I'm down to two choices (trying to remain economical), frogs arm or the butterfly brace. I know the butterfly brace is almost twice the price, but from what I've read it seems worth the investment. Any opinions?

The two braces stiffens different areas of the car,determine what part of the car you want to stiffen up and the decision will be simple.

I chose the BF brace,I find there was no need for me to purchase the Frog arms,due to the fact that I will never track the car or attend autox.The BF brace does more for a street car than the Frog arms will.

Neither. Get the frame rails for $200. You WILL notice the difference. Biggest bang for the buck. You don't even need the butterfly brace, and you can always get it after.

Get a rollbar if you dont have one. Thats a two in one, stiffening and safety.

Have you driven a miata with just frame rails and one with a BF brace?

The BF brace makes a BIG difference compared to having just the frame rails.

No, but adding just the frame rails made a big enough difference... This was on a 90 with 240k on it. If the OP wants to drop the extra $$ for the BF brace, he should.

Well then you should not offer advice if you have no experience with the product.Assuming someone does not need the BF brace is pretty lame,especially when you have no experience with it.

If you ever get the chance to drive a miata with the BF brace,do it,then report back and tell us what you think.

hmmm, everything is real good. after all this i'm leaning torwards the butterfly. next question, not to put any type of competition between FM and others, but comparing the butterfly brace to 949racing subframe brace kit ( 949Racing subframe brace kit 90-05 Miata - subframebracekit ) , opinions?

Okay...

Since I don't know **** about the butterfly brace, and you do, how much MORE stiffening does it offer than just the normal frame rails, and is that worth the extra $241. That would probably help out the OP a little more.

The 949 Racing braces are the old BSP braces,those braces stiffen different parts of the chasis,compared to the BF brace.

Just get the BF brace,you will notice it alot more than 949 Racing subframe braces.

ALOT! and it's worth every penny.

Perhaps Keith can chime in for the technical data on the BF brace.

Hardtop makes a difference on my car. Expensive, but... FWIW.

Oh, another +1 for frame rails, even though I have no experience with them whatsoever, I'd pick them over your other choice.

ALOT is not "arbitrarily close" to anything

it doesn't matter which one you start out with, if you are serious about stiffening you will end up with them all eventually anyways. So get the one the wallet likes most this month and next month get another then another and so on until you are "arbitrarily close" to driving a piece of I-beam

Rough seat of the pants feel? The difference between the frame rails and the full butterfly is similar to the difference between stock and the frame rails. That's not instrumented, it's what our customers tell us. We developed the frame rails first, and if the butterfly hadn't made any further improvements we wouldn't have bothered bringing it to market. It's definitely worthwhile.

I've tried to instrument the chassis stiffness increase from the butterfly, but I was relying on the weight of the car to induce sag. I could do that with a stock car. I couldn't get any sag with the butterfly, so I wasn't able to generate any meaningful numbers.

That by itself sounds like good data. Like how boeing is mandated by the FAA to break the wings off a plane and get data on that, but with the current testing set-up they can't break the wings on the 7E7. Sounds like it's good enough

~Mitch

Door bars stiffen more than the butterfly+frame rails.