Friday, May 20, 2016

Project Miata: Installing a Blackbird Fabworx GT3 Roll Bar into "Miss Miagi" - and some Laguna Seca Track Time

Back in January I picked up a replacement to El Cheapacabra, the $600 musty Miata project car that was totaled when an E46 cut me off at an unprotected left. Using craigslist-fu and the insurance payout I was able to upgrade to this lower mile, non-smelly, smooth running '93 while monetarily breaking even on the whole deal. This of course left some room in the budget for upgrades! First on the list were wheels and tires (donated by the wrecked 1990 car) and after replacing all of the coolant hoses and brake pads/rotors/fluid, it was time to install a rollbar and hit the track.

First, let's get the car's name out of the way - Miss Miagi came about as a portmanteau of Miata and Corgi, since this is a black & tan MX-5 and the little varmint that lives in my house and chews up my shoes is a Pembroke Welsh Corgi, also black & tan (and white). Any resemblance to preexisting characters, fictional or non, is purely coincidental.

The whole idea of picking up a cheap first-generation (NA) Miata was to have a trackday ready machine that needed little more than regular maintenance and some cheap 87 octane gas in the tank to start tearing it up. Most trackday organizers, such as NASA, SpeedVentures, etc. do require that convertibles be fitted with an aftermarket roll bar if they weren't so endowed from the factory. Enter Blackbird Fabworx, a local LA-area business that specializes in bolt-in bars for all manner of Miatæ, and oh yeah, they will fab an entire cage for you if so desired.

I decided to go with their popular GT3 model rollbar, not the cheapest option, but certainly one of the beefiest bolt-in solutions on the market. Through friends and online reviews I knew that these were thoughtfully designed, well made, and easily installable in a weekend. After a short conversation with BBFW owner Moti Almagor my bar was on order.

Here's Wally, the enthusiastic little bugger I referred to earlier. He "helped" plenty of times during the install process in my driveway, mostly by squirming perfectly between my feet just as I was awkwardly balancing something heavy and needed to shift my stance to keep from falling. Thanks, Wally.

In addition to the full x-brace spaning the main hoop and backstays, the GT3 comes equipped with a harness bar, mounts for the factory seatbelts, and large spreader plates for mounting to the unibody.

After welding is completed in their Canoga Park workshop, Blackbird sends the bars out for powdercoating, which can be specified in any color of the enthusiast rainbow. I went with Sparco-logo-yellow to match the enamel on this car's steering wheel. What's the point of having a Miata if you can't show it off?

I won't go into a step-by-step guide for installing the bar, since that does indeed come standard when you buy one of these things. I will go through some highlights, a few tips, and "gotchas" me along the way.

It would be easiest to install the rollbar in a car with no top at all, but I was ensured that it could be done with the folding roof still in place. To strip down the interior I lowered the top for more room to work.

With the seats out, and rear parcel shelf bare of carpet, insulation, and plastic, this is about as far apart as the Miata needs to come. No big deal if you have basic hand tools and a trim popper for prying out the round plastic clips that hold the parcel shelf carpet in place.

I found that in order to maneuver the bar around easily, I needed to put the top back up and slide it in from the side. It helped to not latch the top but leave it partially "popped," like a gold chain wearing Corvette owner's collar, for a bit of extra wiggle room. When placed as shown the bar will want to slide forward and down the rear bulkhead, so some sort of temporary retention method is needed while sheetmetal trimming cuts are made.

The easiest method to me seemed to be simple cargo straps, looped around the rear legs and back to the trunk rim. Ignore the spreader pad crushing the wiring harness in this shot - I didn't bolt it down this way - don't worry.

Above is the best photo I could manage of the cargo strap doing its thing. This was also a nice method because as I trimmed the rear hat shelf for clearance, I could gradually take up slack and scooch the bar back, millimeter by millimeter.

Another look at the initial fit-up. You can see the main hoop spreader plates are hanging off the shelf at the front, where they should be far enough back that the seatbelt reel bolts hold them in place at the top.

At this point, out come various trimming tools; a 4-1/2" angle grinder and tin snips seemed to work best. I was able to measure the distance each leg needed to move back at the main hoop and transfer this to a linear dimension on the parcel shelf, in an attempt to be clean and orderly and only trim away as much sheetmetal as absolutely necessary. This parcel shelf isn't a structural panel but I've seen some hacked-up rollbar installations where great swaths of sheetmetal were removed needlessly, and didn't want to doom Miss Miagi to the same rude fate.

Above we can see the progress on the passenger side - partially trimmed just around the backstay tube. That little rubber/jute pad at the bottom was also trimmed to make clearance for the spreader plate. I could have thrown it away entirely, but Ferdinand Mazda put it there for a reason (mass damping to reduce NVH).

The driver's side shelf geometry is a bit different but neither side was difficult to trim neatly. At the bottom right of the above photo we can see the front mounting plate is now snug up against the seatbelt tower and lower rear bulkhead, so trimming is done and the bar is in its final home.

I found that a transfer punch works best for starting the holes needed for the lower main hoop mount. Imagine that - a tool being used for its intended pupose! This step may seem nerve-wracking but is benign and necessary. Just don't screw it up.

Blackbird provides four backing plates to help spread the tensile load from the through bolts and provide some compressive strength to sandwich the stock sheetmetal. This is great from an engineering perspective since it means the bar is far less likely to be ripped out of the chassis in the event of intense loads - as in the weight of the car coming down on it in a rollover.

The rear backstay mounts have their own little backing plates. Again, none of this was difficult, just make sure everything is lined up square and even, and measure twice / cut once.

What's this - a vintage Blue Point (Snap-On) tap & die set? Surely this didn't come with the rollbar - right, it didn't, but it was necessary (or so it seemed) to complete the job. From an installation writeup on I knew that the top seatbelt slider mounting bolts would likely need to be threaded a bit more if they were not fully threaded from the factory, since the GT3 bar relocates these bolts from the car's sheetmetal tower to the welded-on bracket at the node between harness bar and main hoop, and they have to be cut short to work in the new location.

Here's the bolt in question, with unthreaded shank on the left, my partially cut threads in the middle, and OE rolled threads on the right. This is before cutting the bolt down to length. I was about to do so when I noticed that it was a bad idea - the shank / pitch diameter was (as could be expected) smaller than the major diameter of the metric threads, so running a die over the bolt resulted in some stunted half-threads that didn't seem like they would transfer much load at all.

This closeup shows why I was sketched out. over half of the thread face is missing since I'm trying to cut threads into a pitch diameter that was meant for rolled threads - where the metal would be deformed outwards to a larger diameter, vs removing material.

What I ended up doing was modifying the idea of shortening the bolts completely since I wanted to take advantage of the OE rolled threads, but didn't have a fully threaded bolt that could be cut down to length. Incidentally this bolt is a Mazda specific piece with a stepped diameter under the head flange to allow the seatbelt mount to pivot even when the bolt is fully tightened. A fully threaded variant did come on some Miatas, and is available from your friendly Mazda dealer. I'll get some eventually - but for this exercise I used what I had on hand.

In the name of getting to the track with a safe machine, I used the solution above. Stock seatbelt tower bolt spacers stacked up under the rollbar mounting tab to push the locknut down far enough to use the full threads that remained on the end of the bolt. It works just fine since these spacers are designed to be under compression anyhow; it's just not the most attractive arrangement. A longer bolt is a more resilient spring anyway and is less sensitive to variations in tightening torque.

That's almost it for the install. After reassembling the car and towing it to Mazda Raceway Laguna Seca for the Mazda Friends & Family weekend, there were only a few small jobs left. I installed a Halon fire extinguisher on a Blackbird mount just ahead of the passenger seat rails; nobody likes a Car-B-Que at the track. And even though we wear helmets while driving, the rollbar still needed some SFI-rated padding to be safe. I stuck this on and secured it with black zipties, which remained untrimmed - hey, the session was about to start! This gave the car a "Hellraiser" look and I like to imagine that it intimidated some unsuspecting Crosleys or Wolseleys or maybe the one original Mini that was on track (serioiusly, this was the only car we passed the whole weekend with our 1.6 liters of fury).

Apart from a clutch hydraulic system that wasn't quite perfectly bled, the Miagi performed flawlessly all weekend at Laguna Seca. My wife had her first spin and 4-wheels-off experience after Turn 6, with no damage or injury. No harm, no foul - this is how we learn car control at the limit.

With stock suspension but Stoptech Street Performance brake pads and Falken Azenis RT615K tires, the Miata was easily controllable, predictable, friendly, and fast around turns. It did roll quite a bit but nothing that made us feel like we were in a Buick Roadmaster about to lose control or anything nautical like that. The track time was fun and drama free, for me anyhow. I could kinda forget about the car and focus on improving my driving, and that's the fun part! Camping in the state park adjacent to the track was a bonus for the weekend, and allowed the tongue-in-cheek "parking lytez, yo" photo seen above to be staged at dark.

Overall I couldn't have been more pleased with the new (to me) Miata, and certainly with the Blackbird Fabworx GT3 rollbar. There were no issues during installation (except that pesky bolt, but that wasn't their fault). The bar fit extremely well in the chassis and made a noticeable improvement in stiffness; of course there is still plenty of cowl shake over bumps because this isn't a full cage that ties to the front of the car, but overall NVH is reduced. The car doesn't feel like two halves of a pretzel trying to twist back up anymore. And of course, in the event that the shiny side goes down, we will be much more likely to survive.

I put together a quick video of a few track sessions from the weekend, recorded with my genuine SJCAM SJ4000 (accept no subsitutes). This was posted earlier on DT but is included again here so you, dear reader, can get a sense for the sprightly, smooth, yet not so fast experience that is driving a mostly stock NA Miata around a fantastic road course like Laguna Seca.

Stay tuned for further adventures of Miss Miagi - next up will be real seats and racing harnesses to compliment the roll bar, enhance safety, and keep us firmly planted while pulling g's. Check out the other DT Project Cars here in the Project Car section. This has also been another episode of CFLOMOTO, a corner of DT meant for sharing tips, tech, tricks, and tales of mechanical cunning (and failure).


CFlo is Daily Turismo's co-founder and Technical Editor. He should really sell a few project cars and get out on the track more often.


  1. Nice write up, CFlo, and very nice installation. I was wondering if the padding you added makes the rollbar safe for non-helmeted use? It is the one thing that I dislike about traveling in my buddys' track-prepped cars: the idea of smashing my brains out on their rollbar while picking up groceries.

  2. The new badges need to be made into a t-shirt: 100x100 on on the front, 800x800 one on the back!

  3. Loving the lengthier write-ups by CFlo, please keep 'em coming!

  4. Good job going with the Blackbird bar! He was not making them when I bought my HardDog, but will grab one from him next go around. Fantastic quality, and I love supporting the little guys.

  5. Thanks for the feedback. Bob, the rollbar isn't exactly safe with the padding since my head protrudes above the stock Miata seat headrest. If I were going to keep the stock seats I'd install some kind of additional headrest. The worst situation would be in a rear end collision where the driver's & passenger's head would snap back into the bar. My fix is going to be proper racing bucket seats that will have full headrests all the way up, and harnesses for track use.

    Miss Miagi t-shirt - interesting proposition...


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