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      12-16-2008, 03:10 AM   #1
Big Windy
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Crash Protection- '08 vs. 09' w/Active Head Restraint

Well, the M3 headrests have long since been an important topic on here, but when the 09 models were first released there was some talk about the loss of tilt functionality due to BMW's Active Head Restraint (AHR) system. Nobody has really said anything about AHR since.

Some results were just published by the Insurance Institute for Highway Safety on the 3 series' AHR headrests and how they compare to the non-AHR headrests. The first link below has some fairly detailed data on backset (how far the headrest is from your head), head contact time, max shear neck force, max neck tension, and a few other categories. The bottomline is that the non-AHR headrests receive an Acceptable rating (2nd best), while the AHR headrests receive a Good rating (best). I was most surprised that the AHR system eliminates the 90N max shear force and almost cuts the max neck tension that is seen with the non-AHR rests in half, despite a greater backset and top of the head distance. I still have yet to see a demonstration of these head restraints in a crash, but I would like to see a video after seeing this data.

The test doesn't say anything specific to the M3, but I thought that some of you might take interest in the general data and test results. The second link shows more detailed and scientific information about how the tests are conducted for all nerds and naysayers.

I should also mention that these particular tests were done by striking the vehicle from the rear with a vehicle of similar weight at 20 mph.

http://www.iihs.org/ratings/head_res...spx?bmw#tested

http://www.iihs.org/ratings/head_res...aint_info.html

Enjoy.
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      12-16-2008, 03:12 AM   #2
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Are you sure the 09 M3 has AHR? The seats look exactly the same to me.
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      12-16-2008, 04:05 AM   #3
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Originally Posted by FStop7 View Post
Are you sure the 09 M3 has AHR? The seats look exactly the same to me.
09 M3 definitely has AHR. The seats are the same, but the headrests are different. They look similar, but the main thing is that they don't tilt.
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      12-16-2008, 04:12 AM   #4
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09 M3 definitely has AHR. The seats are the same, but the headrests are different. They look similar, but the main thing is that they don't tilt.
And they also can't be removed. They will adjust up and down. The rear ones can be removed and so they are not AHR's...only the front two.
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      12-16-2008, 07:41 AM   #5
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IIHS site appears to be down right now.

I stilll love my tilt headrests, even if they aren't as good as the new ones in an accident. It will be interesting selecting my next BMW when the time comes, without tilt headrests. Seems like they could still allow tilt if it relied on something more than friction to keep its position. Maybe they'll have that figured out by the time the F30 3 series debuts
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      12-16-2008, 11:22 AM   #6
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I have an 09 with the AHR, and I have no issues with them. I don't normally rest my head on the head rest when driving, but I like knowing it is in a fixed position and close to the back of my head. Even when I do lean my head back it feels comfortable.
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      12-16-2008, 04:13 PM   #7
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I didn't think the 08 headrests could be tilted, I thought they just went up and down. Maybe it's because I have an E90?
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      12-16-2008, 06:03 PM   #8
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I didn't think the 08 headrests could be tilted, I thought they just went up and down. Maybe it's because I have an E90?
Pretty sure all '08 head rests tilt, even e90.
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      12-16-2008, 07:02 PM   #9
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Good information OP
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      12-16-2008, 07:38 PM   #10
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Quote:
Originally Posted by mkoesel View Post
It will be interesting selecting my next BMW when the time comes, without tilt headrests. Seems like they could still allow tilt if it relied on something more than friction to keep its position. Maybe they'll have that figured out by the time the F30 3 series debuts
They can't tilt because they (BMW engineers) wouldn't know how far away the headrest is from your estimated head position. It's not just the headrest that's different, it's all the mechanicals in the seat under the headrest that's different. These suckers are suppose to shoot forward in an accident to essentially catch your head before it slams into the headrest.

I just wonder if BMW used the mechanical mechanism or some pyrotechnical one that needs to be replaced once it's activated.
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      12-16-2008, 07:47 PM   #11
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Good information OP
Agreed. Thanks OP!!!
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      12-16-2008, 08:09 PM   #12
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Good post. I recall a thread bemoaning the new requirements, seems that they are surely worth losing the tilt feature of the 2008 death traps.
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      12-16-2008, 08:18 PM   #13
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Quote:
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They can't tilt because they (BMW engineers) wouldn't know how far away the headrest is from your estimated head position. It's not just the headrest that's different, it's all the mechanicals in the seat under the headrest that's different. These suckers are suppose to shoot forward in an accident to essentially catch your head before it slams into the headrest.
That seems insane. Now, I am not disagreeing with you, since I have no idea how these work and you sound like you have at least some idea.

But if this is good, then why isn't it similarly good to have the seat back itself normally a set distance from your back, and then only "shoot forward" in a crash? What is so special about the head/neck that it would make more sense for the safety system to operate this way, instead of just cradling your head to begin with? You know, like it would in racecar?
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      12-16-2008, 08:21 PM   #14
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They should just use bulletproof glass.
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      12-17-2008, 02:02 AM   #15
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Quote:
Originally Posted by mkoesel View Post
That seems insane. Now, I am not disagreeing with you, since I have no idea how these work and you sound like you have at least some idea.

But if this is good, then why isn't it similarly good to have the seat back itself normally a set distance from your back, and then only "shoot forward" in a crash? What is so special about the head/neck that it would make more sense for the safety system to operate this way, instead of just cradling your head to begin with? You know, like it would in racecar?
I would really like to see a crash demonstration to see how these head rests work, because I can't really visualize it on my own. From what I understand though, the headrests absorb the impact by first extending towards the occupant's head at the onset of the crash and then gradually (although this all happens in a split second) placing a diminishing force against the head to counteract whiplash. The reason why the headrest cannot tilt is because the tilt would change the backset and the top of the head distance and, therefore, would allow an unwanted variable into whatever equation or algorithm these headrests use to do their thing in a crash.

Okay, now I'm confused Anybody want to videotape themselves getting rear ended?
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      12-17-2008, 03:00 AM   #16
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Quote:
Originally Posted by Big Windy View Post
I would really like to see a crash demonstration to see how these head rests work, because I can't really visualize it on my own. From what I understand though, the headrests absorb the impact by first extending towards the occupant's head at the onset of the crash and then gradually (although this all happens in a split second) placing a diminishing force against the head to counteract whiplash. The reason why the headrest cannot tilt is because the tilt would change the backset and the top of the head distance and, therefore, would allow an unwanted variable into whatever equation or algorithm these headrests use to do their thing in a crash.

Okay, now I'm confused Anybody want to videotape themselves getting rear ended?
I understand what you are saying Big Windy, but it still seems like not having your head move in the first place would always be better than "catching" it when it did move. Even the link at the IIHS site says:

"The backset, or distance behind the head, should be as small as possible."

Ok, well how bout zero? That's as small as you can get. But, by not having tilting head rests, you make the liklihood of the backset being zero less. So why is that good? To me the best way to do it would be allow the headrest to adjust and then lock into place, like I said earlier. But hey, I am certainly no safety engineer.

Also, since the headrests still move up and down (right?) then the "height" measurement on the IIHS site can also be changed. So why allow that to change still, if its also safety concern?
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      12-17-2008, 03:37 AM   #17
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Quote:
Originally Posted by mkoesel View Post

Also, since the headrests still move up and down (right?) then the "height" measurement on the IIHS site can also be changed. So why allow that to change still, if its also safety concern?
Nope...no up and down...
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      12-17-2008, 11:40 AM   #18
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Quote:
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Okay, now I'm confused Anybody want to videotape themselves getting rear ended?
Hey BW, I volunteer mkoesel
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      12-17-2008, 11:43 AM   #19
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I thought the metal shafts still allow you to move the headrests up and down. I know the active headrests in my Nissan Frontier allow the headrests to move up and down on the metal shafts.
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      12-17-2008, 12:30 PM   #20
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Quote:
Originally Posted by Big Windy View Post
Nope...no up and down...
Wow, that's surprising. I rely on both the tilt and elevation controls for comfortable head position. I would be lost without those.

Quote:
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Okay, now I'm confused Anybody want to videotape themselves getting rear ended?
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Hey BW, I volunteer mkoesel
Hey, what you guys want to watch in the privacy of your own home is your business. Just leave me out of it.

j/k guys
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      12-17-2008, 12:31 PM   #21
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Originally Posted by mkoesel View Post
Wow, that's surprising. I rely on both the tilt and elevation controls for comfortable head position. I would be lost without those.





Hey, what you guys want to watch in the privacy of your own home is your business. Just leave me out of it.

j/k guys
hahahahaha, i totally didn't even see that.
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      12-17-2008, 11:49 PM   #22
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Quote:
Originally Posted by Laszlo View Post
Why doesn't anyone post pics of those beauties? The '09 "Toaster-from-the-50s-head-rests?"

They are the most hideous headrests I've ever seen. Sorry.
You mean the 2009 E93 headrests. Mine look just like the 2008s do.
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