butterfly & rail braces revisited

[Keith]

Im a newbie to MX5s. Ive read lots about the FM frame rail/butterfly braces for NAs, but some is posted on sites who are trying to sell these parts. I read on one thread that last year about 5 or 6 members of the forum did a group buy & bought some and had a few dodgy days fitting them. I was wondering what your impressions of the braces are now that you have had them on for a while, the pros and cons, and if you would recommend them? I want the car to be set up for fast street/occasional track and so far I have konis, king coils, adjustable heavy sway bars and camber adjusting upper A arms fitted, and the car set up by East Coast Suspension with. neg 3 deg rear, neg 1.5 deg front camber. Im wondering iwhat is the best way to stiffen the chassis?

[tbro]

Hey Keith,

I think you will find that chassis bracing depends on the model you have, is it a NA6 or NA8.

The latter already has most of the brace work from the factory.

You will get lots of different opinions as to what works and what doesn't.

In my case, our clubman is fitted with a TB roll bar and I found that that stiffened up the chassis and stopped
a lot of the chaddering through corners. I also fitted a front strut brace and brake stopper, as to whether this
really works, who knows but the brake stopper definitely does. I still get some shuttle shudder through rough corners
but I don't think you can do much about this.

So welcome to the obsession and keep ya wallet open.

Terry

[Keith]

Thanks Terry. Ive got a Dec 91 build NA6, which feels pretty "flexible" now Ive done the suspension. The two fore-aft chassis rails are in real good condition- no speed hump damage, but the chassis structure feels flexible -if thats the right word. "Squirm" might be better to describe it under hard cornering, almost as if its twisting slightly. These are only subjective impressions, of course.

You raise an interesting point- the role of the various available chassis stiffeners for front and rear end, which I hadnt really considered as I was only thinking about the Flyin' Miata butterfly and rail braces. Ive seen various braces advertised- some tubular, some cast and some fabricated- for the front and rear ends. It seems to me you could add a LOT of weight if you werent real careful; the 64 dollar question is what works best for the weight involved, I guess.

[marcusus]

If I remember correctly, the only MX5s that had any factory bracing was NB8B and upwards, so having a NA6 or a NA8 will mean you can still get the FM brace. You'll need to wait for some of the other members with NAs to confirm that, but I seem to recall that being the case.

As for the braces, they're great. The car's definitely stiffer, but I only noticed it for street driving. Ride comfort is improved significantly because of the extra rigidity, but that's about all I could really notice. When I went to the track with them, I didn't notice any handling gains. The only down side is that you need to watch how low you install it. There's a possibility of it doing some scraping on speed bumps, but at least it's only the brace rather than something important under the car.

[Fatty]

If I remember correctly, the only MX5s that had any factory bracing was NB8B and upwards,

incorrect. you're probably thinking of the spiderweb / tunnel brace that was introduced on the nb8b. but there was plenty of other bracing introduced earlier throughout the life of the na / nb.

[marcusus]

incorrect. you're probably thinking of the spiderweb / tunnel brace that was introduced on the nb8b. but there was plenty of other bracing introduced earlier throughout the life of the na / nb.

Sorry, let me reword.

The NB8B and upwards are the models of MX5 that don't gain a noticeable improvement when fitted with an FM Brace since they already have something similar. I'm not 100% sure if they can actually be fitted with them either, but a simple visit to the FM site will tell you the info.

[Boags]

Sorry, let me reword.

The NB8B and upwards are the models of MX5 that don't gain a noticeable improvement when fitted with an FM Brace since they already have something similar. I'm not 100% sure if they can actually be fitted with them either, but a simple visit to the FM site will tell you the info.

I know what you are saying; so don't take this as an attack.

I would describe the bits bolted to the bottom of the NB8B as making very little improvement. They are flimsy and I think the butterfly brace would be a vast improvement.

If I had to remove them to fit the butterfly brace it would be no great loss IMO.

Boags

[oongie]

Has anyone compared the autoexe chassis braces to the FM ones?
One seems tubular and the other machined, I am thinking about extra bracing for the NB also...

[Fatty]

boags when you say the oem parts "are flimsy" - have you actually handled them or are you going by appearance?


those autoexe braces look interesting, i wonder if they fit the NA also?

[marcusus]

I know what you are saying; so don't take this as an attack.

ZOMG! Personal attack! Ban!

Where are the rest of the forumites that went in on the buy? I'm surely not the only one about...

[Alex]

I'm still around but my opinion hasn't changed to before
Pros - stiffen the chassis, don't have to worry when scraping since you know it's the butterfly brace
Cons - extra weight (I didn't notice any difference), might have clearance issues since the lowest point will be about 1cm lower, more if your exhaust is low in the middle. drilling lots of holes in your car

would I recommend it, in your case no, well at least not until you have a rollbar put in, if you still want more after that then look at the FM brace

[Keith]

Thanks Sm. Ive got the Brown Davis roll bar, cusco front strut brace/master cylinder brace. . I thought the FM brace might stiffen the chassis up a bit more and benefit handling, but I have not dríven one so I was really wondering if owners feel them worthwhile. Cheers, and thanks for the posts.

[marcusus]

I really don't think there's any benefit to handling. Not that I can notice anyway. Things are definitely stiffer, but on the track I didn't notice it staying more rigid. That being said, I daresay it does do something, and that I just didn't notice because I was too busy concentrating on just doing my lines correctly.

[Mactype]

These definately make the car stiffer although I still question having the centre bracing as I perceive the frame rails do the bulk of the work.

After fitting a hardtop to what was a standard car and getting quite a few creaks and groans out of it, I've noticed the noises became less with the fitting the roll bar and have basically disappeared with the butterfly brace fitted - so it is stopping flex. I think the seat of the pants results will depend on how else the vehicle is setup, a roll bar does appear to stiffen up the chassis quite a bit.

Also have a look at your existing frame rails, I think that in a vehicle that has these flattened you'll get more out of the FM rails than in a vehicle that has pristine rails - FWIW with the FM rails installed its also quite reassuring to know that when going over those largish speed humps the rails aren't flattening anymore.