I've had my xB for approx 1 month now and I just drove it for the first time on the freeway. I had my best buddy (My dog) riding in the back and he was a bit warm and wanted some air. When I dropped the rear windows havoc broke out and I thought I was losing a tire or something. The rig was shaking and it sounded like a helicopter was hovering right over me, my ears started hurting from the air pressure and I had to close the windows.

I was curious then and tried several different configurations, Windows crack down 2-3 inches, seats down, seats up, left window right window etc... the only way I can drive on the freeway with rear windows down is to open the fronts.

Has anyone else noticed this? Could it be an issue or danger to people?

Should I go to the dealership and have them test another rig?

It's black fully stock, only mod is windows tinted.

 

Do a search... This is common for MANY cars... And was thoroughly discussed for the first gen xB and xA

 

Yea it did it in my 1st gen too, also in my second gen. Cure for this is to open both rear windows.

 

It's called harmonic distortion. You ever blow over over the opening of a beer or coke bottle? Well, you're actually in the beer or coke bottle. It's also the same principal that creates music from a flute.

Now, when the harmonic distortion = the natural frequency of an object, that's when when all hell breaks loose. You ever see the video of the bridge in Washington going all wibbly-wobbly (yes, that's a technical term )? That's what happened there. The wind going over the bridge created a harmonic distortion that was equal to the bridge's natural frequency (one thing psychics and physicists agree on: everything vibrates). As the winds picked up speed, it added amplitude to the bridge's wave, and it eventually destroyed the bridge.

 

I noticed this in my xb and in my Dodge pickup also with 4 doors. I fix it by cracking the front windows.

 

btw, the B is standard equipped with air conditioning. If you're traveling over 40mph, the drag you create by dropping your window will cost you more fuel than by turning on the a/c.

 

Good point.

And also, if the airbags deploy with the windows down, there is a greater chance of hearing damage. For some reason, when the windows are up, the pressure is more equalized and your ears are able to deal with it a little better.

 

I noticed this effect when I wanted to blow out the hot air leaving work. Turned the rear windows down and at around 40mph, the "wabbellywab" started. Interesting effect but not something I would want to discover at 80mph! Lucky the rear window is glued in very good :p

 

Here is a video of the Tacoma Narrows bridge.
http://www.youtube.com/watch?v=P0Fi1VcbpAI

 

Excellent description, Panama Jack, except "distortion" should be "resonance." (Helmholtz resonator for those inclined to look things up...)

I especially liked when you explained they were IN the beer bottle.

The Tacoma Narrows Bridge, "Galloping Gerdy," is an excellent example of harmonic resonance gone wild. http://www.history.com/media.do?acti...dges_broadband

Anyway, back to the problem, try one front window down a bit and the opposite rear window down a bit more. That often disrupts the harmonics enough with the flow of air that the problem doesn't have a chance to establish itself.

Good luck!
Tom

P.S. Here's an excellent clip of Galloping Gerdy, although the 'narration' is pretty 'dry.' http://www.youtube.com/watch?v=3mclp9QmCGs

 

SAME problem with my '94 Corolla. There's no chance I can have JUST the back windows open when doing highway speeds. Though, just the front windows cause drag too, so i always have the back windows at least 1/4 down if the fronts are.

 

same in my old Jetta. Crack the front = the only thing I found that works too

 

So uhm, are you saying that by having both front and back windows open, the air just sort of slips out the back windows negating the drag? If so, sorry to inform, but that's not correct.

The best case scenerio at highway speeds is, bar none, windows up, a/c on. FYI, above 40 mph, almost every bit of your engine power is being used to punch you through the wind. Drag is everything, absolutely everything for hwy mileage. That's why a 600 hp Z06 Corvette gets 28mpg hwy (at 55 ph). And as you move up in speed, the wind keeps getting thicker and thicker. I would not advise sticking an arm out of your window above 120 mph. Not sure what would happen, but I imagine it might hurt a bit.

 

i never said there was NO drag with all the windows down, but there is LESS. instead of filling 3' of space with air being slammed in the back window, it's only 1.5', the air gets pushed out the window quicker. (but I can't win w/ the tC, 2 doors = 2 'front' windows = sucks. No real complaints about the convertible - top down)

and I'm hoping you're assuming that you HAVE to cool your self down one way or the other, and that's why the AC is on. otherwise, windows up, and nothing on is best. obviously.

though if i cared that much about squeezing every last bit of mpg out of the car, i'd also take off my roof racks and get rid of my sub, and the 15lbs of random fluids i keep in the trunk. but at normally 35mpg for a car w/ as many miles as it has, i'm not gonna complain.

 

The difference would be negilible. Once the wind leaves the surface of your window, and goes into the car, the drag is created. Even if you knocked out your back window, you're still much better off (milage wise) leaving the windows up.

And while we're on it, you're also better off, milage wise, leaving your tailgate closed on a p/u truck.

And yes, I live in Florida, so I have no concept of being in an automobile without the a/c on. ;-)

 

Did know that one. Mythbusters FTW. ;)

 

I always crack the back window half way and open the driver's window all the way. My friend let me drive his Gen 2 xB the other day and I did the back window without even thinking about it. I meant to ask him if it had the same issue, but now I know and it's not surprising.

 

Well thanks to you all for the answers. I was just a bit surprised at how bad the rig shook. I would more than likley never open the rears without the front being open but I was running my Dog to the Vet and he was not doing too good and I thought it would be nice to give him some air.

Thanks again.

Skip

 

Nope doesn't help. I thought the xB did it bad. Now to know the xB2 does it also makes me feel better!
Hey, something the xB and the xB2 actually have in common besides the name.

 

I've never gotten better mileage with the AC on versus driving with the windows down, ever.

For all of you Mythbusters fans, they took on that "myth" and proved that riding with the windows down yielded better mileage. I think they used two Explorers and put 10 gallons in each and drove around a track at 55 MPH. The Explorer with the AC on ran out of gas long before the one with the windows down.