Strange issue, with only rear windows down.

jpowers

jpowers

New member
Ok, so I had my front windows tinted last Friday. The said not to roll them down for 4 days, this odd in it's self never had heard that before but went along with it.

So today on my way home from work, I wanted some fresh air. Since I had 1 more day left for the recommended wait on the front windows. I rolled the rear windows down, and the whole roof/body of the truck started to vibrate. It was pretty obvious it was from the air pressure. I opened the moon roof, problem went way, so I closed it and it was back. I opened the rear tailgate window it went way. This only happens at highway speeds 40+.

Just wonder if anyone else has come across this.
 
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jpowers said:
Ok, so I had my front windows tinted last Friday. The said not to roll them down for 4 days, this odd in it's self never had heard that before but went along with it.

So today on my way home from work, I wanted some fresh air. Since I had 1 more day left for the recommended wait on the front windows. I rolled the rear windows down, and the whole roof/body of the truck started to vibrate. It was pretty obvious it was from the air pressure. I opened the moon roof, problem went way, so I closed it and it was back. I opened the rear tailgate window it went way. This only happens at highway speeds 40+.

Just wonder if anyone else has come across this.
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Seems to be a common aero thing w/ hatchbacks/wagons/SUVs. My GTI does it and my mom's Rav4 does it. Basically, the air is spilling into the back windows equally on each side and it, harshly, hits the stagnant air held in the hatch/cargo area. By opening the moonroof or gate glass, you've created a path for air to flow through.

If you open the windows at different amounts (one fully open, and one half open), you created a differential between the amount of air trying to come in and you shouldn't get the vibration. With both back windows fully down, you have the same amount of air trying to push in with nowhere to go.

It isn't an aerodynamic defect so much as it is just the nature of the beast. You're going to see a similar effect on any 2 box design w/ the middle row windows open.

<--- speculating from degree in Aerospace Engineering
 
Quentin said:
Seems to be a common aero thing w/ hatchbacks/wagons/SUVs. My GTI does it and my mom's Rav4 does it. Basically, the air is spilling into the back windows equally on each side and it, harshly, hits the stagnant air held in the hatch/cargo area. By opening the moonroof or gate glass, you've created a path for air to flow through.

If you open the windows at different amounts (one fully open, and one half open), you created a differential between the amount of air trying to come in and you shouldn't get the vibration. With both back windows fully down, you have the same amount of air trying to push in with nowhere to go.

It isn't an aerodynamic defect so much as it is just the nature of the beast. You're going to see a similar effect on any 2 box design w/ the middle row windows open.

<--- speculating from degree in Aerospace Engineering
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kind of my thoughts to.I've for the most part always owned 2dr coupe's so the experience was new to me. I never tried it on the limited so don't know if it's only my trail that does it. You can however crack it about 1/3 the way down and it doesn't happen.
 
jpowers said:
Ok, so I had my front windows tinted last Friday. The said not to roll them down for 4 days, this odd in it's self never had heard that before but went along with it.

So today on my way home from work, I wanted some fresh air. Since I had 1 more day left for the recommended wait on the front windows. I rolled the rear windows down, and the whole roof/body of the truck started to vibrate. It was pretty obvious it was from the air pressure. I opened the moon roof, problem went way, so I closed it and it was back. I opened the rear tailgate window it went way. This only happens at highway speeds 40+.

Just wonder if anyone else has come across this.
Click to expand...

Know how when you blow across the top of an empty Coke bottle it makes a tone? Basically, your vehicle is doing the same thing, only you are sitting inside the bottle.

Found this nice explanation for the phenomenon on a Google search:

The pulsations begin as a feedback phenomenon: as air passes the leading edge of the open window, vortices (swirls) of air are created. These then hit the trailing side of the window frame creating a sound wave. Part of that sound wave is projected forward to the leading edge again, where it triggers another vortex. (here’s a schematic representation). At certain speeds, this feedback process will settle into a pattern where the vortices are created in ever stronger rhythmic pulses.

This phenomenon is the source of the original vibration, but this alone doesn’t account for the strong pulsing you fell in the car. This happens because the interior of the car is a (nearly) closed cavity of air having a fixed volume. This cavity of air, like the air inside a pop bottle, has a particular resonant frequency. The bigger the cavity, the lower the resonant frequency. If you supply a source of vibration that matches this resonant frequency, then you’ll get that whole volume of air pulsing to that beat.

In the case of the car, at some speed the vibration set up by the vortex feedback mechanism will match the resonant frequency of the air inside the car and that whole volume of air will start pulsing right along. Opening another window creates a situation where you no longer have a fixed volume of air in the car, because air can move freely in an out that other window. So the inside of the car no longer has a resonant frequency. The open windows are still creating rhythmic vibrations, but they won’t set the air in the car pulsing.
 
jpowers said:
kind of my thoughts to.I've for the most part always owned 2dr coupe's so the experience was new to me. I never tried it on the limited so don't know if it's only my trail that does it. You can however crack it about 1/3 the way down and it doesn't happen.
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When I did this for the first time in the Range Rover (traded for the runner) I thought my head was going to pop and roof was gunna blow off. Its normal.
 
The scientists above gave all the right technical info- but thought you would feel better knowing this happens on my 3rd Gen 4runner and my brother's 4th Gen 4runner too! Take it for what it is and use your rear window to allow air to escape. Besides, it makes Jeep, Ford, Chevy, and other SUV guys jealous they can't drop their rear window. :dancin:
 
psquared77 said:
The scientists above gave all the right technical info- but thought you would feel better knowing this happens on my 3rd Gen 4runner and my brother's 4th Gen 4runner too! Take it for what it is and use your rear window to allow air to escape. Besides, it makes Jeep, Ford, Chevy, and other SUV guys jealous they can't drop their rear window. :dancin:
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Hell yeah, love that rear window drop!
 
My brother has a Ford SUV that the rear window rolls down. We're not the only ones with that feature....
 
very interesting explanations. I have had this happen to all of my 4 door vehicles as well.

I didn't know that Ford sells a SUV with a roll down window?? I know the Explorer and Expedition don't roll down. I didn't think the new Escape did either but could be wrong. Thats all of there SUVs, unless you count that wagon looking Flex. I know several full size trucks have a power roll down window. The Ford Explorer Sport Trac (what I drive) also has a roll down rear window, but it is not an SUV, its a truck.
 
He's got a full-size Bronco that he uses mostly to plow his 1000 ft driveway. It has a power rear window, just like us:)
 
Jed said:
He's got a full-size Bronco that he uses mostly to plow his 1000 ft driveway. It has a power rear window, just like us:)
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That vehicle hasn't be made in 14 years. The 1959 Lincoln Continental also had a power rear window. I mention that because it's just as relevant as you bringing up your brother's Bronco.

However, as the 4Runner is the only SUV currently for sale in the US with that feature, it's entirely accurate to say we are the only ones who have it. Bringing up cars that are no longer made is called "nit picking", which is all you seem to do in the 5th Gen section.
 
SeattleMike said:
That vehicle hasn't be made in 14 years. The 1959 Lincoln Continental also had a power rear window. I mention that because it's just as relevant as you bringing up your brother's Bronco.

However, as the 4Runner is the only SUV currently for sale in the US with that feature, it's entirely accurate to say we are the only ones who have it. Bringing up cars that are no longer made is called "nit picking", which is all you seem to do in the 5th Gen section.
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It just won't end, will it? Geez... some people need to get a hobby.
 
Jed said:
My brother has a Ford SUV that the rear window rolls down. We're not the only ones with that feature....
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Correct. Ford also made that Explorer Sportrac truck/suv mix for several years that had the option to lower the rear window. I have a good friend that bought his Sportrac 2 months before I bought my '02 Runner.....8 years later he is on his 3rd Ford Explorer and I still have my Runner :boink:
 
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