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Old 30th August 2009, 19:29   #1
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Default How To Check If My Seat Belt Will Work In An Accident?

As an habit I always wear my seat belts even before switching the ignition. And also as an habit I give the seat belt a small tug just to check if the seat belt is working/ fixed properly.

On giving it a tug with hand, most of the times, the seat belt gets stuck and doesnt loosen (how it is supposed to be). But some times the seat belt comes all the way out.

While driving, on and off I keep moving my torso forward just to check if the seat belt is holding my upper body back. Most of the time it doesnt and let the body move all the way forward to the steering wheel.

This is not just the case with my car, I tried it with my dad's car and there too the seat belt action was the same.

Am I just over reacting here? How can I check if the my seat belt is working and will hold my body back in a real accident situation?

Is there a way to check the same?
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Old 30th August 2009, 19:38   #2
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I guess the feature you are talking about are pretensioning seatbelt.

quoting from wikipedia - 'Pretensioners preemptively tighten the belt to prevent the occupant from jerking forward in a crash. Mercedes-Benz first introduced pretensioners on the 1981 S-Class. In the event of a crash, a pretensioner will tighten the belt almost instantaneously. This reduces the motion of the occupant in a violent crash. Like airbags, pretensioners are triggered by sensors in the car's body, and most pretensioners use explosively expanding gas to drive a piston that retracts the belt. Pretensioners also lower the risk of "submarining", which is when a passenger slides forward under a loosely worn seat belt.'

I do not think there is actually a way to check if your pre tensioner is working or not. Can any expert comment on the same?

Last edited by blackasta : 30th August 2009 at 19:40.
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Old 30th August 2009, 19:44   #3
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Exactly!! Even when I move my torso forward with a jerk the pre tensioner does not work and the body moves to the steering wheel. Its scary hence I started this thread!!
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Old 30th August 2009, 20:11   #4
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weird. its working to the point of being irritating in my swift D
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Old 30th August 2009, 20:15   #5
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Hold your belt in your hand and give it a hard tug suddenly. If you find that it stops immediately, your seatbelt is fine.

IIRC Pretentioners are something else which are not available on regular cars.

You may want to take a looksie at this linky.
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Old 30th August 2009, 20:20   #6
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The nature of the seatbelt where it locks down when you try to pull at it at a quick pace is due to a device called an inertia reel. As long as the seatbelt refuses to give when you tug at quickly, this feature is working.

It is supposed to let you move around in the seat and lean to the front during normal operation. How would you reach over to open the glove box when belted up, for example? When you are in a crash, the energies are much more and seatbelts are designed to lock only then.

Pretentioners are a different mechanism. This is used to provide an additional layer of security. It was found that the lap belt in a normal three point harness would be loose enough that you could injure yourself by hitting the roof in a roll over situation or slide under the belt and go under the steering column. To prevent this, when the car detects a crash situation, pins connected to the belt are fired with explosives which fasten the seatbelt down with some serious force. It is enough to damage skin, but that is better than a broken neck in case of a roll over.

@toiingg : Pretensioners are standard in a surprisingly large number of C+ and D segmenters sold in India.
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Old 30th August 2009, 21:57   #7
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After fastening the seatbelt, grab the belt and jerk (quite forcefully) it forward. if it locks, your belt is fine.

cheers
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Old 30th August 2009, 23:27   #8
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Well i think pretensioners ONLY work when the accelerometers detect a crash. That is also the time when the airbags get deployed. Airbags open with great velocity, and it is one of the jobs of the pretensioners to ensure the seat belt tightens so that the driver DOES NOT hit the airbags with that much velocity. You cannot check pre tensioner functioning in regular circumstances. Pretensioners only come as a life saving tool in case of a collision.
Also, I guess all the cars which have airbags installed also have seat belt pretensioners installed.
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Old 31st August 2009, 00:01   #9
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Quote:
Originally Posted by deky View Post
I give the seat belt a small tug just to check if the seat belt is working/ fixed properly.
While driving, on and off I keep moving my torso forward just to check if the seat belt is holding my upper body back.
I would say you are being paranoid, you don't have to check so often. Relax and enjoy the drive, life, whatever. Seat belt is a simple mechanical device based on centrifugal force- no sensor, no electronic signal, etc, etc. Like others have already said, a quick tug and lock will tell you that it is working as intended.
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Old 31st August 2009, 10:11   #10
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I have noticed that the belts hold me tight when I accelerate too fast around a corner. Has anybody else noticed this?
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Old 31st August 2009, 10:31   #11
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yeah, me too felt it. Not when accelerating, but under heavy braking.
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Old 31st August 2009, 10:40   #12
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Thank you for replying and giving your inputs.

Most of you guys have suggested to give it a "fast tug" forward and see if it gets stuck. But as already mentioned in the first post, on giving it a tug it does gets stuck

But when i jerk my upper body forward (towards the steering wheel, stimulating an accident like situation) the seat belt does not hold my upper torso back.

Can you guys check that in your car and reply if it happens in your car seat belts too? If it does, then is the seat belt faulty? Or how else can we check? Is hand tugging the only way to check the seat belts?
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Old 31st August 2009, 11:08   #13
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Quote:
Originally Posted by Matt View Post
yeah, me too felt it. Not when accelerating, but under heavy braking.
Exactly. Normally the seat belt allow me to move up to steering wheel. Last year in Mumbai when I was cruising at 60-70 on a flyover, a WagonR in front of me about 15-25 ft suddenly stopped in the right most lane. I had to break madly and at that point one of my friends sitting on the rear seat came forward but as he was aware whats happening could control his movement. The seat belts did not allow me to move even by couple of inches and I could handle the car quite well. I stopped almost couple of feet before that WagonR. After that I always ask people at back seat to wear seatbelt.
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Old 31st August 2009, 11:16   #14
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Quote:
deky : But when i jerk my upper body forward (towards the steering wheel, stimulating an accident like situation) the seat belt does not hold my upper torso back.
@Deky, that is because when you push your body forward, you are not pushing it fast enough for the pre-tensioner to work.

See, pushing a finger (like when you test) is easier & faster than pushing your entire torso forward. You may think you are pushing your torso fast enought, but you are not.

Also, even if the pre-tensioner does not work, the seat belt will still do it's job. The pre-tensioner, like has already been said here, is to stop you well before you reach the inflated air-bag (as will happen in an actual situation when the airbag is deployed).

Stop thinking about this, and focus on the road.
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Old 31st August 2009, 11:22   #15
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question. How to know if your airbags will deploy?
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