If you own a 1.6L or 1.8L NA Miata, the best upgrades you can make are to the suspension and handling. Making power is costly, so instead of spending money on acceleration, you should upgrade the suspension and handling with components like coilovers and sway bars.
Anti-roll bars, or sway bars, reduce body lean and roll in turns. Reduced body roll improves handling on twisty roads. One of the best handling upgrades for the NA Miata is a set of sway bars, alongside stronger coilovers. This article will explain how sway bars function, why you should install an upgraded one on your NA Miata, and what brands we recommend.
How Sway Bars Work
Sway bars serve as a connection between the left and right sides of the front and back suspension. The vehicle’s center of gravity moves to the right when you turn a bend. This shifts the vehicle’s center of gravity to the right side, causing the right set of tires to exert greater force on the road than the left set. The term “body roll” describes the movement of the vehicle’s center of gravity to the right. As the body rotates, it generates a torsion force.
Sway bars are designed to prevent the vehicle’s center of gravity from shifting to one side. The anti-roll bar twists when the center of gravity moves, shifting the vehicle’s center of gravity back to the other side and reducing the amount of body roll.
The NA Miata’s suspension rigidity may be modified using aftermarket sway bars of varying thicknesses and materials.
Miata Sway Bar Upgrade Basics
When shopping for replacement sway bars for your NA Miata, keep a few things in mind. Thickness, solid versus hollow, and a degree of adaptability should be emphasized. No matter if you want to use your Miata for track days, street driving, autocross, etc., the ideal configuration is likely to vary depending on your goals and intended usage. The topic of endlinks will also be discussed briefly.
Sway Bar Thickness
For the NA Miata, the front sway bar measures 19mm on base models and 20mm on those equipped with the R-package. Cars equipped with the Torsen LSD received an extra 12mm of rear travel compared to the standard 11mm seen on NA8 vehicles produced between 1994 and 1997. In order to strike a balance between ride comfort and responsive handling, manufacturers typically install modestly sized factory roll bars.
It is possible to find aftermarket sway bars for the Miata in widths of 22mm-25mm up front and 14mm-16mm in the back. Sway bars that are hollow, or tubular, typically have slightly larger outside diameters due to the thickness of the piping wall. Bars with a greater thickness are stronger and stiffer, and so have a greater effect on body roll.
A few general rules here on the Miata:
Thicker front sway bar = more understeer.
Thicker rear sway bar = more oversteer.
Since an improved bar creates too much oversteer, most autocross guys go with the factory rear bar. Here is a great resource for figuring out what size sway bar you need for your Miata if you compete in autocross. In addition, many argue that the 16mm is too large for track day competitions since it allows the rear end to swing out too much. It all comes down to setup, but the 14mm and 15mm bars appear to be better suited for the track, while the stock bar is better suited for autocross.
So, I decided to upgrade my NA6 with a 16mm rear bar and see how it performs on the track. But if you aren’t a seasoned and dedicated track man, I doubt you’ll even notice the difference of those extra 1 or 2mm.
Solid vs. Tubular Sway Bars
A sway bar can be made from steel or aluminum. The sway bar can either be solid all the way through or it can be tubular and hollow on the inside. Stiffness and tensile strength are the two most noticeable distinctions. The stock sway bars are solid, so upgrading to a solid sway bar will increase the vehicle’s overall mass. The Racing Beat solid bars add roughly 4 pounds to the front and 1.3 pounds to the rear compared to the standard setup. I was unable to get weight information for competing brands, but I would guess that they are similar.
However, tubular bars have two advantages over solid bars: 1) they are much stiffer and 2) they weigh much less. The tubular front bars are around 1.3 times as robust as the solid bars, according to Racing Beat. They weigh roughly 5.5 pounds, making them lighter than stock (6 pounds) or solid (10 pounds).
Only the front sway bar is made of tubular bars. It’s likely that a tubular rear bar, while strong and stiff, would cause excessive oversteer. For the front end, tubular is favored by many track Miata drivers.
Adjustability
Sway bars on most North American Miatas can be adjusted to varying degrees. There are typically three settings for the front bars and two for the back. Simply put, the stiffness of each bar can be changed via the various settings. The majority of drivers keep the front at the medium position and the back at the lower position for daily driving. Adjustability is not a standard feature of tubular bars.
Sway bars that can be adjusted are something you should look at. To fine-tune your suspension setup, it’s best to have a few adjustable parameters to play with.
Endlinks
The suspension is linked to the sway bars by endlinks. The factory endlinks are quite thin and weak, especially if the bike is 30 years old. After 30 years of use, the endlinks on my new sway bars for my NA Miata were finally worn out, so I replaced them recently.
End links are a necessary part of any sway bar upgrade, but they add around $150 to the total price. If the stock endlinks aren’t fresh new, they won’t be able to handle the increased stress from the strengthened bars.
Best NA Miata Sway Bars
You should know that the NA6 and NA8 models have different fitting requirements. Some brands’ sizing varies from model to model, however I’ll highlight that fact below. To reiterate, the ideal choice depends heavily on the specifics of your system and your own preferences. There are both drivers who want less oversteer and drivers who prefer more oversteer.
You can also modify this by changing the spring and strut rates or using a different coilover. Inquiring with the serious event drivers about the optimal configurations for their tracks and auto-x Miatas is your best chance. Although I do drive a 1992 Miata NA6 equipped with FM bars and MeisterR Club Spec coilovers, I don’t autocross or track often enough to offer an informed view.
- Eibach
- Flyin’ Miata
- Racing Beat
- 5x Racing 14mm Rear
1) NA Miata Eibach Sway Bars
The reason why Eibach sway bars are at the top of my list is because they are the official sway bars for the Spec Miata. The NA6 and NA8 both feature front and rear bars measuring 24mm and 15mm, respectively. The solid construction of the bar means it won’t be as rigid as a tubular alternative, but the 15mm thickness at the back means it should be fine for the track. Because the standard spring rates for Spec Miatas are 700/325, which is quite stiff, these bars should work well with a softer suspension setup for the street or the track.
The front anti-roll bars from Eibach have three different height settings, while the rear ones have two. These are the spec bars for a reason, and they are fairly similar in size and price to our other options, even if I know Spec suspension isn’t the most finely tuned setup for track cars that don’t have special criteria.
2) Flyin’ Miata NA Sway Bars
Front and rear sway bars from FM measure around 22mm and 16mm, respectively, for the NA6, whereas the corresponding measurements for the NA8 are 25mm and 16mm. FM sway bars, in particular for the NA6, are typically configured for use on the street. They’re more comfortable since they’re less stiff up front, but they’re less than ideal for track events because they’re more stiff behind. They’ve got the right amount of stiffness on the NA8.
For regular use, these are the sway bars I recommend. For starters, they offer the best value. They were $299 when I bought them; perhaps the price has increased since then; but, at $120 for the set of four endlinks, they remain a great bargain. In addition, they are less hostile in terms of stiffness, which improves their road comfort.
In general, a good street design. For serious track cars, the NA6’s rear suspension may be too rigid, while the front may be too soft. Overall, a reasonable price given the level of performance and convenience offered.
3) NA Miata Racing Beat Anti-Roll Bars
Tubular front sway bars from Racing Beat are the best choice for your NA Miata. You may also get great sway bars from Racing Beat. Both the front and the back solid bars are 24mm in diameter, while the middle is 16mm. As an added bonus, this setup provides a rear suspension that is slightly more rigid than Eibach’s offering. Both the front and rear tubular bars are 1.125 inches in diameter, and they are supposedly 1.3 times as strong as solid bars.
Tubular front and “racing” tubular bars are available from Racing Beat. The metal thickness of the race tubular bar is.188″, which is significantly thicker than the standard tubular’s.125″. Costs for alternatives with tubing increase by around $50.
The Racing Beat Race Tubular is a great choice for those who like to “go as large as they can” on the front bar. In addition, they have a front sway bar brace kit that is unlike anything else on the market. Though I think highly of the brand as a whole, I have to rank it third due to the frequency with which its products are out of stock and unavailable.
4) 5x Racing 14mm Rear Bar
Oversteer can be prevented with the use of 5x Racing’s 14mm rear sway bar, which can be purchased for $150 plus $99 for the endlinks. When choosing between 14mm and 16mm, the 14mm is the better option for driving on the street or competing in autocross. It’s a sturdy bar that can be adjusted in three different ways, making it an excellent choice for those in search of a discreet tailpiece.
NA Miata Sway Bar Summary
To me, sway bars are the second best mod for the NA Miata, right behind coilovers. Handling and cornering are enhanced by sway bars because they lessen body roll. When choosing the right sway bar thickness and configuration, there are a few factors to keep in mind. Many people think you should have a thick front end if at all possible. Although 16mm versions are available for the back, they are too stiff for autocross and track events. Front bars made of tubing are ideal for increasing rigidity.
Overall, your goals and driving style will determine which sway bar is ideal for you. My NA handles great in town now that I’ve upgraded to the FM NA6 bars and some very stiff coilovers. Since I am not an expert on the track or in autocross, I am not as picky. Sway bars, when added to a factory Miata, significantly improve the car’s handling and cornering. Experts in your area are worth consulting if you’re into racing.
