Why did we rip out our roll cage and build a new one?

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Update by Tom Suddard to the Mazda Miata project car
Jan 15, 2024 | Mazda, Mazda Miata, roll cage

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A year ago, as we were writing about building better door bars in our LFX-swapped Miata, we included this sentence:  “(And before you email us, yes: Our Miata’s front down bar is in a less than ideal position. We’ll address that in a future update.)”

[Can upgrading safety also improve comfort? | Project Endurance Race Miata]

We didn’t have the space to fully elaborate at the time, but here’s what we were alluding to: When we purchased our Miata, it came with a cage already installed.

Awesome, right?

Well, mostly. Though the cage passed tech and was built fairly well, we were never completely happy with how it fit the car. In theory, a cage should be as large as possible, fitting into the chassis like a ship in a bottle, and keeping its dangerous tubes as far away from the driver as possible. 

In practice, well, our Miata fell short of those ideals. Every tube in the cage seemed to be a few inches closer to us than it needed to be, a fact we remembered every time we struggled to fit a seat into the car or whacked our head into a bar on track.

And unlike the door bars we re-made, the rest of the cage couldn’t really be fixed. Instead, our only option was to cut it out and start fresh. 

To be fair, Miatas are tough to cage–there just isn’t much room to work with, and experienced Miata cage builders seem to have more tricks up their sleeves than the average welder.

That’s why we ordered $500 worth of steel and planned a visit to Nine Lives Racing to finally build a proper cage in our Miata.

And before you ask: No, Nine Lives won’t build a cage in your car. But owner Johnny Cichowski is a friend and an experienced cage builder, and was happy to do us a solid in trade for some driving time at our next event. We’d build the cage out of 1.5” x 0.120 wall DOM tubing, with the goal of building a big, safe cage with plenty of room for any driver.

What’s the first step? It’s Sawzall time! We started by removing the seat from the car, then cut out the old cage and ground its spreader plates flat. That gave us a blank canvas to work with. 

Next, it was time to cut–and by “cut” we don’t mean trim a little sheet metal. We mean cut giant hunks out of the car.

Our Miata’s main hoop originally landed on the floor behind the driver’s seat, which is bad for a few reasons: First, it required that the main hoop be bent in two planes, a major no-no in most rulebooks.

And second, even with the dangerous bend, it still interfered with our driver’s seat.

To make more room, we’d re-locate the main hoop to the Miata’s rear bulkhead. And to get to it, we sliced about five pounds of metal off the car. Goodbye, factory seatbelt and hard top mounts. Hello, room to work. 

With the cutting complete, we moved onto bending. Rather than the trial-and-error method we usually employ at home, Johnny uses a computer program called Bend-Tech to do the math.

By drawing each bar on the computer before building anything in the physical world, we were able to save tons of time and with little wasted material.

Main hoop installed, we moved onto the A-pillar bars. And again, we used a trick to get more space. Before, our cage’s front feet landed on the floor, blocking the dead pedal and providing a nasty point of leverage to break an ankle in a crash.

We moved these feet to the rocker panel, which is both a stronger mounting location and far away from our delicate bones.

We also wasted plenty of tube—including this first attempt at a driver's side A-pillar bar that ended up too close to our head:

After a few days of bending, cutting and notching, plenty of welding and more than a few tubes on the scrap pile, we were able to build a well-designed cage with way more space than before. Johnny even finished it off with a flashy custom dash and switch panel mount to replace our heavy steel solution from the last cage.

Here's a photo that shows the seat reinstalled in the same position as before—the old cage was literally rubbing a hole in the seat, while the new cage will let us slide it about four inches further back:

Cage complete, we’ll need to clean and paint everything, as well as weld in a few gussets. That will happen after our next event, because we’re not towing the Miata home from here: We’re towing it to the Tire Rack Ultimate Track Car Challenge! We’ll cover that in our next update.

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Comments
Msterbee
Msterbee Reader
11/21/23 1:57 p.m.

Am I the only person with a cage-building fetish?  

Rgvkiwi
Rgvkiwi GRM+ Memberand New Reader
11/21/23 2:07 p.m.

I know you said removing the down tube from the A-pillar ankle saves a broken ankle but it sure looks weird not going up to and tying in around the A-pillar footing....I don't think that would pass here in New Zealand being a few inches back.

lotusseven7 (Forum Supporter)
lotusseven7 (Forum Supporter) Dork
11/22/23 7:05 a.m.

Instead of putting the A-pillar downtube onto a "plinth box", I cut the tube into a plate formed along the inner sill. All of the Spec Miata cages that I've done are like this and I find it a cleaner installation with more leg room and no chance of ankle/heel/foot injury in the event of a collision. Just my way of doing it.

 

 

 

 

 

Rgvkiwi
Rgvkiwi GRM+ Memberand New Reader
11/22/23 2:07 p.m.

Thats a lot like mine  too. New Zealand.

ThumperUSMC
ThumperUSMC GRM+ Memberand New Reader
11/25/23 11:52 a.m.

Question, really... Do you know or can you recommend someone in the Pacific Northwest area that can, and is willing to do a Corvette Convertible roll cage that will not "destroy" the lines of the car and will still allow being able to put the top up for those rainy days the Northwest is infamous for? Right now I am limited to solo with the roll bar setup I have...

ARrotard
ARrotard New Reader
1/15/24 11:23 p.m.

Why not just install a MiataCage?

Datsun240ZGuy
Datsun240ZGuy MegaDork
1/15/24 11:53 p.m.

Why? Cause you guys like to party.

Tom Suddard
Tom Suddard GRM+ Memberand Publisher
1/16/24 12:54 a.m.
ARrotard said:

Why not just install a MiataCage?

I put one of those in our last Miata chassis, and loved the kit. And it let one of our drivers walk away from a hit bad enough to red flag the race; they make great cages.
 

But our new cage cost about 1/3 as much to build and is bigger, which is a win/win in my book. 

Driven5
Driven5 PowerDork
1/16/24 11:15 a.m.

I like a lot of the changes, however, the cage in the article still appears to lack any anti-intrusion bars to protect the drivers lower legs and feet from the foot well collapsing in an impact. Wouldn't you want the driver safety cell to protect the whole driver, not stop mid-shin?

 

 

VolvoHeretic
VolvoHeretic GRM+ Memberand Dork
1/16/24 12:07 p.m.

In reply to Driven5 :

As discussed in this thread.

Grassrootsmotorsports.com: Cage Design PSA

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