Bolt-on Rollcage for E92 M3 - Anyone?

[syncros]

Hello,
Does anyone in this forum heard of a bolt-on rollcage for a E92 M3? I've seen this kind of cage in many E46 but none on in our car.

Its an option that I may consider for the end of the season or next year in order to install a 6 point harness in my car when tracking the car with a race seat.

Thanks, Vince

[lucid]

I considered this some time ago and concluded that it is a bad idea. There seems to be no point in "bolting on" a roll cage without welding plates to the chassis to reinforce the bolt locations. Otherwise, if you really roll the car (not a soft roll), the tubes will most likely go through the chassis or deform it significantly , and the "cage" will not function as a "roll" cage. Since your harness would be attached to it, you might be pulled along as well. One can argue that one can find bolt-on locations in the chassis that are strong enough, but I have a hard time buying that unless I see evidence/validation (in the form of a proper FEA sim or a real-world test) and would not take someone's "opinion" as proof--regardless of who he is. I saw an E46 a few months ago at the track with such a setup, and when I asked the owner why he thought it was safe, he said it bolts to where the seatbelts are attached in the chassis. He clearly had not thought it through because the max load a seatbelt can experience in a roll-over is obviously much smaller than what a roll cage would. Anyway, if what you are after is a harness bar, why not have an harness bar installed instead of a roll cage that won't really function without some serious welding/chassis modification?

[sparkyg]

+1 Lucid.

Roll cage is thre to protect the occupant and the only real roll cage is a custome mage weld-in style.

Speaking of cages, check out this one on Rogues site. So killer.

[Gearhead999s]

John from Raven Performance just built an E92 M3 for track days for a customer that has an extremly nice chrome-moly cage in it.A friends wife has a bolt in harness bar & roll bar in her E46 M3 that was also done by John.He also did a custom seat mount to install a proper race seat in her E46.This is a very good idea as you can run a Hans with no comprimise on the belt mounting.If there a lot of track days in the E92 in the future,I will probally go this direction.

http://www.ravenperformance.com/chassis

http://www.ravenperformance.com/

[Gearhead999s]

More here.

http://www.m3forum.net/m3forum/showthread.php?t=254359

[swamp2]

Originally Posted by lucid

I considered this some time ago and concluded that it is a bad idea.
...
a roll cage that won't really function without some serious welding/chassis modification?

I recall discussing this with you by PM. We certainly can not say a bolt in roll cage WILL function "perfectly" as designed/as intended, however it is also premature and unfounded to say that it IS a bad idea and WON'T function. I suspect that a properly designed bolt in roll cage on a street car will offer substantially improved protection under most crushing/compression types of loads. Shear loads might be a case where things could get ugly if the cage completely sheared from the vehicle. However, even under shearing you would likely get more protection with than without. I absolutely agree that FEA could answer the question quite well. However, careful considerations of the various load cases would be a key part of such an analysis.

[lucid]

Originally Posted by swamp2

I recall discussing this with you by PM. We certainly can not say a bolt in roll cage WILL function "perfectly" as designed/as intended, however it is also premature and unfounded to say that it IS a bad idea and WON'T function. I suspect that a properly designed bolt in roll cage on a street car will offer substantially improved protection under most crushing/compression types of loads. Shear loads might be a case where things could get ugly if the cage completely sheared from the vehicle. However, even under shearing you would likely get more protection with than without. I absolutely agree that FEA could answer the question quite well. However, careful considerations of the various load cases would be a key part of such an analysis.

Yes, I discussed this with you and several other people, including manufacturers, when I was trying to find ways of making things safer on the track. Implementing this type of modification IS indeed a bad idea unless it has been proven to be functioning properly because the risk associated with it not functioning properly is simply too high (the thing that is supposed to protect you can kill you). And I am not aware of any bolt on cage manufacturer providing ANY type of meaningful analysis or test result showing that its product really functions. I hear/read a lot of, "we've been doing this for years, so we know what we are doing..." I couldn't locate any real evidence, and I am therefore saying moving forward with it IS a bad idea. If someone provides the necessary evidence, it wouldn't be a bad idea. That simple.

You can bolt various things into the cabin, and sure, they can increase the structural integrity of the cabin even if they are bound to fail. That's not the bottom line though. You will be strapped to the cage. If the cage deflects significantly, it will pull you along with it, and you can be crushed against your seat, against the cage, etc. I wouldn't want to be strapped/stuck to a structural element that has sheared off from its attachment point, and is continuing to deform under some kind of load.

And if you were to quote/consider my entire post, what I mean by the cage "really functioning"--the language I used--would become clearer as opposed to it functioning in an uncertain manner.

[syncros]

Excellent feedback guys. Until someone demonstrate that this is safer then without one, I won't consider it. What surprise me is that Raven told me that they could make one for my car and that they didn't believe it would be so different than what I saw in a E46 in the same car as Gearhead999s mentionned above.

[lucid]

Originally Posted by syncros

Excellent feedback guys. Until someone demonstrate that this is safer then without one, I won't consider it. What surprise me is that Raven told me that they could make one for my car and that they didn't believe it would be so different than what I saw in a E46 in the same car as Gearhead999s mentionned above.

When I approached a reputable shop in the area that does a lot of harness/belt/cage work, they told me they wouldn't even consider bolting anything to the chassis without welding plates in first. So, again, different shops/manufacturers give you different answers. I am curios about how some shops say you don't even need to drill new holes, and they will use existing holes, and what their justification is. As far as I know, BMW has not designed any attachment/mounting points/holes into the chassis for this kind of modification that can cope with high impact roll-over loads. It is probably a different story when you look at a car like a GT3 though. I believe Porsche will actually sell you a roll cage that bolts on? But, then they must have done the necessary analysis and designed that into the chassis...

[Gearhead999s]

Originally Posted by lucid

When I approached a reputable shop in the area that does a lot of harness/belt/cage work, they told me they wouldn't even consider bolting anything to the chassis without welding plates in first. So, again, different shops/manufacturers give you different answers. I am curios about how some shops say you don't even need to drill new holes, and they will use existing holes, and what their justification is. As far as I know, BMW has not designed any attachment/mounting points/holes into the chassis for this kind of modification that can cope with high impact roll-over loads. It is probably a different story when you look at a car like a GT3 though. I believe Porsche will actually sell you a roll cage that bolts on? But, then they must have done the necessary analysis and designed that into the chassis...

I have lots of experiance with bolt in cages and they are not the way to go.Back in the 80's in showroom stock class's the cages had to be bolted in with a very small foot plate area(4"x4"),not welded as that was considered to be chassis reinforcement not a safety improvement by the rules.We saw lots of cars that were destroyed with the feet of the cages pushed through the floor.fortunatly the rules changed in the 90's and we were allowed to have proper welded in cages that would actually save the car & driver in the case of a heavy roll over.A proper cage will also contribute to a much better handling car as the movement will be in the suspension not in the chassis.The E92 in the pictures is a totally integrated welded in system that would work very well if ever used in anger.This is part of the reason that I might just just go back to a full caged racecar for lapping so I can take full advantage of all the modern safety advancements that now available for our protection.
For the occasional trackday the harness bar setup is probally not a bad way to go as it at least allows you to use a proper harness setup with a Hans device,but contributes nothing to helping to save the Tub in case of a major incident.I know my car will turn times in street trim at Mosport that would have qualified mid pack in a mid 70's Trans Am race.That is real quick a car with only street safety gear!Just something to think about.

[von_zoom]

I believe Porsche will actually sell you a roll cage that bolts on? But, then they must have done the necessary analysis and designed that into the chassis...

....or have a nice professionally written legal release that goes along with it.
vz

[Gearhead999s]

Originally Posted by von_zoom

....or have a nice professionally written legal release that goes along with it.
vz

Not in North American with nobody wanting to take responsibility for their actions

[lucid]

Originally Posted by Gearhead999s

Back in the 80's in showroom stock class's the cages had to be bolted in with a very small foot plate area(4"x4"),not welded as that was considered to be chassis reinforcement not a safety improvement by the rules.We saw lots of cars that were destroyed with the feet of the cages pushed through the floor.

Yep. This would be my main concern...

Speaking of protection, I did order an R3 device last week. Hoping to start using it this weekend. Also hoping not to be in a position to write a product review for it.

[Gearhead999s]

Originally Posted by lucid

Yep. This would be my main concern...

Now that I remember we had problems with tech as we also had used the seat belt mounts to locate the main hoop which was bolted through and used much larger mounting feet than allowed by the rules.Once the cage was welded into that car it had a couple of huge hits that would have destroyed the car when the cage was a bolt in.

[syncros]

What are you talking about exactly when you refer to "harness bar setup"?
Is this an option that can be added to a car without any modifications?
Tell me more please.

Thanks again,

[Gearhead999s]

Originally Posted by syncros

What are you talking about exactly when you refer to "harness bar setup"?
Is this an option that can be added to a car without any modifications?
Tell me more please.

Thanks again,

I would consider this to be a harness bar but it does offer some roll over protection but does nothing to stiffen the chassis.



http://www.ravenperformance.com/rollbars-2

[swamp2]

Originally Posted by lucid

Yes, I discussed this with you and several other people, including manufacturers, when I was trying to find ways of making things safer on the track. Implementing this type of modification IS indeed a bad idea unless it has been proven to be functioning properly because the risk associated with it not functioning properly is simply too high (the thing that is supposed to protect you can kill you). And I am not aware of any bolt on cage manufacturer providing ANY type of meaningful analysis or test result showing that its product really functions. I hear/read a lot of, "we've been doing this for years, so we know what we are doing..." I couldn't locate any real evidence, and I am therefore saying moving forward with it IS a bad idea. If someone provides the necessary evidence, it wouldn't be a bad idea. That simple.

You can bolt various things into the cabin, and sure, they can increase the structural integrity of the cabin even if they are bound to fail. That's not the bottom line though. You will be strapped to the cage. If the cage deflects significantly, it will pull you along with it, and you can be crushed against your seat, against the cage, etc. I wouldn't want to be strapped/stuck to a structural element that has sheared off from its attachment point, and is continuing to deform under some kind of load.

And if you were to quote/consider my entire post, what I mean by the cage "really functioning"--the language I used--would become clearer as opposed to it functioning in an uncertain manner.

We may have to agree to disagree.

Personally I would not put such an item into my car simply because I won't be tracking often and it moves the car too far away from a full street vehicle. It is a pretty major and irreversible modification (holes in carpet, trim, etc.). However, I just do not think it is fair nor accurate to say that because the system is not fully known/quantified/guaranteed then it IS a bad idea. I can appreciate the conservative point of view and agree that unknowns are bad. However, I'd place a strong bet that under virtually any roll over event no matter how the roll cage was mounted, you would be better off with it than without it. Of course with the very reasonable assumption that the cage itself is plenty strong enough. There are plenty of unknowns in a roll over without a cage as well, that doesn't mean you should never track nor drive your car on the street does it?

By the way, I thought my partial quoting accurately represented your opinion. I did not do it to misrepresent you.

[lucid]

Originally Posted by swamp2

There are plenty of unknowns in a roll over without a cage as well, that doesn't mean you should never track nor drive your car on the street does it?

The stock setup has been simulated in a million ways and some of the key scenarios have been tested/validated. A few bars that a guy bolts into your car in a shop has not been simulated or tested in any way. Which case has a higher degree of uncertainty built into it?

An interesting comparison would be to consider full on welded safety cages. I wonder what type of analysis those are based on? I must assume there is some of analysis. But more importantly, my guess is that people have simply learned a great deal from trial and error engineering in those cases. A race car rolling over in a race is not such an unlikely event whereas an enthusiast with a bolt-on partial cage rolling over in a HPDE is pretty rare.

[Gearhead999s]

Originally Posted by lucid

The stock setup has been simulated in a million ways and some of the key scenarios have been tested/validated. A few bars that a guy bolts into your car in a shop has not been simulated or tested in any way. Which case has a higher degree of uncertainty built into it?

An interesting comparison would be to consider full on welded safety cages. I wonder what type of analysis those are based on? I must assume there is some of analysis. But more importantly, my guess is that people have simply learned a great deal from trial and error engineering in those cases. A race car rolling over in a race is not such an unlikely event whereas an enthusiast with a bolt-on partial cage rolling over in a HPDE is pretty rare.

Most of the cages that are built for people of our level are copies of what has been used in factory race cars and those have certianly been analized & tested to death in most of the situations that we would ever encounter.I know that largest manufacture of roll cages in this area has a engineer on staff and I have certianly seen quite a few of their products used in anger with good results over the years.A cage has no place in a street driven car as you would need to wear a helmet in order to have the same level of head safety as you would in a stock M3 with airbags.Contacting a roll bar(even padded)with an unprotected head is not a very good thing.

[Ryan239]

Originally Posted by lucid

The stock setup has been simulated in a million ways and some of the key scenarios have been tested/validated. A few bars that a guy bolts into your car in a shop has not been simulated or tested in any way. Which case has a higher degree of uncertainty built into it?

An interesting comparison would be to consider full on welded safety cages. I wonder what type of analysis those are based on? I must assume there is some of analysis. But more importantly, my guess is that people have simply learned a great deal from trial and error engineering in those cases. A race car rolling over in a race is not such an unlikely event whereas an enthusiast with a bolt-on partial cage rolling over in a HPDE is pretty rare.

Attend more events and you'll see it happen; it's unfortunate but it's not uncommon.

I think having welded plates isn't a bad idea when using a bolt-in bar, as I have seen where in a rollover the main hoop did push through the floor of a vehicle, but I don't think not having them makes you any less safe than you would be without any sort of rollbar. I'd still take a bolted in (only) roll bar over no roll bar any day of the week.

A roll bar isn't only going to help you in a rollover situation, either. A side impact, depending on where you are hit, and a rear impact (also depending on where you are hit) are both incidents that can and do happen at the track. Having the additional protection at the 'B' pillar, and between the rear shock towers/rear seats, is certainly something that can be beneficial.

I also think that even if the main hoop feet push through the floorboards, you're still deflecting more energy than you would have without a bar. In that, I'll agree with swamp2 that it's better than nothing. I've seen a couple roll overs with bolt-in bars, and more didn't push through the floor compared to those that did.

A harness bar, in my opinion, is not a solution, and I wouldn't use one personally. Sure, it helps you with getting a set of harnesses to sit properly compared to the clip-in style Schroths that angle downward, but let's think about it for a minute. If you roll your car without a roll bar, the roof is at risk of coming down and smooshing your head. With a three point harness, if your head is getting pushed down, your body can 'lean' in towards the side of your body without the shoulder belt, maybe giving you enough room so that your neck won't break. With a 4, 5 or 6 point harness, your body has nowhere to go if the roof comes down. With a HANS or similar device, you have even *less* room for your neck and head to move. At least with a rollbar in place (welded or otherwise), the roof is less likely to contact your helmet. A harness bar does absolutely nothing for you in the event of a rollover.

Having had a rollbar in my last track car, which I still drove on the street, it's definitely a pain in the butt and introduces other issues besides just convenience. I definitely felt a lot better though when I was hoofing it at 135 into a braking zone, though.

[lucid]

Originally Posted by Ryan239

Attend more events and you'll see it happen; it's unfortunate but it's not uncommon.

I think having welded plates isn't a bad idea when using a bolt-in bar, as I have seen where in a rollover the main hoop did push through the floor of a vehicle, but I don't think not having them makes you any less safe than you would be without any sort of rollbar. I'd still take a bolted in (only) roll bar over no roll bar any day of the week.

A roll bar isn't only going to help you in a rollover situation, either. A side impact, depending on where you are hit, and a rear impact (also depending on where you are hit) are both incidents that can and do happen at the track. Having the additional protection at the 'B' pillar, and between the rear shock towers/rear seats, is certainly something that can be beneficial.

I also think that even if the main hoop feet push through the floorboards, you're still deflecting more energy than you would have without a bar. In that, I'll agree with swamp2 that it's better than nothing. I've seen a couple roll overs with bolt-in bars, and more didn't push through the floor compared to those that did.

A harness bar, in my opinion, is not a solution, and I wouldn't use one personally. Sure, it helps you with getting a set of harnesses to sit properly compared to the clip-in style Schroths that angle downward, but let's think about it for a minute. If you roll your car without a roll bar, the roof is at risk of coming down and smooshing your head. With a three point harness, if your head is getting pushed down, your body can 'lean' in towards the side of your body without the shoulder belt, maybe giving you enough room so that your neck won't break. With a 4, 5 or 6 point harness, your body has nowhere to go if the roof comes down. With a HANS or similar device, you have even *less* room for your neck and head to move. At least with a rollbar in place (welded or otherwise), the roof is less likely to contact your helmet. A harness bar does absolutely nothing for you in the event of a rollover.

Having had a rollbar in my last track car, which I still drove on the street, it's definitely a pain in the butt and introduces other issues besides just convenience. I definitely felt a lot better though when I was hoofing it at 135 into a braking zone, though.

The main issue is what might happen to you if the rollbar deforms significantly since you will be attached to/around it. You could be crushed or poked. The bar going through the chassis is not a problem per say in that regard as you car is probably the last thing you'd think about if you were to roll over. Yes, a bolt-in roll bar would protect you in a non-rollover crash as well, but the concerns I noted above would still apply, but probably to a lesser degree.

You have a good point about what a harness bar would do to you in a car that doesn't have roll-over protection if you end up rolling over. That has been discussed in some detail in another thread.

All I can say is that I don't want to be in a car without a full cage next year, which means a dedicated track car. Something with less power would be good as well to keep the top speeds down. Maybe some kind of spec series car...

[Ryan239]

Originally Posted by lucid

The main issue is what might happen to you if the rollbar deforms significantly since you will be attached to/around it. You could be crushed or poked. The bar going through the chassis is not a problem per say in that regard as you car is probably the last thing you'd think about if you were to roll over. Yes, a bolt-in roll bar would protect you in a non-rollover crash as well, but the concerns I noted above would still apply, but probably to a lesser degree.

You have a good point about what a harness bar would do to you in a car that doesn't have roll-over protection if you end up rolling over. That has been discussed in some detail in another thread.

All I can say is that I don't want to be in a car without a full cage next year, which means a dedicated track car. Something with less power would be good as well to keep the top speeds down. Maybe some kind of spec series car...

Yeah, a bolt in setup is a compromise all around, but if you look at most welded-in setups, they aren't using much more of a footplate in terms of size; I think where they'll really help is by angling the footer up along the side and helping to secure the structure in more spots than just the floorboards.

Going to a fully caged car is definitely a smart idea. It's a lot of extra baloney to deal with, cause now you need a truck and a trailer, someplace to store the truck and trailer, but from a safety perspective it's a lot better.