Automotive Plus Twin vs Single Hoop Roll Bar for NA/NB

twr7cx · Postby **twr7cx** » Tue Jan 23, 2018 9:15 am

I'm currently beginning my search for a roll bar for my NA6. Have been looking at the Automotive Plus offerings and noticed that the Single Hoop seems to sit significantly higher above the seats than the Twin Hoop in their ads pictures (using the top height of the seats to judge the roll bars height from):

Is this an accurate assumption or is it because of different seat positions (e.g. recline) or NA compared to NB configuration?

Personally, I like the look of the Twin Hoop model but seems a silly choice for a roll bar if providing less head protection...

KevGoat · Postby **KevGoat** » Tue Jan 23, 2018 9:30 am

The images are a bit deceptive as the twin hoop is using NB higher back seats. Twin hoop bar gives improved rear vision but cross bar in the other one may give more protection. There is a taller bar available too but that one restricts rear seat movement.

Just to add...sitting in the stock seats, none if them will be above your head or not much anyway. The roof line restricts how tall they can be without fouling.

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ManiacLachy · Postby **ManiacLachy** » Tue Jan 23, 2018 9:46 am

You're comparing photos with NA seats to photos with NB seats, the seat height is different not the roll bar height. Both roll bars will be as tall as possible while fitting under the roof.

I have the twin hoop, with stock seats my head was probably just higher than it. With my Lotus Elise seats I'm comfortably under it. Even with the stock seats having a roll bar is better than not having one, IMO.

The twin hoop will make it easier to raise the roof while seated. I reach back between the seats and pull the roof up, and can get it to the header in one motion. With a cross bar there as it is with the single hoop this would be a bit harder, I'd have to hand over the roof to the other hand to complete the motion. Small thing, but if you raise/lower the roof often it might be worth considering.

KevGoat · Postby **KevGoat** » Tue Jan 23, 2018 9:58 am

I don't have the arm strength to reach back and pull the roof up ... I use this ...

Sorry for lousy photos just took them quickly

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ManiacLachy · Postby **ManiacLachy** » Tue Jan 23, 2018 10:15 am

Doesn't that then dangle in front of you as you drive with the roof up? I still have the mobility to reach and pull it up without a strap. But either way, a cross bar would interfere to a degree.

KevGoat · Postby **KevGoat** » Tue Jan 23, 2018 10:35 am

Tucks into the roof cross bar out of the way. Would still work with the other roll bar cross bar same as using it with my windbreak. Copied the idea years ago from another forum member.

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Code4 · Postby **Code4** » Tue Jan 23, 2018 11:57 am

I have the twin hoop on my NB8A and it sits 110mm higher than the stock seats. I chose it purely for the retro look, to fit my speed deck onto and the decrease in rear body NVH it offers.

The single bar imo would give slightly better protection. The taller race version means even more protection. I'm reasonably sure you cant use a roof, either hard or soft, with the tall version.

No matter what, I simply hope to never be in an MX5 if it rolls.

Snowmotion · Postby **Snowmotion** » Tue Jan 23, 2018 11:59 am

ManiacLachy wrote:Doesn't that then dangle in front of you as you drive with the roof up? I still have the mobility to reach and pull it up without a strap. But either way, a cross bar would interfere to a degree.

I used a Lanyard that you are given at many events where the end of the Lanyard can be clipped off. This way, if I drive with the roof up I can unclip the strap and I put it around the gear leaver.

KevGoat · Postby **KevGoat** » Tue Jan 23, 2018 12:34 pm

Don't even know it's there - even the bit hanging down isn't in the mirror at all. Never fallen down or blown around with windows down.

1600Dave · Postby **1600Dave** » Tue Jan 23, 2018 8:09 pm

What purpose do you want it for ? ie if used for motorsport, do you need to consider CAMS requirements ?

twr7cx · Postby **twr7cx** » Wed Jan 24, 2018 12:26 pm

1600Dave wrote:What purpose do you want it for ? ie if used for motorsport, do you need to consider CAMS requirements ?

Street car that I purchased to take to the occasion social track day/skid pan session. Maybe would like to also try Khanacros and/or motorkahana in the future too.

twr7cx · Postby **twr7cx** » Wed Jan 24, 2018 12:31 pm

I received the following reply from automotive plus parts when I put the questions to them:

Hi ,
Thanks for your enquiry. We sell 4 x different styles of roll bars. 2 of the styles are what we call a Tall Boy Roll Bar. This bar is 50mm taller than the std height bars but it does come forward 70mm to accommodate the arc of the roof etc. essentially you lose 70mm of seat travel with these bars. The std height bars like the one pictured for $825, you do not lose any seat travel. it is all about the height and arc of the roof as to what we can fit in.
They are all relatively close to the roof but in different positions. The Twin Hoop bar is still an effective roll over structure,
Dave

They don't actually confirm that the Single and Twin Hoop bars are the same height, but they do confirm that the Tall Boy Roll Bars would loose seat travel which makes them definitely not an option. I clarified my question on the standard height bars and received:

They essentially should be the same height. The Single bar looks taller as it follows the whole roof line and is straighter where the twin hoop bends etc.
Dave

1600Dave · Postby **1600Dave** » Wed Jan 24, 2018 7:09 pm

twr7cx wrote:
1600Dave wrote:What purpose do you want it for ? ie if used for motorsport, do you need to consider CAMS requirements ?

Street car that I purchased to take to the occasion social track day/skid pan session. Maybe would like to also try Khanacros and/or motorkahana in the future too.

No worries, only asked as neither of the ones pictured would be CAMS compliant. Should be fine for your use though.

StillIC · Postby **StillIC** » Wed Jan 24, 2018 7:16 pm

1600Dave wrote:No worries, only asked as neither of the ones pictured would be CAMS compliant...

Why not?

twr7cx · Postby **twr7cx** » Wed Jan 24, 2018 9:30 pm

1600Dave wrote:No worries, only asked as neither of the ones pictured would be CAMS compliant. Should be fine for your use though.

Thanks for pointing that out. Are you able to please explain how to are able to identify that it is not CAMS compliant? While the ad does not say that it is CAMS compliant, it does indicate that it’s built towards their spec requirements:

Strength of Roll Bar Structure
* The TB roll bar harness mounts meet the strength requirements of ADR 5.
* The TB roll bars use CAMS specification tubing – 44.5 mm Seamless tube, 2.5mm wall thickness.
* The TB roll bar mounts exceed the State/NCOP Regulation of 6mm thick mounting plates and a minimum of two M10 8.8 grade high tensile bolts at each mount.

Design and Dimensions
...
* The TB roll bar harness mounts comply with ADR 5 geometry (ie. low rearward strap angle to limit compression of the spine).