Seat belts in my 22’ wrangler do not lock when applying the brake

[CarRamRod25]

Dumb question but I’ve noticed the seatbelts in my 22’ wrangler do not lock when applying the brakes. To clarify, when driving and I rapidly apply the brakes, the seatbelts do not lock and allow full extension, they dont lock at all. I’m kind of fond of my face and would like to preserve it for as long as possible. Is this something common with Jeeps? Is there something I’m missing ?
thank you all in advanced.

 

[Heimkehr]

@CarRamRod25
Rick, have you given a brisk pull on the shoulder portion of the belt to determine if the seat belt only locks at a certain force threshold?

 

[Some Random Guy]

My ‘22 locks. It happens a lot to me at a certain part of my commute. I have a steep hill to climb to reach a rural highway with a stop at the top. I drive a manual, so I’m usually carrying speed until I clutch in and try to come to a stop at the right spot to avoid starting in 1st twice. The seatbelt lock makes it hard to crane my head around campaign signs posted on the corner to see if someone is coming at 65+ mph.

 

[jeepoch]

@CarRamRod25,

Rick,

The seat belts are designed to lock with a high enough deceleration force. If the jerk vectors are high enough the safety systems will engage. The seat belts way before the air bags.

The engineers are stuck with trying to prevent annoying lock conditions, such as preventing @Some Random Guy from craning his neck to look around campaign signs while trying to blow by them. Sir you have my sympathy.

Jay

 

[Some Random Guy]

I’ll take it in exchange for keeping my face out of the steering wheel when the airbag goes off. I just have to relax and then lean forward again after coming to a stop.

@CarRamRod25,

Rick,

The seat belts are designed to lock with a high enough deceleration force. If the jerk vectors are high enough the safety systems will engage. The seat belts way before the air bags.

The engineers are stuck with trying to prevent annoying lock conditions, such as preventing @Some Random Guy from craning his neck to look around campaign signs while trying to blow by them. Sir you have my sympathy.

Jay

 

[Heimkehr]

"Jerk vector".

I'm adding that one to the lexicon.

 

[JayJay]

"Jerk vector".

I'm adding that one to the lexicon.

I think that I've noticed a few of those on the forum recently.

 

[Heimkehr]

I think that I've noticed a few of those on the forum recently.

I'd be fibbing if I said I didn't think the same thing.

No worries. Diversity of opinion can be useful at times.

 

[CarRamRod25]

@CarRamRod25
Rick, have you given a brisk pull on the shoulder portion of the belt to determine if the seat belt only locks at a certain force threshold?

Yep. I even had my wife driving, accelerated, then quick firm braking, and then a 25 mph to firm slam on the brakes and nothing. The rear ones lock for sure.

 

[Some Random Guy]

Yep. I even had my wife driving, accelerated, then quick firm braking, and then a 25 mph to firm slam on the brakes and nothing. The rear ones lock for sure.

Seems like a dealer trip for a safety issue. If they’re not locking their only function left is ticket avoidance.

 

[jeepoch]

For reference in physics, the 1st derivative of a change in position (x) with respect to time dx/dt = velocity (v). The 2nd derivative, the change in velocity over time dv/dt = acceleration (a). The 3rd derivative, the change in acceleration over time da/dt = jerk (j).

Said in another way, velocity is the change in position, acceleration is the change of velocity and the jerk is a change in acceleration over time.

Therefore a jerk is something that changes force vectors of a moving object in relation to how quickly it's either accelerating (or decelerating). The faster the change in acceleration over a fixed span of time, the higher the resultant jerk.

Decelerate slowly (low jerk), you hardly sense it. Decelerate quicker, such as locking the breaks and skidding the tires (moderate jerk) you'll feel the push on your seat belts. Decelerate very quick, like hitting a tree (high jerk) you'll certainly be punished by the airbags. Hoping of course you survive.

Another name for a high jerk on your being is called 'blunt force trauma'.

I suppose you can call a jerk on this thread, a blunt force being. I've been called worse.

Jay or just (j) for short.
Coincidence???

 

[CarRamRod25]

For reference in physics, the 1st derivative of a change in position (x) with respect to time dx/dt = velocity (v). The 2nd derivative, the change in velocity over time dv/dt = acceleration (a). The 3rd derivative, the change in acceleration over time da/dt = jerk (j).

Said in another way, velocity is the change in position, acceleration is the change of velocity and the jerk is a change in acceleration over time.

Therefore a jerk is something that changes force vectors of a moving object in relation to how quickly it's either accelerating (or decelerating). The faster the change in acceleration over a fixed span of time, the higher the resultant jerk.

Decelerate slowly (low jerk), you hardly sense it. Decelerate quicker, such as locking the breaks and skidding the tires (moderate jerk) you'll feel the push on your seat belts. Decelerate very quick, like hitting a tree (high jerk) you'll certainly be punished by the airbags. Hoping of course you survive.

Another name for a high jerk on your being is called 'blunt force trauma'.

I suppose you can call a jerk on this thread, a blunt force being. I've been called worse.

Jay or just (j) for short.
Coincidence???

Front Seat belts do not lock. Accelerate to rapid deceleration or in motion to rapid stop.
Thank you for making me think, I have now forgotten what my wedding day was like.

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