Ok I have owned my Miata since october. I bought it with the hardtop on it and love the way it drives. Earlier in the year i took the hardtop off and drove it around for a few days and absolutely hate the way it feels with the hardtop off. What will fix that feeling? I have the delrin door bushings already. Is the answer a roll bar, butterfly brace, combination of both?
I would think the butterfly brace from Flying Miata would take the looseness out of it. I don't have one on my Miata , but I have friends that do and they swear by it.
A butterfly brace works great, even if it can be a bit fiddly to install. I'd start there, personally.
A proper roll bar will help a bit as well and improves safety while you're at it. That would be my next step.
There's also the Frog Arms, but those are typically used on the V8 cars to improve torsional rigidity, but I suspect they would have an impact on cowl shake and the like. I'd consult FM on whether it would help enough to be worth it.
Frog Arms are out of production, but we're working on a new and improved variant.
The butterfly brace is going to be the most effective of the options mentioned, as it addresses the weakest part of the car: the connection between the front and rear bulkheads. A set of frame rails is an easier install but less effective option. Roll bars are bolted to one of the stiffer sections, so they have far less of an effect - unless you're upside down. Frog Arms (and their ilk) should help with stiffening the nose of the car, but not by as much as the butterfly.
You don't say what year your Miata is. There is a different rear subframe from the NA6 to the NA8 with more bracing on the later model. Perhaps that swap would help.
My '97 had a tweaked subframe so I replaced it last year. But in my ignorance put one in from a '93 (no place for the U shaped brace). This past winter I replaced it again with the correct one and it is noticeably stiffer.
I also did polyurethane suspension bushings all around at the same time. The car feels stiff!
The fm butterfly brace did amazing things for mine
The rear sub frames gained braces over time, but the best of those mount to the tub. The 1.6 cars don't have the mounting points at the tub, so changing subframes will only get you so much. There are aftermarket braces for the early ones.
Worn bushings will add a lot of slop to a chassis.
Its a 95 m edition. So it seems the butterfly brace is currently in the lead. I will do a roll bar eventually anyway but I am still looking at which roll bar i want for hardtop compatibility, etc so it looks like the butterfly brace will be my next purchase.
I found a roll bar really firmed the "back half" of mine, but mine was rusty when I bought it. I suspect cutting out and rebuilding the rotten sections left it a little floppier than the average clean Miata. As for roll bars, I put an M2 double diagonal and harness bar in mine. I've tried it with a hardtop and it clears pretty easily. I've heard second hand that clearance between a roll bar and hardtop isn't "universal" depending on the particulars of the chassis and the installation, so this is the official "YMMV" disclaimer.
The big problem with using a Hard Core bar with a hardtop is that blocks the side mounting points. The Sport and Hard Core Hard Top (or "Fat Boy") bars clear the hardtop fine.
MrChaos wrote: Its a 95 m edition. So it seems the butterfly brace is currently in the lead. I will do a roll bar eventually anyway but I am still looking at which roll bar i want for hardtop compatibility, etc so it looks like the butterfly brace will be my next purchase.
If you're just street driving the butterfly brace will help. If you're planning on going to the track you'll need the roll bar, so might as well get the door bars too. Their construction & outboard location will give you a more noticeable improvement than the butterfly brace.
I did the now discontinued Frog Arms on my 90. It had just been the victim of a Big Foot attack, as a pickup truck drove over the nose of the car when I was stopped at a stop sign. I thought that at it's age, it needed all the help it could get. Definitely made a difference in the front of the car, took some of the looseness out. There is another company making something similar, but can't remember who. The car isn't the only old thing in this household.
There are a couple of Frog Arm knockoffs out there, and we're working on Strong Arms that will be a step up.
About the door bars - keep in mind that they intrude on the passenger's compartment. We tested a set on one of our cars and none of us were happy with having them share hip space and ankle space with the meat.
Keith Tanner wrote: About the door bars - keep in mind that they intrude on the passenger's compartment. We tested a set on one of our cars and none of us were happy with having them share hip space and ankle space with the meat.
Yup, that's why I mentioned track duty. They are stiffer than the BFB & the front anchor pad is less intrusive to your meat than a cage downtube pedestal, especially with wheelwell bars. Just depends on your priorities.
Keith Tanner wrote: About the door bars - keep in mind that they intrude on the passenger's compartment. We tested a set on one of our cars and none of us were happy with having them share hip space and ankle space with the meat.
+1 on this. I've driven a couple friends' cars with door bars and I can't stand them. Perhaps my butt is too wide, but I don't understand how anyone can drive with them installed. They also get in the way of my left leg when on the dead pedal and take up precious space that's IMHO more useful for a proper FIA seat.
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