When Flex is BAD - Chassis Rigidity (FM Live) 

How many times did I say "noodley"?

As a non-Miata owner… these technical videos are the best! Keep them coming. Been slowly going through all of the Facebook live videos that have been posted and they are by far the most informative and well explained on RU-vid. I also want a Miata more and more for some reason after watching these vids…

Please consider making a companion video to your diagrams for seam welding. Not necessary to actually weld anything, but have the areas uncovered, and talk about prep, after care, and approximate amount of "high effort".

great engineering talk about chassis. this video deserves more views. Not everyone is into miata's tech talk

Great video Keith, chassis stiffening is so underrated - I learned loads, thank you. I have a 1991 1.6 Eunos and funnily enough adding a roll bar helped with the 63mph jiggle. But what really made it disappear was installing door bars; I highly recommend them to anyone with an early 1.6 or even a 1.8. Keep up the great work - it's really appreciated by more people than you might think.

My experience is that an NA Miata, in the condition it rolled off the show-room floor, does not shimmy. If this is true, generally, as it was true for my car, then the closer the suspension parts are to 'as new' condition the more precise the handling, and the lower the chassis vibration will be. Ball joints lose stiffness long before they fail. I replace them every 30 or 40 thousand miles, not because they 'need' to be replaced but because I enjoy the precise handling that factory fresh suspension parts provide. Ball joints cost little and the job is a simple one. Many people seem to delay replacement of the upper front control arm bushings. Often they believe that it is necessary to replace the whole control arm. Moog, however, sells a bushing that presses into the factory control arm nicely. Also, I find that when bushings start to squeak they are ready to be replaced. I have replaced all of mine twice. Rubber hardens as it ages, and old, low mileage bushings will slip rather then flexing. Once they start to do this they wear quickly. I used urethane for a while. Even with Zerk fittings these are hard to keep lubricated, and then they squeak. I am currently using the IL bushings sold by Flyin' Miata, which I like very much. The IL bushings are slightly stiffer than stock, but not as stiff as a competition bushing. Replacing all the suspension bushings is a lot of work. With new IL bushings, new ball joints, fresh shocks, moderately sticky tires, a good alignment, and some chassis bracing you will have a car that is exceptionally nimble, even in comparison to some up-market cars famous for their agility. For chassis bracing, I am using Flyin' Miata's frame rails, a Cannon brace, and Racing Beat's front chassis brace and the Delrin door blocks. Collectively these made an enormous difference.

The factory hardtop makes a massive difference in perceived chassis rigidity over bumps. It and the large rear window are the only reasons I like to run it because top down is more fun.

I wish we had a channel like this for the BMW E46 M3 !!

Helpful technical info. Well explained easy to understand how the Miata structure is. Looking forward to checking out the Flyin’ Miata parts for NA.

Love my FM frame rails, made a huge difference to my NA...cheers from NZ...

Worn out door hinges will negate any improvement you get from the door braces (delrin pucks)

Thanks for another good one!

Great video. I'm going to do a full bare metal resto on my NA and I'm very tempted to add seam welding while I do it.

Very informative

I hadn't realized you wrote those books. I don't know when I was last in a Barnes & Noble, but I remember seeing those books on the shelf, way back before I bought my NA6 Miata.

Thanks, just bought your book after seeing this.

I could not believe how much of a difference the strong arms made on my K-swapped car. Cut down on vibration, and made the whole front end feel like it was doing what it was supposed to do. Frame rails are next!

Great vid! I need one of those flyin miata stickers for my bar. What about the possibility of rust for the frame rail bars?

@Flyin' Miata Does improved chassis stiffness improve the longevity/durability of the car by any noticeable amount? You guys have been working on cars that have been on the road for many years, and I was wondering if you have notice if cars that had stiffness installed earlier in their life were healthier later on?

What in your opinion is the best over all year to buy used? I personally like the looks of the mx-5 I've found a 2008 with 28k for 15k one owner and the fact that they r a little roomier.

Love the idea of adding bracing but when will the butterfly braces be back in stock? They have been out for a while.

Can you comment on the effect of Nielex Pro Spec Knuckle Support on daily comfort/NVH for ND Miata? Anecdotes claim that steering feel/turn in response is improved but can only see real benefits at the limits of grip. Do these support the suspension in a way that allows the suspension to do more of what it’s designed to do and mitigate harshness from transmitting into the undamped spring that is chassis flex?

Thoughts on seam welding just the door jambs? Any tips?

“Because you can never be too stiff” is a perfect example of what she said. 😂

i have the 65mph shimmy in my 99 model, its my 3rd 99 and i didnt have it in my other 2 cars. i wonder since everything runs in cycles at what speed the next occourance above 65mph would be....i would imagine it would be somewhere around 130mph

Enough to own a noodle shop. I noticed these harmonics symptoms at 62 mph and maybe another. I thought I saw the nose dive and hunker down a little more. So could be wrong but I concluded the front lip was designed to work harder as an air dam at faster than "normal" speeds. Bull's wool? 🤔

We're obviously not biased ;) ... BUT, replacing suspension bushings on a vehicle, especially those on "Fun" cars can make such a difference. Ride, comfort, turn in, tyre life, resistance to oil etc (because some cars like to leak) are all benefited by changing to a Polyurethane bush, but even changing for a new OEM rubber bush will be and upgrade from the originals.

Absolutely loving these videos. Which steering wheel is that in the blue NA Miata? And where did you find that blue Mazda horn button? I didn’t see them on the website lol

For a 2001 nb which is the best choice under transmition?

Got a 95 NA8 and see tire and rims being a big factor for the 65mph shimmy (even with new bushings, bearings, suspension, etc.). When having tires balanced at a shop I've found the ideal number is a road force value of 10 or less with 0 being ideal. Roadforce related to the vibration in the tire due to slight manufacturing discrepancies across the tires carcass. Anything more and the wheels and rims transmit the resonance vibration to the rear subframe then into the PPF upto the front of the car.

People on the forums report that aftermarket front subframe braces (for ND) makes a (positive) difference, however, no one has experience with them after installing the butterfly frame. People usually install everything all at once, or front subframes first then butterfly. My question is would having the butterfly brace make it unnecessary to install front subframe braces, or can benefits still be had for both? Also, I also read that the factory front subframe braces are flexible and in an area that is meant to crumple, and that getting into an accident or hitting a curb with stiffer aftermarket ones could cause more expensive damage to the chassis. Can you comment on this please?

I've seen people welding in the extra plate that reinforces the transmission tunnel and some of the metal behind the seats on an NB into an NA. Does this actually do anything for the chassis or is it more of a crash safety thing?

There's probably one more area worth discussing since you mentioned about the front crash bar under the bumper, will adding a torsion bar just before the rear bumper (two points between the rear tow hook) helps in improving chassis rigidity?

If anyone's doubtful it exists, I 100% have the 65 mph shimmy. I've read about and done the hunter roadforce tire balance and that does work for me, for a time, but after 6-8 months the vibration comes back until I get my tires meticulously balanced again. Coincidentally, my NA is missing some braces that I never got around to installing. Might be time to focus on stiffness

I have FM frame rails to install. The problem is the PO has used the rails as jack points and had squashed them flat. Can the offending sections be cut out to facilitate installation of the FM frame stiffeners without weakening the structural integrity.

Did you say that there is an instruction for the areas to seam weld on your website?

Question: if the main contributor to chassis flex is the car being a vert and a roll bar mostly benefits crash safety vs chassis stiffness, would a cage that is minimal (for ingress/egress), that bridges the gap created by the absence of the roof, greatly improve stiffness?

Late comer to this video. This is my first convertible. 2023 ND2 ST. I read the term cowl shake thrown around a lot. What is it? How do you know if you have it? What does it feel like? How does one minimize it? Thanks again

Something I've noticed, having two separate NB2 Miatas, and going with the Flyin Miata butterfly brace each times Is that the V2 brace doesn't provide as much fore/aft rigidity as the V1 did. V1 effectively was a big X brace across the center of the car (makes it more triangularly braced) whereas V2 is more of a box with the front and rear separate cross supports. I definitely have more of the center console-meets-HVAC/dash panel squeak going over bumps in the road from the flex that I don't recall having my previous car. Any chance you guys will put out a template for a cross bar? There's a company called Oshcut that anyone can submit cad plans to and get laser cut metal made and shipped. I'd love to add a cross brace to mine using the existing bolt holes from the dual cross bars and really stiffen it up.

Can chassis flex be beneficial and act to reduce NVH during daily street driving? I remember reading somewhere that Toyota kept with the C-channel frames on the Tacoma's instead of full box frames to maintain flex and articulation while rock crawling. The ND Base model (Sport in the US) doesn't come equipped with the shock tower brace. If I'm looking for max comfort, should I install one? What about all the other braces you mentioned?

From my internet research the best chassis stiffening mods you can do to the NA/NB is anything that braces the car longitudinal like the frame rails, door bars, fender braces and roll bar to some extent. The other braces can help but like Keith said at what point are you just adding more weight to the car instead of benefiting from a stiffer chassis. I would really like to drive a fully seam welded chassis and compare that to a fully braced one to see if there is any noticeable difference.

Pretty sure I have V1 framerails, what are my options for a butterfly brace?

@ flinmiata I've been looking to buy your front tower brace but is not listed on your web site?

Is there any way we can pre-purchase a butterfly brace for whenever you get going with the new manufacturer and they come back in stock? Or is the pricing subject to change?

you mentioned that mazda said the hardtop didn't add much rigidity on the NAs, but would you say this changes with the bolt-in hardtop brackets available now? I'd imagine a hardtop secured with metal brackets is stiffer than one clamped on with the oem plastic latches.

Was just looking to pick up a set of bronze Kogeki 17x8 and saw that they went out of stock. Is there any kind of timeline on the restock? Thanks a bunch!

I have the Paco motorsports strong arms, FM sways front/rear, Koni yellows, FM springs, top-hats, brand new Storm S1's with road force balanced Conti extreme contact sport, upgraded door bushings, Hard dog rollbar, FM shock tower brace, new rotors/pads, checked/torqued all suspension components and I STILL get the 65mph 'shimmy'. About the only bracing left would be the frame rails w/butterfly bracing. Other than that, I am at a loss as to what fill fix it.

The transmission tunnel was mentioned as the main stiffener, but there wasn't any proposal offered to increase its rigidity. Is there any effort in that area?

I recently tracked my "stock" 91 NA. Used sticky tires (Yokohama A052) and 9kg/6kg coilovers. Had great traction and balance with a passenger, but when I drove alone in certain coners the back right wheel lifted and I couldn't get the power down. Is that necessarily a chassis stiffness problem and if yes is there a easy fix for it?

What is the point of the Anti-roll bar in respect of the chassis, also anti- roll bars can be thicker & more robust. With poor constructed roads and potholes. Will the upgrades of making the miata more rigid, be better in protecting the suspension.

When's the FM front shock tower brace coming out? Will it be triangulated to the firewall or is there not enough structural rigidity up high?

What can i do to limitate the mx5 nd rolling? I would like it a bit more flat.

Can't wait for the fall for the V2 frame rails and butterfly brace. This is how I progressed in my build. Delrin door bushings Strut tower bar Paco fender braces 15x8 wheels and ECS tires (game changer) Competition engine mounts Sway bars adjustable end Links and sway bar mount reinforcement block. Dave fab Jack bar Racing beat front control arm brace Canon brace Roadster sport PPF brace (one of my favorites) Now I just installed my rear Koni sports with FM springs. Still have to do the fronts. Lots of other mods that are not suspension and bracing related.

do nb front strut braces fit na's?

what are you guys thoughts on the Hard Dog side rail bars?

Are frame rail braces worthwhile? I have a 99.

Is it possible to somehow leverage the doors or hood to “close the box?”

C70 has entered the chat.

Will Flyin Miata ever return to run the Targa race again

Important for the loser moment of inertia