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My $.02 is you should never skimp on safety equipment and things that make you stop (I.e. Brakes and tires). While the bolt-in harness bar doesn't provide true rollover protection, it does provide a secure anchor so you can use 5 or 6 point harnesses. Coupled with a head/neck restraint, I feel this greatly increases the safety margin vs the stock 3-point belt system. I feel this is more than adequate for DE in a street car. I will also say that once you drive with a 6-point harness, you won't want to go back to a 3-point belt. It's much easier to relax and be smooth when you're not bracing yourself against the door and center console with your knees. I have LWB seats, Schroth 6-point GT3 harnesses, and a Cantrell harness bar. Id be happy to talk more specifics with you if you'd like
In the ROW cars (I'm in Australia) we get the Clubsport option for all GT cars purchased from Porsche. With than comes a rear bolt-in cage plus the option of buying the front section direct from Porsche motorsport (I did this for my GT4). The carpets and sound proofing comes prepared with pop-out cutouts to accommodate the bolted floor mounts. If you buy the front section you get a VIN specific FIA homologation certificate and the whole setup is approved for motorsport activities and is fully tested. It provides excellent rollover and side intrusion protection. So yes, a properly designed and installed bolt-in rear cage will provided excellent roll over protection as well as adding stiffness to the whole car if it is mounted off the rear strut tops. It you have seen a car barrel roll at a race track you will understand why you should have one. When things go wrong at 150mph it takes a long time to come to a rest!
I think your senses are right. Most all the aftermarket bolt in options are marketed as harness bars and don't claim any roll over protection even though they have roll hoops and appear to add roof support. It isn't so much a weld in vs. bolt in difference since I think you can have equally strong solutions either way but more an issue that there aren't reinforced hard points on the body for mounting like there is in the factory clubsport and the aftermarket solutions bolt up to existing mounts not necessarily intended or tested for those kinds of crash loads.
There's a lot of debate around the safety of 6pts without rollover protection but from all the research I've read, I do believe there's a net safety benefit to having 6pts with or without the roll protections. From the anecdotal "data" out there, most accidents don't involve the car rolling and even when there is a roll, a majority of injuries are from expulsion from the car or impact with things in the car (roof included) from occupants not being secure in their seats, all scenarios in which a 6pt would be beneficial. Yes, of course a roof collapse and 6pts could be devastating without roll protection and certainly it's a serious risk if unlikely.
All that said, after a year with just the 6pts attached to the BK mounts I'm getting a bolt-in roll bar installed. I'm assuming any additional rollover protection will be minimal but there's a lot of safety religion and assumptions out there and some groups get nervous when they see 6pts and no roll bar, irrespective of how effective that roll protection may actually be. Installing a bolt in roll bar is just easier as far as getting through tech, making passengers feel comfortable in the car, and not having to answer questions as to whether or not I understand the safety implications of running 6pts without roll protection... or at least the appearance of roll protection.
I think your senses are right. Most all the aftermarket bolt in options are marketed as harness bars and don't claim any roll over protection even though they have roll hoops and appear to add roof support. It isn't so much a weld in vs. bolt in difference since I think you can have equally strong solutions either way but more an issue that there aren't reinforced hard points on the body for mounting like there is in the factory clubsport and the aftermarket solutions bolt up to existing mounts not necessarily intended or tested for those kinds of crash loads.
There's a lot of debate around the safety of 6pts without rollover protection but from all the research I've read, I do believe there's a net safety benefit to having 6pts with or without the roll protections. From the anecdotal "data" out there, most accidents don't involve the car rolling and even when there is a roll, a majority of injuries are from expulsion from the car or impact with things in the car (roof included) from occupants not being secure in their seats, all scenarios in which a 6pt would be beneficial. Yes, of course a roof collapse and 6pts could be devastating without roll protection and certainly it's a serious risk if unlikely.
All that said, after a year with just the 6pts attached to the BK mounts I'm getting a bolt-in roll bar installed. I'm assuming any additional rollover protection will be minimal but there's a lot of safety religion and assumptions out there and some groups get nervous when they see 6pts and no roll bar, irrespective of how effective that roll protection may actually be. Installing a bolt in roll bar is just easier as far as getting through tech, making passengers feel comfortable in the car, and not having to answer questions as to whether or not I understand the safety implications of running 6pts without roll protection... or at least the appearance of roll protection.
thanks for the cogent reply.
especially that last phrase, "the appearance of roll protection"...
I'm coming from my purpose built E36 M3 track car. (which I drove for nearly 2 seasons) It was street legal, but a half stripped (everything behind the driver's seat) interior to accomodate a weld-in roll hoop and harness bar built by Piper Motorsports.
Not the finished product, but an "in-progress" pic, shortly after picking her up.
The 4-pointer, with diagonal cross-bracing of the main hoop and rear struts. The feet of the main hoop was welded to the floor with reinforcement. (not pictured)
An "extreme" option (and likely permanent) is to give Piper a call and see if they can fabricate at least a welded in main hoop. ( I understand that I may lose full range of aft adjustment of the LWBs. ) And install in a way where stock carpeting and trim can be reinstalled to look like bolt-in roll bar.
Just an opinion from a mechanical engineer, but if you have the harness/roll bar that extends down and is secured by the seat belt bolt, I would say in many cases that configuration would provide a non-trivial amount of roll-over protection.
The whole idea is about energy absorption, which in this case is done by metal (the roll bar) deforming. The benefit of a welded-in roll bar is that as the bar is loaded from the top, the bar will deform and spread the load (via the pipe) to a number of attachment points. The more parts that deform (that are not parts of your body) the better - this means the kinetic energy you and the car have is being dissipated.
Bolts are strong, but the forces involved in high-speed crashes go beyond our intuition (for the large majority of people) because we do not experience these things routinely. In these types of extreme events, bolts can and will fail. I've been involved in crash tests (not cars) where grade 8 bolts pop off like buttons on a shirt.
If bolts fail, but the roll bar stays essentially in place, then you are likely in just as good of shape as with the welded cage. If the base of the bars "slip" after breaking the bolts, there is still some energy dissipation, but maybe not as much as if the bases stayed attached.
Another thought experiment...imagine the cross sectional area of bolts that might attach a bar: N*Area = N*pi*r^2 (N=number of bolts), then imagine the area of a weld bead that would be something like L*w, where L is length and w is width of the weld. The bolt area will generally be far less...thus, makes sense that method of attachment is weaker.
Bolts popping like shirt buttons is not comforting. In addition to cost, weight, and questionable actual rollover protection, adding a steel bar right behind your head with no helmet is an added liability, doubly so if there's any doubt that it won't stay in place in an accident.
That said, I'm still getting a bolt in "roll" bar installed tomorrow. It will bolt up to the firewall near the OEM seat belt receptacles and rear shock towers like most of the aftermarket options. Hopefully it will add a little roof support and with the LWBS be out of range of my unhelmeted head while driving on the street.
There is one company (forget who) that offers a bar that runs all the way down to bolt to lap belt bolts..... don't buy that one.
09-22-2017, 11:43 AM
True roll over protection of bolt-in "roll bars"
