Bay Area Miata Drivers
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by alex
A report on the installation and critique of Flyin' Miatas butterfly brace
Entry # 1 (6,542 Views) Posted on March 27, 2011
The Butterfly Effect
To begin, I should say: I was warned. The Flyin’ Miata website specifically states 
“. . .Cars with a stock header will require some trimming to a factory heatshield. 1990-93 cars with stock header and catalytic converters will be a difficult install and may not fit. . .” 
at which I scoffed. I do have an FM catalytic converter on my ’93 so I did, I suppose, dodge that bullet. And I was resigned, nay, eager; to modify whatever “factory heatshield” they were talking about. And, while these issues did rear their ugly heads, they were not the most challenging ones. 
I have installed a few Flyin’ Miata components on my car - the frame rail braces, sway bars, springs, bumpstops and the aforementioned catalytic converter and have always found their hardware well designed and reasonably well manufactured. 
This is not the case with the butterfly brace.  
The first thing I found when I unpacked the parts was that the laser cut pieces have wicked sharp edges. I mean, seriously, sharp enough to draw blood just handling them. I’m a general contractor, I work with my hands and they’re not delicate by any means. I suppose anyone else who works on the car would also have fairly tough hands, but still, a few minutes with a 1 inch belt sander might keep an auto mechanic from getting pissed off at my car and taking retaliatory measures on it. I spent twenty minutes with a file to break those edges. 
I had help installing the brace from a fellow Miata enthusiast who had installed one on his NB. As we held up the parts to see how they were going to sit in there new home we found that the brace was going to come quite close to a bracket that holds a rubber exhaust hanger, so we sketched out a rough shape and used a robust grinder to give a bit more clearance.  
Cutting away the heat shielding wasn’t complicated; we marked it out with a sharpie and cut it away with a Fein tool and a Dremel. We probably put the brace in, and took it back out about 5 times before we got exuberant and really started hacking away at the shield, but it did fit. The center section is about a quarter inch lower than the bottom of the frame rails; it’s going to get scratched. 
My fellow enthusiast’s recommendation was that I should buy some M10 x 1.25 nuts and have them tack welded to the wing sections. He even specified brand and type. Perhaps “enthusiast” is not a strong enough term. In the installation instructions about the accessibility of the nuts, FM says 
“. . . We find it is easier to loosely attach the center section to the wings prior to installation due to the narrow fit for tightening these bolts. You will likely call us names when you go to tighten them as the bolts are a bit tricky to access. . .” (Emphasis added)  
Yes, they are tricky to access because there isn’t adequate access engineered to them. (they mean nuts, no one would put the bolt heads on that side) There is a slot from below so that you can see the nuts but it’s too small to get a wrench through to hold them still. So you’d have to get a wrench up in that spot but the exhaust, transmission and tunnel are also in the way. Tack welding the nuts in place is a reasonable solution, though it may reduce some flexibility in accommodating mis-installed frame rail braces, to which the butterfly brace connects. 
Referring to the Flyin’ Miata site again, they state 
“. . . The fuel lines and rear brake lines are tucked away and protected from impact. . .” 
This is not what I found. 
The brace effectively re-routes those hydraulic lines farther away from their protected spot at the highest point along the inside of the factory frame rail and places them below the front of the brace’s “wing” section. It is not designed to accommodate the nicely curved sweep of the lines, nor is the recess between the wing and the frame rail wide enough to fit the factory brackets that hold the lines in formation. If FM supplied re-designed replacement brackets that would tuck the lines in the slot it would improve their protection. A flat bar with a molded plastic piece that pulled the lines closer together and into the recess between the frame rail and the wing section, screwed to the wing section (instead of the frame rail brace) would improve their safety. I have already ground off the heads of the screws that hold those brackets to the frame rails. Protected my butt. But the worst part of it is where the lines are forced over the bottom of front of the wing section, they’re just sitting out there, waiting to get crushed between the corner of the wing section and anything that happens to be more than about 4 inches tall in the road. They recommend using the free-hanging brackets to keep the lines from rubbing on the brace, which is a good idea, but it pushes the lines even lower! 
They don’t hide this; it’s shown in the pictures of the installation instructions and in this one: 
Why not increase the width of the recess and round off that front corner of the wing? 
Edit--> and the rear! Same issue! 
This is not just an issue with the “1990-93” cars, this affects all of them! 
So, is it worth it? Well, yes. In spite of these flaws the effect of the brace is dramatic. The car feels more solid, period. I know my suspension bushings are 18 years old with 157,000 miles on them; the car feels a little sloppy, “tired” as they say. Much of that is gone now; pot holes are taken in stride, in hard corners it doesn’t feel like the windshield is rotating in a different direction than the roll bar and cowl shake is reduced considerably. 
Fabulous idea, mediocre execution, not the best combination. I prefer the opposite. 
My 2c, your opinion may vary. 
The down-pipe has been a hairsbreadth from the bolt holding the center section to the "wings" since the install. It made contact with said bolt on right turns, when not enough gas is given in first and engine lugs, and when starting the engine, causing an annoying rattle with percussive overtones. I took the car into the local muffler shop and showed them the problem and they fixed it by prying the pipe away from the brace and relieving the stress by heating the pipe behind the cat. Works great!
Comments (newest first)
2011-03-29 22:11:43 from turbo311
My butterfly brace has been on since 2008. I had it installed by self proclaimed Miata king Mike in Phoenix. So I have no idea the difficulty of installation. I have heard about the crazy sharp edges. Originally there were no clearance problems with the exhaust. But it's made contact with the road and speed bumps due to my carelessness. The header heat shield started vibrating against it. Crazy Red here in Sac noticed it when doing my clutch. His solution was to cut out a small part of the brace, not the exhaust heat shield. Anyway, when it was originally installed and to this day it makes a HUGE difference on the NA chassis. Nick noticed it when he drove my car and that made me happy. I love mine, but if you're serious about autox it will move you up into a class that the Miata doesn't need to be in. No regrets for me really :)
2011-03-28 08:32:06 from nick
Wow, after reading this, all of a sudden my car doesn't seem so flimsy anymore. Great writeup, Alex, as usual.