Seatbelt over-tightens itself

[cyberman]

My wife complains that as we ride, her seatbelt gets tighter and tighter. I've addressed the problem with a device that clamps on belt adjacent the seat belt guide and that holds it in place. Does anyone know of a more elegant solution to this problem?

[zellamay]

I don't think it's a "problem". The seatbelt is supposed to be tight. I usually pull it as tight as it will go with my arm-force. A device that keeps the seat belt loose would seem dangerous to me. Maybe it's about location across her body. My wife is very small and sometimes complains about seatbelts.

[khammack]

My seat-belt does not get tight unless you pull on the rather fast or the car stops quickly. During normal driving the belt should not lockup and it should be easy to pull out. It sounds like your seat-belt tensioner may be defective.

[BimmerBreaker]

The seatbelt should be "loose" in so much as it should allow free movement (such as leaning forward). In an accident, the seatbelt tensioner has a pyrotechnic device which will activate and tighten the seatbelt to keep your body tight to the seat

One of my roadsters recently started to develop this issue but I haven't looked into it too much yet. It is happening very intermittently, but starting to occur at a more regular frequency. It also occasionally "locks" while pulling it out to latch it, so at least in my case, it is surely an issue with the seatbelt mechanism itself, not the latch mechanism. I'm going to start with pulling the belts all the way out and then cleaning the belt but I don't suspect that will fix it

[cyberman]

The seatbelt should be "loose" in so much as it should allow free movement (such as leaning forward). In an accident, the seatbelt tensioner has a pyrotechnic device which will activate and tighten the seatbelt to keep your body tight to the seat

One of my roadsters recently started to develop this issue but I haven't looked into it too much yet. It is happening very intermittently, but starting to occur at a more regular frequency. It also occasionally "locks" while pulling it out to latch it, so at least in my case, it is surely an issue with the seatbelt mechanism itself, not the latch mechanism. I'm going to start with pulling the belts all the way out and then cleaning the belt but I don't suspect that will fix it

My symptoms exactly. After decades of driving with seatbelts we know how they should behave. The should allow one to lean forward to, for example, get things out of the glovebox. This thing not only locks, but it continues to tighten as we drive making her feel like a boa constrictor is trying to kill her. It must be a common problem across many car models as Amazon has a large number of locking devices such as the one we're using:

seatbelt extender.jpg

[zellamay]

I've had mine "lock" occasionally when I lean forward fast. All I do is sit upright, then lean forward a little slower than before. So far, that works. ..... I would fix whatever the problem is before I would use one of those "Amazon" devices. I always want the belt to return to a tight position after I return to the sitting-upright position.

[Hoyt Clagwell]

I once drove school bus and my bus had this issue. Every time I exhaled the belt tightened another notch like a boa constrictor. If I needed to be paying a lot of attention to the driving conditions, it could get down right painful and be difficult to pull loose. The only way to pull it loose was to grab it and exhale some more. Sometimes, I just didn't have any lung capacity left.

I used a regular spring clam to accomplish the same thing as one of those clamps. I wouldn't recommend it though as the seat belt is supposed to stay reasonably tight against your body but only lock up in the case of sudden inertia as in a collision. If there is any gap between the belt and you, you will slam against the belt and cause bruises and lacerations if not worse.
I would recommend fixing it properly. I don't know much about the mechanism but it may just need cleaning and lubing. On the other hand, as Cyberman has said before, "safety, schmafety".

[khammack]

Here is a link to the diagram in realoem.com (I guessed at the engine size, so you may need to do another lookup using the correct engine, but I think they are all about the same).
https://www.realoem.com/bmw/enUS/sho...diagId=72_0080

It should give you an idea about where things are and how you may be able to clean and lube the retractor to fix your issue.

[zellamay]

And, there is maintenance. Washing the belt will help it operate much smoother and easier. Here's a thread discussing it: https://www.bimmerforums.com/forum/s...your-seat-belt

[z3forlife]

I wonder if this is a side effect of your new seat cushions. Thicker cushion would compress more causing the ratchet on the retractor to tighten. I don’t think cleaning is going to make much difference with this specific problem. The only other thing would be a sticking inertia latch.

[cyberman]

I wonder if this is a side effect of your new seat cushions. Thicker cushion would compress more causing the ratchet on the retractor to tighten. I don’t think cleaning is going to make much difference with this specific problem. The only other thing would be a sticking inertia latch.

This has been happening since before I put in cushions, about two years now since I purchased the car and it doesn't happen on the driver's side.

And, there is maintenance. Washing the belt will help it operate much smoother and easier.

Already did that, but I was under the impression that this helps at times with smooth retraction, not locking. In our case, one must slowly and steadily pull the seat belt out or it will lock. Once it locks, usually letting it retract a bit will unlock it. But sometimes it then won't pull out until we let it retract completely.

Here is a link to the diagram in realoem.com (I guessed at the engine size, so you may need to do another lookup using the correct engine, but I think they are all about the same).
https://www.realoem.com/bmw/enUS/sho...diagId=72_0080

It should give you an idea about where things are and how you may be able to clean and lube the retractor to fix your issue.

Thanks, but this work is what I feared all along. It's complicated by my aftermarket rollbar (with speakers installed) and the risk is that I won't be able to fix the issue.