Roll cage for TT - options?
Looking to set up an NB for HPDE/TT, want a cage for safety, but don’t need full safety of a W2W cage. Hard to pass up spec Miata cages since they are refined and effective. Was thinking of either Advanced Autosports or Miatacage without door bars. Questions: - Can I keep heat and a/c with either or other cage? AA says no a/c, not sure about MC - Most spec Miata cages don’t seem to have room for a passenger seat, was thinking this would be good for instructors - I want the car to look nice inside, not a pure track car, so want a bar that fits tight to the edges of the car Any thoughts? |
How fast is your car? In the S1/ST4 cars, we are quickly trending towards the realization that Spec Miata cages are grossly under-built for the speeds we're seeing.
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A cage should be a one time thing, don't think of it as something that you'll later upgrade.
Do it once, do it right. |
I am using the Miatacage and still have A/C and heat but it requires some adjusting behind the dash. They include instructions for this. I used only the lower door bar so I didn't have to cut the doors. I did raise the lower door bar to a higher position since not using the upper.
It was getting to be too fast for no cage at all but this is a compromise. Be as safe as you want to be. It's not as safe as staying home. |
Thanks sixshooter, I actually was using your set up as an inspiration. I’m only looking at TT5 at most right now, so staying N/A. May have a k swap in the future though. Anything you you regret or would do differently? Can you get a passenger seat in there? If you’ve got working a/c and heat that’s what I want. |
As Andrew observed, if you are not otherwise limited by rules, go big. Traditional Spec Miata cages are floor mounted only. They provided only the minimal roll over and intrusion protection. Beyond that, they offer only the minimal amount of torsional stiffness increase compared to a fully integrated cage. NASA ST rules allow almost a full FIA cage in ST5. In Supermiata, we are adopting more open rules for cages even in S2 (140whp). S1 goes a step further by allowing a full integrated FIA cage with extensions to the front shock mounts. The merits of a 12+ pt cage attached to the firewall and door jambs go far beyond mere intrusion protection but that should be enough. In most cases, the cost and weight only increase slightly and the car is future proof for additional power/grip/ aero loads.
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Good point Emilio, I didn’t think about the additional rigidity. I do agree on only doing it once. Another thing leading me in the direction of a SM cage though is resale value should I want to go in a different direction down the road. I could add the NASCAR door bars and sell pretty easily. Question on the additional cost. My perception was that a FIA spec cage was more along the lines of a custom cage, which I was thinking would be in the $4-5k range, where as a Miatacage + install could be half that. Do you think that is right? |
A good cage Builder will charge you enough labor on top of the cost of a generic Miatacage to cover the cost of a custom cage generally. So that the perception that you can just buy the $900 Miatacage kit and be done overlooks that it will cost more than that to actually put it in by a competent fabricator. It only takes one flawed weld to compromise the entire cage.
In Supermiata here in California we often tech cages of cars that were approved by scca and NASA for spec Miata. Not a single one of them was properly installed. Not one. We have failed several due to incomplete welds or the structure simply being incorrect. This exposure to the general low quality standard of most cages in Miatas concerns me. The true challenge is finding a competent fabricator, not designing the cage. Shop around but I often hear prices between 1700 and 2500 for a custom cage. |
I agree with the statement that a good fabricator is hard to find and worth the money when you find him. My shop had an expert welder come in after it was tacked together to finish it.
Mine has a passenger seat. |
I like the advanced autosport cage a lot and have seen them tested. Not sure I’d want that in my street driven TT car though. Where are you located? CA has a couple good options, the Midwest has a great builder in STL. |
I’m in Cincinnati, willing to drive to find a good cage builder. From an earlier thread: Mark McMahan is the guy to go to for a cage in the Mid-West. He is in Akron. |
Originally Posted by Maxhouse97
(Post 1506487)
I’m in Cincinnati, willing to drive to find a good cage builder. From an earlier thread: Mark McMahan is the guy to go to for a cage in the Mid-West. He is in Akron. |
Let an expert build it from scratch his way if he's really good. Discuss your wants and needs and see if you're comfortable with him. Look at some of his completed work for quality. Be sure he's right for you.
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You really have to decide if you want a street car? IE Blackbird Fabworx and airbag. Swapping seats for HPDE & TT. HANS if using 6 point harness.
Race car / track car full cage, spec Miata as a minimum FIA nice but then cant use for spec? They really should revise the spec cage to a more modern cage setup as Emilio suggests. IMHO I really cant see using a full cage on the street without a helmet and HANS? |
Originally Posted by Blkbrd69
(Post 1506660)
You really have to decide if you want a street car? IE Blackbird Fabworx and airbag. Swapping seats for HPDE & TT. HANS if using 6 point harness.
Race car / track car full cage, spec Miata as a minimum FIA nice but then cant use for spec? They really should revise the spec cage to a more modern cage setup as Emilio suggests. IMHO I really cant see using a full cage on the street without a helmet and HANS? |
Forgive me for skimming the OP too much. Agreed that a full cage for a street car is a very bad idea. Our general protocol for HPDE safety is to go either full OEM or full race & trailer. Don't mix. To that end, I switched my HNRS to a Simpson Hybrid-S that works with 6 pts in the race car or the 3 pt OEM in the GT350.
Full OEM means all the airbags, stock seat so airbag sensors are still active. Full race car means 6 pts, 6pt bar or full cage. Padded tubes, race wheel w/o airbag. FIA seat with halo. Nets on both sides. Fire system and hand held. And a trailer to tow it because those bars and lack of airbags are just asking for trouble on the street if you get hit. |
Originally Posted by emilio700
(Post 1506727)
General protocol for HPDE safety is to go either full OEM or full race & trailer.
Full race car means 6 pts, 6pt bar or full cage. Padded tubes, race wheel w/o airbag. FIA seat with halo. Nets on both sides. Fire system and hand held. And a trailer to tow it because those bars and lack of airbags are just asking for trouble on the street if you get hit. How far you go beyond that is really up to your personal risk tolerance for the pace you currently drive. I don't think full halo seats, nets, and complete fire suppression system is really necessary if you're not wheel to wheel. Are these things a good idea? Yes. But they are not imperative. |
Originally Posted by jpreston
(Post 1506490)
Take the car to Mark. I did a miatacage in my first miata and was never happy with it. After seeing a few of Mark's cages, I sold the car with the miatacage, bought a new NB, and took it to Mark. So much happier now. He does really great work.
He has amazing attention to detail, ability to adapt, and to customize anything to what you want with over 20 years of experience. |
Originally Posted by emilio700
(Post 1506727)
...Nets on both sides...
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Originally Posted by FatKao
(Post 1507180)
I'm getting very close to doing this as well. Seems most impact deaths these days are from occupant side pancaking against concrete.
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We running two nets on our Champ/Chump Car. We also have roof nets under our bolted on roof panel. Better safe than sorry. They don't weight much and we don't have to run arm restraints.
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I have been looking at rules for FIA roll cages. It appears that they spec 1.75" x .095 tubing for the main components of the cage and allow for 1.50" x .095 for the support bars such as a the backstays, diagonals and doorbars.
Am I reading that correctly? I haven't found any that specify tubing size by the weight of the car like some organizations do. |
Originally Posted by fmcokc
(Post 1508858)
I have been looking at rules for FIA roll cages. It appears that they spec 1.75" x .095 tubing for the main components of the cage and allow for 1.50" x .095 for the support bars such as a the backstays, diagonals and doorbars.
Am I reading that correctly? I haven't found any that specify tubing size by the weight of the car like some organizations do. Up to 1500 lbs 1.375” x 0.095” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical), DOM, or Docol R8 (only) 1.500” x 0.080” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical), DOM, or Docol R8 (only) RACING AND COMPETITION 47 1501 - 2500 lbs 1.500” x 0.095” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical), DOM, or Docol R8 (only) 1.500” x 0.120” ERW* (No issuance of log books for cars with ERW cages) *Note- Specifications listed only for reference for inspection of grandfathered vehicles. 2501 - 3000 lbs 1.500” x 0.120” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical), DOM, or Docol R8 (only) 1.750” x 0.095” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical), DOM, or Docol R8 (only) 1.750” x 0.120” ERW* (No issuance of log books for cars with ERW cages) *Note- Specifications listed only for reference for inspection of grandfathered vehicles. 3001 - 4000 lbs 1.750” x .120” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical), DOM, or Docol R8 (only) No ERW allowed. Over 4000 lbs 2.000” x 0.120” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical), DOM, or Docol R8 (only) No ERW allowed. I'm sure SCCA and other commonly-referenced rulebooks are similar. The references above to "FIA" spec are mainly the use of IMSA style pyramid or 3D X doorbars and the A pillar reinforcement tubes. |
Make sure that your local tech will accept the cage prior to building true FIA spec cage.
There are a few major changes in the line of thought between FIA and all US organizations. |
Originally Posted by Blackbird
(Post 1508870)
Make sure that your local tech will accept the cage prior to building true FIA spec cage.
There are a few major changes in the line of thought between FIA and all US organizations. yes, some of their configurations are a bit different. |
Originally Posted by doward
(Post 1508866)
I'm sure SCCA and other commonly-referenced rulebooks are similar.
The references above to "FIA" spec are mainly the use of IMSA style pyramid or 3D X doorbars and the A pillar reinforcement tubes. Yes, all the org’s I have seen specify the size of the tubing based on the weight of the car. I find it odd that the FIA only gives 1 spec for tubing size that I can find. What at is the general thought/ consensus on the additional A pillar reinforcement bars and the pyramid x shaped door bars? Are they considered as strong or stronger than the NASCAR style bars? |
Originally Posted by fmcokc
(Post 1508886)
Yes, all the org’s I have seen specify the size of the tubing based on the weight of the car. I find it odd that the FIA only gives 1 spec for tubing size that I can find. What at is the general thought/ consensus on the additional A pillar reinforcement bars and the pyramid x shaped door bars? Are they considered as strong or stronger than the NASCAR style bars? |
Originally Posted by Blackbird
(Post 1508870)
Make sure that your local tech will accept the cage prior to building true FIA spec cage.
There are a few major changes in the line of thought between FIA and all US organizations. |
Originally Posted by fmcokc
(Post 1508886)
What at is the general thought/ consensus on the additional A pillar reinforcement bars and the pyramid x shaped door bars? Are they considered as strong or stronger than the NASCAR style bars? Keep in mind that FIA bars take a massive amount of room from the door opening and that might not work for many drivers for quick exit purposes. To avoid that issue in Morpheus, I replaced the tubes with a 3D curved gusset which is a great way to spend 20+ hours fabricating one piece of sheet metal, even if you're well versed at this - https://cimg7.ibsrv.net/gimg/www.mia...adedd1694b.jpg |
Originally Posted by emilio700
(Post 1506369)
As Andrew observed, if you are not otherwise limited by rules, go big. Traditional Spec Miata cages are floor mounted only. They provided only the minimal roll over and intrusion protection. Beyond that, they offer only the minimal amount of torsional stiffness increase compared to a fully integrated cage. NASA ST rules allow almost a full FIA cage in ST5. In Supermiata, we are adopting more open rules for cages even in S2 (140whp). S1 goes a step further by allowing a full integrated FIA cage with extensions to the front shock mounts. The merits of a 12+ pt cage attached to the firewall and door jambs go far beyond mere intrusion protection but that should be enough. In most cases, the cost and weight only increase slightly and the car is future proof for additional power/grip/ aero loads.
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Originally Posted by fmcokc
(Post 1508946)
Do you have any details/pics of the extensions to the front shock mounts? Would like to see what you or others are doing in this area. Additionally is important to remember that the Miata is not a strut car so the actual shock tower doesn't have that much load going through it. The highest forces are going into the subframe mounts which are those two big studs that poke out the bottom of the frame rail. Those forces are trying to twist the front of the car and deflect the frame rails out of the same plane. So that's really what you are trying to reinforce, box or triangulate. Triangulation preferred as it uses a lot less material than a box, for a given stiffness. From a safety standpoint it is intrusion. Like most small cars keeping the front wheel and suspension out of the driver's footwell in a major frontal impact is a challenge. A simple triangulated brace anchored at the door bar foot and a little higher up and extending forward to the stiffest part of the firewall helps hugely in this regard. |
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