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It would also be great to know what grade bolts the rollbar manufacturers supply with the bars, and if there are any options for reinforcement plates (or an explanation why we won't need them). I plan on ordering a rollbar soon so it has lots of time to get to my dealer.
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We may be a bit biased, but we believe the CMS Performance roll bar from Competition Motorsport is the best option for the 991 GT3 and GT3RS (both the previous and the "dot-two" versions). It is fully TIG welded from domestic 1.75-inch, 0.120" wall 4130 CrMo tubing, which is superior in terms of rollover protection to typical DOM steel due to its far higher strength and resistance to deformation. This is heavier-gauge CrMo than most use, allowing us to use a more open design to give you a clear rear view while maintaining ultimate harness strength and rollover safety.
Where our design differs from most is in the placement of the harness bars, which reside in the main hoop, not the rear kickers. This puts the harness shoulder strap location not only at the correct height relative to the driver's shoulders, it also puts the shoulder straps at the correct distance from the driver (8" or less). Mounting the shoulder straps further back is not considered by seat and harness manufacturers as being as safe, and in any case requires use of special harness straps made to elongate less in an impact.
The CMS bar is precision manufactured to install seamlessly into any 991 or 991.2 GT3/GT3RS with only minor carpet trimming at the B-pillar bulkhead. We provide Grade-8 hardware, and it is powder coated in any of our precisely color-matched powder colors -- always for free, as is shipping. Also, we customarily offer Rennlist members 10% off on roll bars; just enter Coupon Code CMSRLIST at checkout.
Give us a call or PM us if you have questions or want to talk about roll bar design, installation, etc.
CMS 991 GT3 Roll Bar Front View
CMS 991 GT3 Roll Bar Rear View
Installed in customer car; note optimal placement of the harness bar.
Harness mounting bar at the proper height and distance relative to the driver's shoulders.
Fully TIG welded and custom powder-coated in the Porsche-matched color of your choice.
View through the rear window; you have a clear rear view with the CMS Roll Bar.
Also, all CMS roll bars are built by us from start to finish so we can control every aspect of quality, workmanship, precision fitment, and finish. They are powder coated by our on-site sister company, Competition Coatings, so the time from your order to shipment is typically only two or three days regardless of what custom color you choose.
New member with a 2018 allocation with 6 speed MT and LWB’s. Planning to put in a roll bar and 6 point harnesses. Has anyone used either the BBi or GMG mounting brackets for the anti-submarine straps? Both look nice. I am narrowing down my bar selection to the BBi, GMG or the CMS bars. I like the horizontal bar closer to the seats even though the CUP car bar that most are based are mounted on the back portion exceeding the recommended 8inch distance to the seat backs. I like the idea of the eye bolts to do a clip on mounting to remove the harness when not on the track. Eliminated Cantrell since you have the cut the $1400 plastic interior covers. I found the weight on the GMG at 41 lbs and CMS at 54 lbs. Can’t find the BBi weight. I do like the idea of the CMS bars using Docol R8 steel. Supposedly less issues with fatigue (I have never heard to a bar failure in a DE car using CroMo steel but it looks better on paper). Don’t know much about the Alex bar which is also Docol R8. Any members with experiences on these bars would be appreciated.
I'm running the GMG LMS bar, with Schroth Porsche-specific carbon bucket 4pt belts and am THRILLED with the setup. No lap belt in the way, easy install without any additional modifications and virtually all the safety of 6pt, via the ASM technology long proven by Schroth.
For the occasional track car, this is the best setup IMO.
I'm running the GMG LMS bar, with Schroth Porsche-specific carbon bucket 4pt belts and am THRILLED with the setup. No lap belt in the way, easy install without any additional modifications and virtually all the safety of 6pt, via the ASM technology long proven by Schroth.
For the occasional track car, this is the best setup IMO.
thanks! Do you have photos of how those belts work and the shroth model?
We do not have a photo of the 4 point setup with our bar, but here is what the belt looks like but its would be identical to this configuration minus the crotch belt.
Originally Posted by saildoc
thanks! Do you have photos of how those belts work and the shroth model?
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Nice setup there! The ASM belts are a great option for a "Double-duty" car
Originally Posted by Mvez
I'm running the GMG LMS bar, with Schroth Porsche-specific carbon bucket 4pt belts and am THRILLED with the setup. No lap belt in the way, easy install without any additional modifications and virtually all the safety of 6pt, via the ASM technology long proven by Schroth.
For the occasional track car, this is the best setup IMO.
Fall-Line Motorsports will have one ready soon as well!
For those that don't know, Fall-Line is very highly regarded for building some of the best production based car Roll Cages.
They're in Buffalo Grove IL
New member with a 2018 allocation with 6 speed MT and LWB’s. Planning to put in a roll bar and 6 point harnesses. Has anyone used either the BBi or GMG mounting brackets for the anti-submarine straps? Both look nice. I am narrowing down my bar selection to the BBi, GMG or the CMS bars. I like the horizontal bar closer to the seats even though the CUP car bar that most are based are mounted on the back portion exceeding the recommended 8inch distance to the seat backs. I like the idea of the eye bolts to do a clip on mounting to remove the harness when not on the track. Eliminated Cantrell since you have the cut the $1400 plastic interior covers. I found the weight on the GMG at 41 lbs and CMS at 54 lbs. Can’t find the BBi weight. I do like the idea of the CMS bars using Docol R8 steel. Supposedly less issues with fatigue (I have never heard to a bar failure in a DE car using CroMo steel but it looks better on paper). Don’t know much about the Alex bar which is also Docol R8. Any members with experiences on these bars would be appreciated.
Saildoc,
Thank you for considering our bar! Our bar weighs 50 pounds and we do offer an option for add threads for eyelet bolts. Our bar weights 50 pounds and here are pictures of our sub belt brackets to give you a better idea of how they are installed.
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I have been thinking about and researching the whole harness bar issue in preparation for the arrival of my 2018 991.2 with LWB’s. Warning, this is long winded and I am not an engineer-just an active student of life.
I come from a DE background where I had a spec boxster and E36 M3 both with full welded cages so I have some familiarity with driver safety.
My track interest will be limited to nicer tracks like MSR and COTA. This car is too awesome to not experience its full potential and I feel it would be a waste. I hope I never had an off track event and the possibility of needing protection of full bucket seats and 6 point harness are slim. As other posters have pointed out the real function of these harness bars (they are not roll bars) is a solid mounting point for a 6 point harness with a HANS device. This is the key I think-this is a very fast car and deceleration injuries are what will hurt your neck or back if you are not properly restrained. Having slid off the track before with a race bucket/HANS/6 point harness in my track cars and not hitting anything, the G-forces on your head and neck while you whip around is scary and I am glad that never happened with just a 3 point belt street setup.
A harness bar gives a solid mount for a 6 point set up. These bars are only attached at four point with bolts-if you compare to a race cage that is welded in at multiple points to reinforced plates throughout the structure of the car-there is no comparison in strength and resistance to crumpling. So my main goal with a harness bar is to be sure it keeps its integrity during a roll over or even worse an end over. When you look at videos and photos of street cars that have been through these events the roofs do deform a lot but what is interesting is that the impacts are at angle rather than straight down on the roof-sort of an offset torsional force. What is the significance of this fact is that most of these bars appear to be strongest in compression loading-as if the car is lifted by a crane and dropped on its roof. This is not a realistic real world situation. How is this significant? Most bars available have some kind of a joint system-while they look strong I wonder how well they will hold up under severe offset or oblique loading and I worry they may fail. Failure obviously means you may loose your harness effectiveness or worse get a fracture bar end through your helmet...
There is an issue of the steel that is available: most use chromoly steel-strong and light but potentially brittle-especially at the weld zones and post weld stress relief is needed-that is why there are not used in race cages-you can’t really heat treat the whole car. The alternative material DOM is supposedly more resilient and less prone to stress failure.
So if we eliminate the Cromoly steel cages we are left with Cantrell, CMS and Alexshop. I may have missed others but this is what I found.
Of these three I eliminated the Cantrell and the CMS
Bar because they are multipiece .That leaves the Alex bar which is one piece welded from DOM and has the horizontal attachment closer to the seats keeping the belt length as short as possible.
Ok, thanks for reading to the end-anyone feel free to dispute or chin in. Also if you have an Alex bar let me know how you like it and post a pic of the view through the rear view mirror-thanks!
I have been thinking about and researching the whole harness bar issue in preparation for the arrival of my 2018 991.2 with LWB’s. Warning, this is long winded and I am not an engineer-just an active student of life.
I come from a DE background where I had a spec boxster and E36 M3 both with full welded cages so I have some familiarity with driver safety.
My track interest will be limited to nicer tracks like MSR and COTA. This car is too awesome to not experience its full potential and I feel it would be a waste. I hope I never had an off track event and the possibility of needing protection of full bucket seats and 6 point harness are slim. As other posters have pointed out the real function of these harness bars (they are not roll bars) is a solid mounting point for a 6 point harness with a HANS device. This is the key I think-this is a very fast car and deceleration injuries are what will hurt your neck or back if you are not properly restrained. Having slid off the track before with a race bucket/HANS/6 point harness in my track cars and not hitting anything, the G-forces on your head and neck while you whip around is scary and I am glad that never happened with just a 3 point belt street setup.
A harness bar gives a solid mount for a 6 point set up. These bars are only attached at four point with bolts-if you compare to a race cage that is welded in at multiple points to reinforced plates throughout the structure of the car-there is no comparison in strength and resistance to crumpling. So my main goal with a harness bar is to be sure it keeps its integrity during a roll over or even worse an end over. When you look at videos and photos of street cars that have been through these events the roofs do deform a lot but what is interesting is that the impacts are at angle rather than straight down on the roof-sort of an offset torsional force. What is the significance of this fact is that most of these bars appear to be strongest in compression loading-as if the car is lifted by a crane and dropped on its roof. This is not a realistic real world situation. How is this significant? Most bars available have some kind of a joint system-while they look strong I wonder how well they will hold up under severe offset or oblique loading and I worry they may fail. Failure obviously means you may loose your harness effectiveness or worse get a fracture bar end through your helmet...
There is an issue of the steel that is available: most use chromoly steel-strong and light but potentially brittle-especially at the weld zones and post weld stress relief is needed-that is why there are not used in race cages-you can’t really heat treat the whole car. The alternative material DOM is supposedly more resilient and less prone to stress failure.
So if we eliminate the Cromoly steel cages we are left with Cantrell, CMS and Alexshop. I may have missed others but this is what I found.
Of these three I eliminated the Cantrell and the CMS
Bar because they are multipiece .That leaves the Alex bar which is one piece welded from DOM and has the horizontal attachment closer to the seats keeping the belt length as short as possible.
Ok, thanks for reading to the end-anyone feel free to dispute or chin in. Also if you have an Alex bar let me know how you like it and post a pic of the view through the rear view mirror-thanks!
I’ve gone through your same logic sequence myself and come to the conclusion that I think I just want harness mounting, not a pseudo roll bar. Since nobody offers such a thing for the 991, I plan to get one custom fabricated that attaches to the same rear shelf mounting points as most of the pseudo roll bars.
My goal (which appears achievable) is minor slot cutting to the opener rear generic 991 carpet over the engine area for belt pass through, and zero mods to the seat shelf carpet with the GT3 stitching.
If I break down and get a pseudo roll bar out of laziness, I like the custom layout BBi bars the best (love the curved main hoop, that is slick).
01-12-2018, 10:26 PM
