RoadsterSport 4 Piece Complete Underbody Ultralight Aluminum Brace Kit for MX5-ND
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RoadsterSport 4 Piece Complete Underbody Ultralight Aluminum Brace Kit


Honeycomb Tubular Ultra Light and Strong, Made in the USA, and LIFETIME Warranty!

PART NUMBER: 61-1839



Price: $699.00



Free shipping offers apply only to destinations within US Lower 48.

Price: $699.00



Free shipping offers apply only to destinations within US Lower 48.


The BEST Complete Underbody Brace Kit for the ND Miata and Fiat 124 at an amazing price. Not the cheap stuff made overseas, these are made here in the USA, all TIG welded, featuring an ultra light and stiff honeycomb tubular aluminum shaft construction for lowest weight WITH strength. Entire kit is just 13.1 pounds, and we are replacing two stock braces that don't connect near as many points nor near as far side to side and front to rear. Result: unlike the other brands this setup includes a Lifetime warranty!

2016+ MX5: Fits manual transmission only.
2017+ Fiat 124: Fits both manual and automatic transmission.

Easily the best VALUE in a full underbody brace setup for ND generation MX5 chassis (some competitors are cheap and heavy STEEL that will scratch and rust quick). All made in the USA, not the China stuff the other brands are selling that often breaks.

BRIAN'S APPLICATION NOTES: See our Forum install thread, this one takes some work to install but average Joes can do it. One large X brace at the middle of the car is far stiffer than the flexible factory sheet metal stock X brace and extended so it connects to the forward K brace and the rear triangle subframe braces, numerous additional connection points for a much more stout result. Rear triangulated suspension braces provide more consistent, linear, predictable rear suspension response.


FIAT 124: We long had this listed as manual transmission only, but customer Bryan at NGEN has now installed successfully on Automatic, no extra bits needed - see pic bbelow:


RoadsterSport Rear Shock Tower Brace




Customer Reviews

RoadsterSport 4 Piece Complete Underbody Ultralight Aluminum Brace Kit

Very noticeable improvement in chassis, even to someone without track experience. Significant improved nvh.I did this at home with a small lift in about an hour. Well worth the investment.

This brace really tightened up the car. Steering weight seems heavier, but more controlled. For the two bolts that are too short I swapped them with two bolts from the oil pan skid plate as they were longer. Pretty easy install if you take your time to check fit before pulling bolts. Way better bracing than the stock thin aluminum.

This absolutely transforms this chassis. Rear end feel is much improved, cabin noises are gone, ride quality it so much better.

So it's a very nice set of high quality pieces.

My only complaint was the mediocre hardware included. I felt like for a few of the bolt there was not enough thread engagement for what this brace is doing to the car.

I went to the hardware store and bought really nice stainless fasteners and proper washers that were longer so the bolts would be in more that just a few threads as it would have being had I not..

100% worth it, if you have any doubts while installing the bolts. Just go to the store and get the correct length fasteners.

Would recommend

I just installed the 4 piece underbody brace and replaced my strut tower brace with the cobalt brace. I had already done several mods including adjustable front and rear Roaster Sport sway bars. The ONLY complaint I have about the brace kit is ZERO instructions. I have LOVED the bits and pieces that I have purchased from GoodWin... Hood Louvers, Carbon Miata Grill, and full quilted Mats, Verus rear diffuser and of course the Roadster Sport Race muffler (plus cobalt pedals) the combination has transformed my 2020 RF GT into something ready to attack any stretch of road. More power would be welcome when it becomes available. The very 1st thing I did was better tires and the exhaust followed by the sway bars.... I believe those are a "must" .... but every addition has helped.

I too found that I need to install two bolts into empty holes... took 20 to 30 minutes to figure out that those bolts and nuts were designed for that purpose.

Had my favorite local custom shop install this complete under chassis brace kit along with the front subframe replacement braces. These could be installed at home with the car on ramps or jack stands, but it was so much easier with a lift.

We ran into a problem only at the very end of the install when attaching the rear triangular braces. The rearmost attachment point is to a blank hole in the chassis channel with no apparent way to secure a bolt. We were further confused by two large silver bolts and washers (about 14mm) that Goodwin supplied with other bolts we had already used in the installation. (Turned out those bolts and washers aren't used at all)

My car was originally sold in Colorado and had undercoating that hid some of the holes in the chassis channel. It would have been less confusing if we had known the holes were there. This was on a Friday early afternoon in Texas. A quick call got Greg on the phone at Goodwin in California. We tried to explain the situation. Greg went out to the shop to ask the mechanics. Long story short, after some back and forth we were made aware of the hidden holes and the two strange long metal brackets with attached nuts and bolts that were supplied with the braces. Those brackets weren't brackets at all but were extensions to send the attached nuts into the channel for attaching the triangle brace.

Thanks so much for Greg hanging with us so long on the phone to solve the problem and even staying on the phone with us until we told him we had it working fine.

I'm really pleased with this chassis stiffening. I push my car hard where I can safely do so. This, along with my other suspension mods has transformed my Abarth into a real canyon carver that's still comfortable as a daily driver.

Amazing brace!

It was a rather medium difficulty level task. Make sure you have some deep sockets and a torque wrench. I had to raise the car on 4 jacks high enough to be able to work underneath the car. Removing the factory bracing is easy enough.

When installing the new brace kit, it helps to start with the middle X brace that way you can align the rest of the braces properly. When installing the front brace to the middle X brace, the bolts that came with the kit were not long enough. However, after a quick email with the GoodWin racing team they sent the correct length bolts.
Everything ran smoothly after that.

Check the forum instruction guide to see how to install the rear brace as you will need to slip the included metal strip piece that has a bolt welded to it through the frame. It is really easy but the picture on the forum will help you shape the metal piece so it slips in nicely and flushed.

My goal was to tighten down the car's chassis so that it would communicate better with the driver. Goal achieved!

The car reacts much quicker and sharper with every input. I can "feel" every point of the car through transitions. The responsiveness of the brace kit is absolutely amazing! The car no longer feels sloppy through turns but extremely nimble.
Especially in the rear, you can slide the rear out and predict exactly what it is going to do and not be afraid to step it out.

The suspension works less and it is absolutely noticeable on hairpins and high speed sweepers as the responsiveness allows you to point and shoot the car through corners.

Brace kit installed along with front sub-frame brace, Cobalt 3-point shock tower brace, and roadster sport rear shock tower brace.
Car is a Club ND with only the mods listed here.

Worth the buy!

This is the ULTIMATE product if you want to increase chassis stiffness in order to successfully track your favorite spider without the need to install -race only- coilovers or shocks that makes everyday driving utterly uncomfortable... No disadvantages easy to install.. Good job Brian!

This underbody brace kit arrived in perfect condition (was well wrapped & boxed). It was very easy to install overall (taking about an hour total). The strutural rigidity and support that this kit gives completely transforms the MX-5 into feeling like a full frame car! I combined this kit with the front and rear Roadster Sport upper strut bars and Delrin door bushings... and now it's like a completely different car!! Beautiful, lightweight aluminum oval tubing makes me want to look under the car just to see it!
Thanks to everyone at GWR for the great products, and exceptional advice and service!

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