Modifications that improve the handling and ride quality of the suspension are the greatest bet for any NA Miata, 1.6L or 1.8L. Rather than spending your money on power, we suggest upgrading your suspension and handling with components like coilovers and sway bars.
Anti-roll bars, or sway bars, reduce body lean and roll in turns. Having less roll allows for sharper turns and improved handling on curvy roads. One of the greatest handling upgrades for the NA Miata is a set of sway bars, together with stronger coilovers. This article will explain how sway bars function, why updated NA Miata sway bars are helpful, and which manufacturers we personally suggest.
How Sway Bars Work
Sway bars serve to link the left and right sides of the front and rear suspension. The vehicle’s center of gravity moves to the right when you turn a bend. Because of this, the left tires are lifted off the ground while the right tires take on more of the load. “Body roll” describes how the car leans to the right as a result of its center of gravity moving. When you roll your body, you generate a torsion force.
Sway bars are designed to prevent the vehicle from leaning to one side and to restore proper balance. When the center of gravity moves, the anti-roll bar twists and redistributes the vehicle’s load to the other side, thereby reducing body roll.
Aftermarket sway bars for the North American Miata (NA Miata) vary in thickness and material, each of which modifies the suspension’s stiffness in its own way.
Miata Sway Bar Upgrade Basics
Adding aftermarket sway bars to your NA Miata requires some planning. Thickness, solid vs. hollow, and adjustability are the primary points of discussion. The optimal setup for your Miata will be determined by your intended use and driving style, whether for track days, street driving, autocross, etc. We’ll talk briefly about endlinks as well.
Sway Bar Thickness
The front sway bar on a conventional North American Miata is 19mm and on an R-package Miata it’s 20mm. 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 good balance between ride comfort and responsive handling, manufacturers typically install relatively tiny factory roll bars.
The front end of aftermarket Miata sway bars is between 22 and 25 millimeters, while the back end measures between 14 and 16 millimeters. The wall thickness of the pipe forces hollow sway bars to have slightly larger diameters. The larger the bar’s thickness, the greater its strength and stiffness, and the greater its impact on body roll.
A few general rules here on the Miata:
Thicker front sway bar = more understeer.
Thicker rear sway bar = more oversteer.
To avoid excessive oversteer, most autocross racers opt to keep their rear bars at their factory settings. Here is an excellent resource for determining the appropriate size of sway bar for your Miata if you plan on engaging in autocross competition. Also, many argue that the 16mm is too large for track day competitions since it allows the rear end to swing out too much. The answer depends on your setup, however a 14mm or 15mm bar is more suited to the track while a stock bar is better for autocross.
I’ve installed a 16mm rear bar on my NA6 and am looking forward to seeing 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
The sway bar can be made from steel or aluminum. Sway bars come in two distinct forms: those that are solid all the way through, and those that are hollow inside the tube. The two most distinguishing features are their respective strengths and rigidities. When compared to the hollow original sway bars, a solid aftermarket bar will provide significant heft. 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 obtain 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. As reported by Racing Beat, the tubular front bars are around 1.30 times as strong as the solid bars. They weigh roughly 5.5 pounds, making them lighter than stock (6 pounds) or solid (10 pounds).
The front sway bar is the only one that can be replaced with a tubular bar. Oversteer would likely occur with a tubular rear bar due to its strength and rigidity. Tubular is a popular choice because many track Miata drivers advocate making the front end as rigid as possible.
Adjustability
Most North American Miata sway bars are adjustable to some degree, but not all. The front bars typically have three settings, while the back ones have two. The various parameters have a global impact on the rigidity of each bar. It’s normal practice to set the front to its midway position for daily driving and the back to its lower position. Bars made from tubing are rarely modifiable.
Sway bars that can be adjusted are something you should look at. It’s much easier to fine-tune your suspension if you have a few options to play with.
Endlinks
Sway bars are attached to the suspension through endlinks. If your stock endlinks are 30 years old or more, they are probably narrow and not very sturdy. My NA Miata’s original sway bar endlinks finally gave out after 30 years of service, so I had to replace them last week.
Sway bar end links are an essential part of any upgrade, but they add around $150 to the total price. Unless they are brand new, the factory endlinks will break under the added stress of the stronger and stiffer bars.
Best NA Miata Sway Bars
Remember that the NA6 and NA8 models have different fitting requirements. Some brands’ sizing varies between models, but I’ll make that clear in the next section. Again, I’ll stress that the ideal choice depends heavily on specific circumstances and individual taste. More oversteer on the track is acceptable to some drivers while it is unacceptable to others.
There will also be an effect from the coilover or spring/strut setup you use. The greatest advice for constructing a track or auto-x Miata for competition is to talk to serious event drivers. Although I do drive a 1992 Miata NA6 equipped with FM bars and MeisterR Club Spec coilovers, I don’t autocross or race on a regular enough basis to offer you a solid recommendation.
- Eibach
- Flyin’ Miata
- Racing Beat
- 5x Racing 14mm Rear
1) NA Miata Eibach Sway Bars
Since these are the Spec Miata sway bars made by Eibach, they are at the top of my list. NA6 and NA8 models share 24mm front and 15mm rear bars. 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. The 700/325 spring rates used by Spec Miatas are quite stiff, so these bars should work well with a softer suspension setup for use on the street or on the track.
Anti-roll bars from Eibach can be raised to one of three heights in the front and two in the back. These are the spec bars for a reason, and they’re fairly similar in size and price to our other options, even though I know Spec suspension isn’t the most fine-tuned configuration for track cars that don’t have certain criteria.
2) Flyin’ Miata NA Sway Bars
The front and rear sway bars from FM measure around 22mm and 16mm, respectively, for the NA6, while the front and rear sway bars from the NA8 measure around 25mm and 16mm, respectively. FM sway bars, in particular for the NA6, are typically configured for use on the street. They’re less stiff up front for increased comfort, but they’re a little stiffer than optimum at the back for sprinting. They’re suitably rigid everywhere on the NA8.
In my opinion, they are the best sway bars for daily drivers. For starters, their price is the lowest of any of the options. Perhaps the price has increased since I purchased mine for $299 (at which point it was a steal at $120 for all four endlinks), but even at that they represent excellent value at little under $500. Second, they’re a little less hostile in terms of rigidity, which makes them more travel-friendly.
In general, a good street design. For serious track cars, the NA6’s rear suspension may be too stiff, while the front may be too supple. A reasonable price for 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. Rear and front sway bars from Racing Beat are both of high quality. The fronts of solid bars are 24mm in diameter, while the backs are 16mm. A rear suspension system that is slightly more rigid than Eibach’s. 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.
There is a tubular front bar and a tubular “racing” bar available from Racing Beat. The metal thickness of the race tubular bar is.188′′, as opposed to the standard tubular’s.125′′. Options with tubing run around $50 extra.
When you want to “go as large as you can” on the front bar, the Racing Beat Race Tubular is the way to go. In addition, they have a brace kit for the front sway bar that makes it even stiffer, which is something no one else provides. Overall, a wonderful brand with great products, however they are frequently out of stock or on backorder, so they only come in at #3 on my list.
4) 5x Racing 14mm Rear Bar
Oversteer can be mitigated with the use of 5x Racing’s 14mm rear sway bar, which can be purchased for $150 plus $99 for the endlinks. It’s well knowledge that 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 who want a less obvious back support.
NA Miata Sway Bar Summary
After coilovers, sway bars are my second-favorite non-turbo Miata upgrade. Body roll is decreased by sway bars, which benefits handling and cornering. When choosing a sway bar, there are a few factors to keep in mind, including thickness and design. Many people have faith in the wisdom of making the front as thick as possible. The rear is more situational, with some 16mm alternatives being too stiff for autocross and track events. Front bars made of tubing are ideal for increasing rigidity.
In the end, your needs and preferred driving style will determine which sway bar is best for you. My NA handles great in the streets now that I’ve installed the FM NA6 bars and some very stiff coilovers. However, I am not as picky because I am not a specialist on the track or autocross. The overall handling and cornering of a stock Miata will benefit greatly from the installation of sway bars. Talk to your neighborhood gurus if you’re like racing.
