am I right? Had their been no cover or the tailgate closed the air would get held up and cause drag on the tail gate correct?

Without putting the different objects into a windtunnel, I could not tell you accurately what would happen EXACTLY for the scenarios that you've listed. One thing I do know is that a truck will have LESS drag force if the tailgate is UP as compared to when it is down! I will try to explain the theory behind this as simply as I can. There is a simple fluid dynamics explanation for this. I don't know of your knowledge on this subject but every fluid exhibits a shear force. For example, if you take something that spins (a smooth, round circular disc for example with a shaft coming off the end) and spin it in the open air, and then spin it in a tub of water, you will realize that it is harder to spin in the water. This is because the viscosity difference between air and water affects the motion of an object. With a truck, air flowing over a surface that is parallel to the flow of the air will cause it to slow down due to shear. This force is typically called "fluid wall shear" and contributes to drag. This shear force is made GREATER when then tailgate of a truck is open as the air will come off the top of the cab of the truck, then dip down low and hit the bed. It will then run straight along the bed and then exit out the open tailgate. In contrast, a bed with a closed tailgate will behave much differently. In this scenario, air actually comes off of the cab, dips down into the bed, and a large vortex begins to form in the bed. This vortex is a spinning mass of air that appears to stay with the truck in a rotating-stagnant form. As this vortex is created while driving, it serves as a kind of blocker for the air that is next coming up over the cab. This next air approaches the bed but by this time there is already a vortex there which deflects the air up and over the tailgate. So while air may first hit the tailgate at first, as time passes, this mass of air begins to rotate in the bed. At some point or another you may have seen a truck with some kind of loose news paper in the bed driving down the highway as I've seen. In this scenario, the papers will actually stay in the bed that is fully open and may appear to swirl in a circle because of this vortex.

As for a tonneau cover, I don't know for sure but I would estimate that a truck with a tonneau cover would produce less drag force than one without a tonneau. Basically, the goal to making something aerodynamic is to make the object appear as much like the cross section of an airplane wing as possible.

As a base guideline for numerical comparison, a sphere with diameter 'x' will exhibit a typical coefficient of drag of 1.2. If that same sphere is made into an ellipse where the height is still 'x' but now the length is '2x', then your coefficient of drag is cut in half to 0.6. If you make the length of the ellipse now to something greater than '4x', taper the back end of the ellipse so it converges to a single point and maintain that the height is still 'x', then your coefficient of drag is approximately 0.1 or roughly 10 times smaller than the original sphere. By adding a tonneau cover, you are changing the shape of the truck to approximate the shape that I'm describing below thus effectively "streamlining" it. I hope this all at least makes a little sense. Let me know if you have questions.