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      04-16-2014, 06:11 AM   #1
03///m3
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Anyway to lock chest strap?

Is there anyway or device that will lock the chest belt on the stock 3 point restraint system? I have a CG lock that will lock the lap belt and it really helps however if i were to lock the lap and chest belt it would be much better.

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      04-16-2014, 06:38 AM   #2
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No. And for safety reasons you wouldn't want to. One of the reasons a 3-point OEM belt works during a roll over (or really works at all) is it allows your body to move. In a forward impact you can pitch forward and decelerate and in a roll over you can roll out of the way if/when the b-pillars buckle.

Locking the chest strap is basically the same as having a 5/6-point harness as far as deceleration and roll-over but without the benefit of extra restraint, the ability to run a HANS, or a roll cage.

I've run a CG lock and felt it gave almost as much retention as the Schroth Quick-Fits. Would a 5/6-point be better? Sure. But the CG Lock is pretty darn good for what it costs and the fact that you give up none of the safety built into the OEM restraint system.
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      04-16-2014, 07:37 AM   #3
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Quote:
Originally Posted by dmw16 View Post
No. And for safety reasons you wouldn't want to. One of the reasons a 3-point OEM belt works during a roll over (or really works at all) is it allows your body to move. In a forward impact you can pitch forward and decelerate and in a roll over you can roll out of the way if/when the b-pillars buckle.

Locking the chest strap is basically the same as having a 5/6-point harness as far as deceleration and roll-over but without the benefit of extra restraint, the ability to run a HANS, or a roll cage.

I've run a CG lock and felt it gave almost as much retention as the Schroth Quick-Fits. Would a 5/6-point be better? Sure. But the CG Lock is pretty darn good for what it costs and the fact that you give up none of the safety built into the OEM restraint system.
I pretty sure this is bollocks. The 3-point system has pretensioners and a pyrotechnic charge to lock you into your seat and sit you bolt upright in a crash. This creates a predictable position for the other safety features to work with.

There is also a fantasy that in a roll you have the time and strength to adjust your position while being spun violently under quite a lot of G-force. Modern cars are so heavy due in part to the required strenghtening of the canopy to maintain room during a roll over - in particular the A-pillars are particularly strong as these take the brunt of flip. In older cars, there was not this same provision, and roofs would collapse, but there is still a lot of "lore" carried over from the older designs s (same thing with 3000 mile oil changes - the technology moves faster than the culture). In a pancake flip, you are pretty much screwed without a full cage.

To the OP, you can lock you belt by moving the seat back, tugging it hard to lock it, and then moving the seat forward to the desired tension across your chest. This works with a CG lock too. You can also put a twist in the belt too for added "locking". I added a Scroth Rallye 3 harness to my 2008 M3 for added stability, although the Quick-Fit systems and Rallye 4 systems are also available. When I installed, the M3 seat had not been granted a safety certificate that made it okay to to have downward angle restraints, they do now. The Rallye 3 goes straight back to use the rear seat shoulder anchor point.
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      04-16-2014, 08:07 AM   #4
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Quote:
Originally Posted by LiM3y View Post
I pretty sure this is bollocks. The 3-point system has pretensioners and a pyrotechnic charge to lock you into your seat and sit you bolt upright in a crash. This creates a predictable position for the other safety features to work with.

There is also a fantasy that in a roll you have the time and strength to adjust your position while being spun violently under quite a lot of G-force. Modern cars are so heavy due in part to the required strenghtening of the canopy to maintain room during a roll over - in particular the A-pillars are particularly strong as these take the brunt of flip. In older cars, there was not this same provision, and roofs would collapse, but there is still a lot of "lore" carried over from the older designs s (same thing with 3000 mile oil changes - the technology moves faster than the culture). In a pancake flip, you are pretty much screwed without a full cage.
It would take someone who actually engineers these systems to say for sure, but the pretensioners and the rest of the system still allows for some movement. That's part of the reason why a HANS is suggested in a race harness but you don't need one in a 3-point belt system.

As for the roll over. I wasn't suggesting you can adjust yourself with intent. What I was saying is that your body is free(ish) to flop forward and deflect as the roof displaces into the cabin. And yes, modern cars are heavy, but roofs don't cave as a matter of course. Most well engineered cars are designed to support 10x their weight with the roof of the car. Or so is a data point I've heard.

It's not really a point worth debating so people are free to disagree with me. But in general, it's my opinion based on at least some technical and engineering knowledge that the safety system is just that, a system. And messing with it in half-measures isn't a wise idea. If you need more restraint than a stock seat and a CG Lock can give you either get a deeper, more bolstered seat, or go full out. But at this point I'm rambling, so I'll stop.

OP, have you considered something like the Sporster CS seat if you need more side bolstering?
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      04-16-2014, 08:25 AM   #5
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Agree with LiM3y. The energy absorption during an incident occurs in the stretch of the belts. Look up video of race car crashes....even with tight 6 point harnesses the amount of the movement of the body is more than you would expect. My reply would have been nearly the same as LiM3y. Twisting the belt and locking the pretensioner in place is a good suggestion.
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      04-16-2014, 08:33 AM   #6
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All I could find on YouTube. I am searching for the factory roll over test film. It is out there, I remember seeing it.

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      04-16-2014, 10:20 AM   #7
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Quote:
Originally Posted by dmw16 View Post
No. And for safety reasons you wouldn't want to. One of the reasons a 3-point OEM belt works during a roll over (or really works at all) is it allows your body to move. In a forward impact you can pitch forward and decelerate and in a roll over you can roll out of the way if/when the b-pillars buckle.

Locking the chest strap is basically the same as having a 5/6-point harness as far as deceleration and roll-over but without the benefit of extra restraint, the ability to run a HANS, or a roll cage.

I've run a CG lock and felt it gave almost as much retention as the Schroth Quick-Fits. Would a 5/6-point be better? Sure. But the CG Lock is pretty darn good for what it costs and the fact that you give up none of the safety built into the OEM restraint system.

Sorry but that's wrong. As another user pointed out, in an impact with a sudden force, the OEM pretensioners fire and lock the 3 point belt.

Go to any junk yard and pull on the belts of cars that have been in accidents, they should all be locked. This is a good indicator whether someone was wearing their seatbelt as it will also lock against the B pillar if not in use.

The reason we don't drive locked down ala harnesses is for comfort/convience. But in the event of accidents, the belts fire, locking you into place.
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      04-16-2014, 11:05 AM   #8
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Quote:
Originally Posted by LiM3y View Post
I pretty sure this is bollocks. The 3-point system has pretensioners and a pyrotechnic charge to lock you into your seat and sit you bolt upright in a crash. This creates a predictable position for the other safety features to work with.

There is also a fantasy that in a roll you have the time and strength to adjust your position while being spun violently under quite a lot of G-force. Modern cars are so heavy due in part to the required strenghtening of the canopy to maintain room during a roll over - in particular the A-pillars are particularly strong as these take the brunt of flip. In older cars, there was not this same provision, and roofs would collapse, but there is still a lot of "lore" carried over from the older designs s (same thing with 3000 mile oil changes - the technology moves faster than the culture). In a pancake flip, you are pretty much screwed without a full cage.

To the OP, you can lock you belt by moving the seat back, tugging it hard to lock it, and then moving the seat forward to the desired tension across your chest. This works with a CG lock too. You can also put a twist in the belt too for added "locking". I added a Scroth Rallye 3 harness to my 2008 M3 for added stability, although the Quick-Fit systems and Rallye 4 systems are also available. When I installed, the M3 seat had not been granted a safety certificate that made it okay to to have downward angle restraints, they do now. The Rallye 3 goes straight back to use the rear seat shoulder anchor point.
Thanks for the suggestion. I will give that a try. It would be great to be able to totally lock the 3 point system on track days.

And the reason i am currently not considering an aftermarket seat like the Recaro Sportster CS is that they don't have airbags (I know the BMW performance seats do but they are $5k) and are expensive for probably being only slightly more supportive than the stock seats with a CG lock. If i ever were to consider changing the seats would like to get fixed back shells like a Pole position but i need to use the rear seats (i have a baby and another on the way) so that is out of the question.
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      04-16-2014, 04:43 PM   #9
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Quote:
Originally Posted by 03///m3 View Post
Quote:
Originally Posted by LiM3y View Post
I pretty sure this is bollocks. The 3-point system has pretensioners and a pyrotechnic charge to lock you into your seat and sit you bolt upright in a crash. This creates a predictable position for the other safety features to work with.

There is also a fantasy that in a roll you have the time and strength to adjust your position while being spun violently under quite a lot of G-force. Modern cars are so heavy due in part to the required strenghtening of the canopy to maintain room during a roll over - in particular the A-pillars are particularly strong as these take the brunt of flip. In older cars, there was not this same provision, and roofs would collapse, but there is still a lot of "lore" carried over from the older designs s (same thing with 3000 mile oil changes - the technology moves faster than the culture). In a pancake flip, you are pretty much screwed without a full cage.

To the OP, you can lock you belt by moving the seat back, tugging it hard to lock it, and then moving the seat forward to the desired tension across your chest. This works with a CG lock too. You can also put a twist in the belt too for added "locking". I added a Scroth Rallye 3 harness to my 2008 M3 for added stability, although the Quick-Fit systems and Rallye 4 systems are also available. When I installed, the M3 seat had not been granted a safety certificate that made it okay to to have downward angle restraints, they do now. The Rallye 3 goes straight back to use the rear seat shoulder anchor point.
Thanks for the suggestion. I will give that a try. It would be great to be able to totally lock the 3 point system on track days.

And the reason i am currently not considering an aftermarket seat like the Recaro Sportster CS is that they don't have airbags (I know the BMW performance seats do but they are $5k) and are expensive for probably being only slightly more supportive than the stock seats with a CG lock. If i ever were to consider changing the seats would like to get fixed back shells like a Pole position but i need to use the rear seats (i have a baby and another on the way) so that is out of the question.
That's what I do too. I'm locked in nice & tight no matter how severe the car's slip angle gets. Stopped looking for Recaro's/harness thereafter.
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      04-16-2014, 08:29 PM   #10
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Locking the chest strap with CG Lock is similar to what pyro does at impact and does not impair the action of your body to fall to the right lowering your position to avoid vertical crush in a rollover scenario.
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