Half cage discussion

[MRzcp]

Hi guys, I recently stumbled on a thread that mentioned having fixed back seats w/out any sort of roll bar was dangerous due to the fact that the seats will not lay flat or collapse in the event of a rollover. I take my M3 to the track once per quarter and still drive it on the weekends, so a full cage is not an option. Does anyone have any input on the validity of this claim and whether the factory chassis provides adequate protection as is? I am interested in installing a half cage if it will offer greater protection, but am wondering if anyone has seen how effective they are.

[derbo]

I think the reason you stated is not correct. No way even factory seats are designed to collapse or lay flat in a rollover. The idea is to keep your body as close to the center of the car while in a rollover as most injuries are due to the body hitting things outside the window.

Have a look at this video where this man from HMS talks about here in the quickfit pro video and the myths of the internet forums. Check about 5:22 in the video

Fixed back seats also typically do not have access to the 3pt buckle properly. This usually means your buckle goes over the bolsters but leaves a gap between your hip. This is also a dangerous situation as it is not holding you in properly even with the 3pt. There are a few seats here and there that do satisfy this requirement so do some research on that.

Another thing is, you also remove the side airbags from this car without adding anything back for the removed side protection. That is a risk you should be aware of.

With a roll bar/half cage, on the street, the cage is now semi-liable for your head injury without a helmet. BMW M4 GTS has padded roll cages from the factory to be able to sell in the USA.


I personally went with a quickfit pro + HANS device with stock seat to hold me better. It should be more than enough and also DOT legal

[MRzcp]

Originally Posted by derbo

I think the reason you stated is not correct. No way even factory seats are designed to collapse or lay flat in a rollover. The idea is to keep your body as close to the center of the car while in a rollover as most injuries are due to the body hitting things outside the window.

Have a look at this video where this man from HMS talks about here in the quickfit pro video and the myths of the internet forums.

Fixed back seats also typically do not have access to the 3pt buckle properly. This usually means your buckle goes over the bolsters but leaves a gap between your hip. This is also a dangerous situation as it is not holding you in properly even with the 3pt. There are a few seats here and there that do satisfy this requirement so do some research on that.

Another thing is, you also remove the side airbags from this car without adding anything back for the removed side protection. That is a risk you should be aware of.

With a roll bar/half cage, on the street, the cage is now semi-liable for your head injury without a helmet. BMW M4 GTS has padded roll cages from the factory to be able to sell in the USA.


I personally went with a quickfit pro + HANS device with stock seat to hold me better. It should be more than enough and also DOT legal

This is very valuable information, thank you for your reponse!

[macdude357]

I was looking into this myself a while back. I was using the Quickfit Pros with my stock seats and didn't like how high the "buckle" ended up when I tightened down the shoulder harnesses. No matter how tight I made the lap belt, the buckle would ride above my pelvic bone. I ended up going with the Cobra Nogaro seats which have a slot for a sub-strap. The seats are very supportive and are low enough across the lap to allow for the stock lap belt to fit properly. I ran that setup for while and it worked well. I decided to take this one step farther and bought the harness bar from BK Auto and replaced the Quickfits with the Schroth Profi II belts which work like the Quickfits (ie have the ASM feature) but are made to connect to a harness bar. The extra play that the ASM harness gives you would mean I'm less likely to be stuck in the upright position in the case of a rollover. You lose the side airbags though. I will eventually move to a full cage so I didn't want a half cage only to have to replace it with a full cage.

[roastbeef]

i've thought about this for a while now. i've seen a few wrecked e90's and e92's that have rolled over and cabin intrusion appeared to be very minimal. cars are pretty rigid these days and crush risk from a rollover seems to be pretty minimal. major injuries seem to be from limbs flopping around or conking your head on things.
conking your head on a roll cage seems to be the greater danger. if you watch slow motion crash tests where the dummies flop around with oem three point belts in different kinds of impacts, you can imagine how a rigid cage in the cabin could become a factor... i'd theorize fixed back seats aren't a part of that danger.

[derbo]

Originally Posted by roastbeef

i've thought about this for a while now. i've seen a few wrecked e90's and e92's that have rolled over and cabin intrusion appeared to be very minimal. cars are pretty rigid these days and crush risk from a rollover seems to be pretty minimal. major injuries seem to be from limbs flopping around or conking your head on things.
conking your head on a roll cage seems to be the greater danger. if you watch slow motion crash tests where the dummies flop around with oem three point belts in different kinds of impacts, you can imagine how a rigid cage in the cabin could become a factor... i'd theorize fixed back seats aren't a part of that danger.

I think fixed back seats are fine if the following is possible

• if using 3pt, 3pt belt buckle will allow the seatbelt to be flat on your body and not leave a gap.
• if using a 4pt Harness, it should be an ASM model, and you should probably be using a head and neck restraint.

I like macdude357 's setup with a Schroth 4 ASM + Harness bar but I do know a few clubs here and there do not allow 4pt harness unless its quick fits for your car specifically and usually won't allow multi-point harness without cage. That can be a problem depending on region.

You will lose a bit of side protection with the lost of the side airbag though..and that is something to consider.

[b4hand]

Originally Posted by MRzcp

Hi guys, I recently stumbled on a thread that mentioned having fixed back seats w/out any sort of roll bar was dangerous due to the fact that the seats will not lay flat or collapse in the event of a rollover. I take my M3 to the track once per quarter and still drive it on the weekends, so a full cage is not an option. Does anyone have any input on the validity of this claim and whether the factory chassis provides adequate protection as is? I am interested in installing a half cage if it will offer greater protection, but am wondering if anyone has seen how effective they are.

You have to think of the safety systems as just that, a system. If you get a half-cage with stock seats, you aren't benefiting from anything imo. So you need at least bucket seats. If you get bucket seats you need to get a proper set of harnesses. Quick Fit Pro's are only authorized to work with 1 aftermarket seat.

I was recently debating about going with quick-fit pro's but I HATE the stock seat for track driving (I'm a bit thicc). The solution was a half-cage and fixed seats. I LOVE driving the car on track now. It feels amazing and I would recommend it to anyone.

I know Kelse92 has a harness bar and bucket seats but idk if her car is a daily. So does SYT_Shadow but he has like 8 cars.

[SYT_Shadow]

I run fixed back seats in two cars, in both cases with the BK harness bar. It's an excellent solution and you can remove the harness bar easily to store tires in the back or to allow humans in there.

I have zero concerns about this being more dangerous than stock. HMS has a nice video linked above and in the BK bar review in my signature I link to a whitepaper that explains you are indeed better off with proper seats and harnesses without a cage/half cage than on your OEM seats.

[dparm]

b4hand hit the nail on the head. This all comes back to the idea of a safety SYSTEM. The car is designed to protect occupants if the factory seat, factory seat belt, air bags, etc. all work in tandem. As soon as you change one component, all bets are off...meaning you need to commit to a new safety SYSTEM (cage, halo, 6-points, etc).

That being said, rollovers in HPDE are exceedingly rare, as others have said on this forum before. I think I've maybe seen one or two in 10+ years of doing this stuff.

[Kelse92]

Originally Posted by b4hand

You have to think of the safety systems as just that, a system. If you get a half-cage with stock seats, you aren't benefiting from anything imo. So you need at least bucket seats. If you get bucket seats you need to get a proper set of harnesses. Quick Fit Pro's are only authorized to work with 1 aftermarket seat.

I was recently debating about going with quick-fit pro's but I HATE the stock seat for track driving (I'm a bit thicc). The solution was a half-cage and fixed seats. I LOVE driving the car on track now. It feels amazing and I would recommend it to anyone.

I know Kelse92 has a harness bar and bucket seats but idk if her car is a daily. So does SYT_Shadow but he has like 8 cars.

I have seats, no harness bar, and I use a 3-point belt. I have Quick fit Pro's but I only use them with the seat at autocross, not at the track. I do daily my car still 50% of the time between the M3 and X3 which is actually my sister's but she's living out of state right now so I stole it

[derbo]

Originally Posted by SYT_Shadow

I run fixed back seats in two cars, in both cases with the BK harness bar. It's an excellent solution and you can remove the harness bar easily to store tires in the back or to allow humans in there.

I have zero concerns about this being more dangerous than stock. HMS has a nice video linked above and in the BK bar review in my signature I link to a whitepaper that explains you are indeed better off with proper seats and harnesses without a cage/half cage than on your OEM seats.

The link to the whitepaper now redirects to the main page. I assume it is dead now. You wouldn't have a copy of it? I love to read it.

[SYT_Shadow]

Originally Posted by derbo

The link to the whitepaper now redirects to the main page. I assume it is dead now. You wouldn't have a copy of it? I love to read it.

Unfortunately it's gone, but here are the important bits.

One would think that this would settle the conversation once and for all about doing 6 points and a harness bar.
I want to meet the forum supermans who can 'duck' from the roof at 10g to 35g during a rollover.

I sleep very well at night with my option of the BK bar, race seats and 6 points for track use

[DRLane]

Welp, my sparco buckets can't accommodate the factory belt receiver and I'm stuck with that lap seatbelt gap. Maybe I can reuse the rear seat receivers up front as they're soft and could thread through the seat? Anyhow tried this? Factory airbags (curtain and fronts) are at least retained.

Otherwise, I'll just remove the factory seat belts and use 6 pt full time. Car doesn't really go anywhere but to and from track, plus the occasional drive or golf course.

[SYT_Shadow]

Originally Posted by DRLane

Welp, my sparco buckets can't accommodate the factory belt receiver and I'm stuck with that lap seatbelt gap. Maybe I can reuse the rear seat receivers up front as they're soft and could thread through the seat? Anyhow tried this? Factory airbags (curtain and fronts) are at least retained.

Otherwise, I'll just remove the factory seat belts and use 6 pt full time. Car doesn't really go anywhere but to and from track, plus the occasional drive or golf course.

Some do thread the buckle through the seat and use the floppy seat buckles to achieve that.

I would not run a 6 point without a Hans device, which you can't do on the street. Without wearing a helmet it's possible a 6 point is not a death sentence, but I would still not want to try it.

[DRLane]

Originally Posted by SYT_Shadow

Some do thread the buckle through the seat and use the floppy seat buckles to achieve that.

I would not run a 6 point without a Hans device, which you can't do on the street. Without wearing a helmet it's possible a 6 point is not a death sentence, but I would still not want to try it.

Fair. Guessing my head snapping forward wouldn't get the airbag relief like with a traditional 3 point.

[derbo]

Originally Posted by DRLane

Welp, my sparco buckets can't accommodate the factory belt receiver and I'm stuck with that lap seatbelt gap. Maybe I can reuse the rear seat receivers up front as they're soft and could thread through the seat? Anyhow tried this? Factory airbags (curtain and fronts) are at least retained.

Otherwise, I'll just remove the factory seat belts and use 6 pt full time. Car doesn't really go anywhere but to and from track, plus the occasional drive or golf course.

The factory front buckles also have charged tensioners that pull when an impact is detected. You might be able to get away with a seatbelt buckle extension to utilize the factory buckle? I'm not sure on how well the angle would be.



You can see factory buckets (seems to be non-US for all of these) has areas to allow the 3pt to be snug to the body.

[dparm]

Originally Posted by SYT_Shadow

Unfortunately it's gone, but here are the important bits.

I actually have the PDF file, though it's 86MB.

What bugs me about this presentation is how they say no HANS without a 5- or 6-point belt, but other parts of the site and documentation say a HANS can be used with a proper 4-point FIA belt. I'll keep using mine.

[SYT_Shadow]

Originally Posted by dparm

I actually have the PDF file, though it's 86MB.

What bugs me about this presentation is how they say no HANS without a 5- or 6-point belt, but other parts of the site and documentation say a HANS can be used with a proper 4-point FIA belt. I'll keep using mine.

Their own QFP is rated for the Hans device if I remember correctly

[dparm]

Originally Posted by SYT_Shadow

Their own QFP is rated for the Hans device if I remember correctly

Exactly, that's what I don't understand. Maybe just a typo. I don't see how a HANS would not work with the 4-point.

[derbo]

Originally Posted by dparm

Exactly, that's what I don't understand. Maybe just a typo. I don't see how a HANS would not work with the 4-point.

I think the only concern with a 4pt is submarining if there is no ASM feature on the harness.

[SYT_Shadow]

Originally Posted by derbo

I think the only concern with a 4pt is submarining if there is no ASM feature on the harness.

That is likely it. Schroth/HMS really doesn't like 4 points that don't have ASM

[rhyary]

Originally Posted by SYT_Shadow

That is likely it. Schroth/HMS really doesn't like 4 points that don't have ASM

what is ASM?