# NA/NB Suspension Compatibility & Interchange > The NB chassis introduced several geometry and component improvements over the NA. Fortunately, many NB suspension parts can be retrofitted onto NA Miatas! Source: https://help.flyinmiata.com/en_us/nanb-suspension-compatibility-interchange-SkrCYDHHe Last updated: 2026-03-03T22:49:38.868Z The NB chassis introduced several geometry and component improvements over the NA.\* By retrofitting NB parts, NA owners can upgrade their suspension, making noticeable improvements to the chassis and gaining access to a wider selection of replacement parts. * **Modernized Components:** NB parts are often more reinforced and/or utilize more efficient mounting designs (e.g., sway bar end links).  * **A Wide Selection of Shocks and Springs (Coilovers)**: Many aftermarket suspension kits are designed for the NB because they can also be made to fit an NA. * **Increased Track Width:** Using rear NB uprights widens the car's rear stance for improved stability and slightly more aggressive wheel fitment. * **Improved Suspension Geometry:** Reduced bump steer and better caster settings are available through subframe, steering rack, and front upright/knuckle swaps.  _\*NA = first generation of Miata (1990-97), and NB = second generation of Miata (1999-2005). For more clarification about generational terminology, see our article,_ [_What does NA6, NA8, NB, MSM, NC, ND mean?_](http://What%20does%20NA6,%20NA8,%20NB,%20MSM,%20NC,%20ND%20mean?) * * * While many parts look nearly identical, subtle changes in mounting styles and dimensions mean that some parts need to be swapped together to achieve a desirable result:  **Component** **Technical Details** Rear Uprights NB: uprights are 5mm wider on each side, increasing the total rear track by 10mm. Rear Subframe Exhaust hanger locations are different from NA to NB, and the subframe braces are specific to each subframe version (NA8, NB1, NB2). Rear Upper Control Arms 100% interchangeable between NAs and NBs. Front Uprights/Knuckles The upper ball joint stud taper differs between NAs and NBs.  The corresponding front upper control arms must be swapped with the upright/knuckle. Front Upper Control Arms \*See details above regarding the front uprights/knuckles. Front Subframe Requires a matching NB steering rack - recommended to also use NB uprights/knuckles and upper control arms for improved steering geometry. Steering Rack Must match the front subframe.  Power steering fittings and lines differ slightly throughout the NA and NB years. Lower Control Arms Requires matching NA or NB sway bar end link mounts (NA = double-shear vs. NB = ball-joint style). Shock Assemblies NB assemblies fit into NAs, but NA assemblies do **not** fit NBs because the rear upper shock mounts have a smaller access hole. * * * ## NB Upper Mounts One of the most common modifications is swapping NA upper shock mounts for NB units. We do this for all of our NA coilover kits, and even offer [a separate NB shock conversion kit](https://flyinmiata.com/products/nb-shock-conversion-kit). * **Design Difference:** The NA mount is a two-piece rubber-bonded unit (wear item), while the NB is a simpler, stamped steel plate with separate (replaceable) [upper and lower rubber bushings](https://flyinmiata.com/products/nb-shock-bushing-set?_pos=1&_sid=e6828574e&_ss=r). The overall profile of the NB mount is flatter, placing the shock shaft mounting point closer to the upper spring seat than in the NA upper mount design, and the upper spring seat is held tighter to the chassis. The NB spring perches and springs are also redesigned specifically to match the redesigned NB upper mounts. * **Compatibility Warning:** The NB upper shock mount is _not_ recommended for use with NA shocks or springs. NA shocks have a shorter threaded section at the top of the shaft, and the rubber bushings of the later design will not allow for good thread engagement of the upper nut. Due to the bushing stack-up, you're also likely to compromise compression travel, which means you'll spend more time riding the bump stops.  Our NA coilover kits ([V-Maxx](https://flyinmiata.com/search?options%255Bprefix%255D=last&page=1&q=v-maxx) and [FOX](https://flyinmiata.com/search?q=flyin%2527+miata+fox+suspension+for+NA&options%255Bprefix%255D=last)) are specifically designed to use NB upper mounts, which is why we include the NB upper mounts (and bushings, etc.) with NA kits. ### * * * ## Steering and Geometry Improvements If you are performing a deep overhaul, the NB front-end components offer superior driving dynamics. * **Bump Steer:** The NB front subframe, steering rack, front upper control arms, and uprights/knuckles were redesigned to minimize toe changes during suspension travel (bump steer). * **Caster:** The geometry of the NB steering rack position and attachment to the uprights/knuckles allows for more aggressive caster settings, improving high-speed stability and steering feel. * **Manual Racks:** If seeking a manual steering conversion, the NB manual rack is a purpose-built unit that is significantly better than the "rushed" NA manual rack.  However, they are very rare and difficult to find. ### * * * ## Are These Upgrades Worth It? The upgrades are relatively minor, but since NB parts are usually available at low prices and don't require welding, grinding, or machining to fit, they're often considered low-hanging fruit for NA owners looking to make incremental upgrades to their car.  Specifically, the use cases NA owners might be interested in are: * **Access to more coilover options:** Most aftermarket coilover kits (FM and elsewhere) tend to use NB-style upper mounts.  They are simpler to produce and allow the same coilover kit to be installed across a wider range of applicable vehicles (1990-2005, instead of just 1998/9-2005).   * **You want a wider rear track:** Swapping to NB rear uprights is an easy way to gain 10mm of track width without using wheel spacers or swapping to a different set of wheels with a wider offset.  * **You are racing:** The reinforced 2001+ control arms are stronger and better suited to high-load track environments (big sticky tires, stiff suspension, high G-forces, etc.).  * **You need better steering:** Moving to an NB front subframe/rack combo provides the most modern steering geometry available for the pop-up headlight chassis. * **You are lowering the car on a tight budget or within class rules:** Using NB top mounts can provide a drop in ride height, provided you use the matching NB-style bushings and hardware.  You will probably have to get creative with removing and/or trimming the NB shock shaft bushings to fit.  Don't forget about the downside of reduced compression travel (_see the [Compatibility Warning](#section1) mentioned above the NB Upper Mount section_). We really don't recommend this use case, but it is possible if you're willing to accept the downsides for a slight drop in ride height.  Generally, the only folks going this route are those in strict racing classes that prohibit aftermarket parts and accept the compromised compression travel for a lower center of gravity. ### * * * ## ## General Guidance for Compatibility * **Check the Year:** Not all NB parts are the same, and some mid-generation updates may require extra fettling to fit properly or at all. For instance, Mazda updated the underbody bracing several times across the NA and NB generations, and some versions aren't backward-compatible.   * **Mind the Sway Bars:** If you use NB control arms on an NA, you must use [NB-style end links](https://flyinmiata.com/products/nb-and-nc-end-link?_pos=2&_psq=end+link&_ss=e&_v=1.0). The mounting tabs are oriented differently and will bind if the wrong links are used.  * **The Golden Rule of Coilover Compatibility:** If it’s going into an NB, it _must_ be an NB part. If it’s going into an NA, it can be either - but keep the sub-assemblies consistent. You should never mix and match individual parts (shocks, springs, and mounts) unless you understand what changes will result based on that particular combo. The shock shaft lengths, the spring perch positions, the way the spring coils are "clocked" or finished, and the distance between the upper spring seat and where the shock shaft bolts in are generation-specific.  * * * Need a visual aid? Our suspension savant, Keith Tanner, covered this same topic on YouTube: [Miata Suspension Interchangeability: NA vs NB](https://www.youtube.com/watch?v=SkEmgsrJ-Cw&lc=UgwEQ4fudaFSFU7IpY54AaABAg).