There are a LOT of built road-racing 1990-2005 Miatas, many sporting “Spec Miata” decals but many others with a whole mix of things. SSM, ST6, STL, etc. What do they all mean?

I’ve said it a few hundred times on this blog: Spec Miata is THE biggest Road Racing class in America, this brings with it certain advantages. A huge knowledge base, lots of support from both Mazda and the Aftermarket, but most of all: OTHER PEOPLE TO RACE. Spec Miata is raced in the two of the largest road-racing clubs (SCCA and NASA), but also is raced in a bunch of local series across the country. Later in this post we’ll go over the differences in rules between clubs as well as the different sub-classes of Spec Miata. 

Henry Ford is largely credited with the quote: “Auto racing began 5 minutes after the second car was built.” What is Auto racing without other cars to race? I can imagine that nothing is more frustrating than showing up to race and being the only car (Unless you want to boast on Instagram about “winning” a class vs yourself… yes, I’ve seen it) While there is plenty of varying popularity between regions, it’s fair to say SM is almost always one of (if not THE) largest groups at club race events. In Spec Miata you aren’t running with 1 or 2 cars, Even a rare “dead” region still has a handful. 

You may see very similar looking Miatas running in other classes such as SM2, SMT, ST6, ITS, or STL. There’s a couple reasons for this: 1) Drivers are looking to maximize the amount of races they can run in a weekend. Running in a second class gives them the opportunity to race twice as much. 2) With Spec Miata being such a huge class, there are a lot of forces behind making and maintaining the rules. With top-down rule creation you’ll occasionally have people getting frustrated about specific items, often directly related to budgets. Since there are SO many people racing SM, it’s pretty easy to create a sub-class and immediately have people to run with. That said, individual popularity of these offshoot classes varies a ton: You can’t expect to see a regular SM-Size field most of the time, but you may be in a region where an offshoot class is more popular than the standard SM.

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The most questions I get about the different classes are from people looking to buy a Spec Miata, and unsure if a not-quite-sm car should be considered. While a car with SM2 on the door will likely be a “standard” Spec Miata, one with “SSM” might have a considerable disadvantage in a field of competitive SM cars. Of course, a SSM car can be brought to standard SM spec, but that’s gonna cost more money.

If a car has ST6, STL, ITS and SM on the door, it’s likely a legal SM. But if a car only has STL, ITS, or ST6… It will likely have a handful of modifications that take it out of SM legality, some which could be very significant to change.. 

I’m doing my best to make sure this information is accurate at the time of posting and will work frequently to update this… but class rules change often so double-checking specific rules for a class or organization is always a good idea. That said, if you do see any errors, missed or outdated info, leave a comment and let me know!

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SM – “Standard” Spec Miata, this is the main class. SCCA and NASA are the two largest Spec Miata clubs and their rulebooks are largely the same. The required Spec Tires (NASA on Toyo Vs SCCA on Hoosier) are the largest difference, but we’ll discuss some more small differences below.

SM2 – Spec Miata, following the standard SM rules but ONLY for NA (90-97) cars. While the general SM rulebook is about as well balanced as it can be, it’s still a whispered secret that the NB’s may have an advantage on most tracks. The SM2 class gives the flippy headlight Bois a place to play by themselves, ending that debate.

SMSE Similar to SM2, SMSE is a Southeast regional class similar to SM2 but it is 90-93 1.6 only.  Excluding all 1.8 cars (even the 94-97 NA’s). 

SMT – SCCA “Spec Miata Toyo (or Tire…or Touring)”. This is standard Spec Miata, but running Toyo Tires (like NASA) instead of the standard SCCA Hoosiers. SMSE also has a SMSE-T Variant of 1.6 cars on Toyos. 

Tires are a huge part of anyone’s racing budget and are the target of several different rules and initiatives to fix. While the Hoosiers offer some incredible grip, they are largely understood to start dropping off with each use, forcing drivers to constantly buy tires to stay competitive. Toyo RR’s on the other hand offer significantly more usable heat cycles and are a favorite of many budget racers, so the SMT class was born. 

*Toyo stepped up to offer the same contingency prizes as Hoosier does for standard SM for SMT racing with SCCA

SSM – SCCA “Showroom Spec Miata” This is one of the farthest deviations from the “standard” SM rulebook. SSM allows only 90-93 1.6 cars (Some 1.8 cars were grandfathered but are no longer allowed as of 2023). Regional and based largely in the Washington DC/Mid-Atlantic but there are some other regions who participate as well.

This extra limited rulebook in a class with an already limited rulebook goes that bit further to keep costs down. Each of the little additions allowed in standard Spec Miata add up to making it a much more expensive class than it was at its start.  While buying a brand new, top tier Spec Miata can (somehow) cost nearly $70,000, a brand new top build SSM would be significantly cheaper. 

The class has a process where cars are dynoed and the engines are sealed. They have spec spark plugs, spec exhaust, run on bilsteins, etc. The spec tire is the Toyo RA1, While they are disappointingly overpriced, they are famous for outliving most of the cars it’s attached to, wearing like iron while providing reasonable grip. A Treaded tire, drivers often have a shaved set for dry competition and retain a fresh full-tread set for rain races. 

ST6 – NASA’s power-to-weight class. A Spec Miata built absolutely to the edge of the SM rulebook (including horsepower) should still fall pretty neatly into the ST6 category. A Purpose-Built ST6 car would definitely have an advantage over a Spec Miata, but ST6’s popularity and prep level varies by region. 

TT6 – NASA’s Time Trial Class runs the same classing structure as ST6, but without the full safety equipment requirement of road racing. A bone-stock streetcar can run in Time Trial, as can a full Spec Miata (as long as they get the dyno to prove that uh… it’s a Spec Miata, and fill out a redundant class form). Similar to ST, a car with only TT6 on the door could be a full on Spec Miata, but (with TT) it could also be a stock street car. NASA’s old number TT classes were phased out a few years ago, something with a TTD/TTE decal probably hasn’t raced in a while.

STL and ITS and others- A few SM “similar” classes in SCCA racing, they are frequently populated with a significant portion of Spec Miatas looking to double-dip and get extra races in a weekend. As with ST6, a Spec Miata has significant disadvantages to a purpose-built ITS or STL car, but the extra race time is still valuable and fun (And the classes may even be populated only with Spec Miatas on a given weekend anyway). I call these classes SM “similar” because they’re similar builds with similar cars, capable of similar lap times, but they allow many different modifications than the very narrow Spec Rulebook. 

With all of these “SM Similar” and “Catchall” classes (And I know i’m missing some):  Some changes between the classes can be made easily (like changing tires and removing a wing), but with rulesets coming from totally different direction/intention, there may some huge pieces that could prevent a STL or ITS car from being legal in Spec Miata. Things like upgraded suspension bushings and modified control arms may be allowed in open classes, but are illegal in Spec Miata. While a new camshaft or aftermarket ECU is legal, neither are allowed in Spec Miata. Some of these cars are gutted and cut up well beyond what is legal in Spec Miata. If purchasing a car not billed as a “ready to race” Spec Miata, pay close attention to exactly what was modified. Often, the work required to bring a ST6 car to Spec Miata legality would cost WAY more than just finding a Spec Miata or even building a fresh car.

There’s certainly many classes and opportunities I’m missing here, especially regional classes (For example, my region’s NASA GTS allows cars from all manufacturers, not just “German” that the class is named for. So a SM should be eligible for GTS1 also). As I mentioned earlier, the popularity of these other classes can vary largely between regions and even between events within said regions. For Example, there are usually enough ST6 cars in NASA Great Lakes to fill a podium (with a couple races near 10 cars), but there aren’t any ST6 regulars in the Northeast. 

*CSP, XP, ES, WTF, E2, ETC: There are a LOT of ways you can go driving or racing in the world. Know you may see cars with all sorts of various class names on the door, expect to see a little of everything in the wild (Including classes that may mean one thing in road racing and be a completely different type of class in autocross).

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WHERE can I race?

SCCA and NASA are the nation’s two largest club spring racing organizations, and Spec Miata is the most popular class in both clubs. While each individual region of each club may be totally different, SCCA and NASA tend to draw pretty different crowds and everyone usually finds a place where they feel like they fit in.

As I mentioned before, while Spec Miatas can very easily crossover between SCCA and NASA there are some small differences: In Short – NASA is more strict with Safety gear requirements, and SCCA is more strict with modifying NA chassis cars. However the differences are small, the vast majority of current Spec Miatas could cross between clubs in their current state.

*To my knowledge this list is complete, please let me know if I omitted anything or am wrong.

 Where else can I run?

SVRA Spec Miata has another place to play, at SCRA Vintage Racing events. Over the last few years SVRA has embraced Spec Miata to varying degrees, offering more or less track time, special entry deals, etc. They have rolled up the welcome mat a bit and aren’t giving an exclusive run group as it was for a couple years, but SM’s are allowed to run as a split NA and NB class within “group 3”. Participation seems to vary quite a bit, I found some event results with 7 Spec Miatas and one other class car in the group… and other events with 15 cars and only one Spec Miata. So check your local race results and entry list to see if you’ll have a field to run with. 

SVRA SM follow current SCCA SM rules and can run “current” or “previous”(Toyo?) tires. 

One note is the SVRA racing operates on a STRICT “no-contact” policy, so none of the rubbin-is-racing mentality tolerated in regular SM will fly… That even includes bump-drafting!

Gridlife – GLTC Gridlife Touring Cup – Spec Miatas have traditionally been allowed and welcome, but were always far from competitive with a lack of aero and down about 80 horsepower. As the class continues to develop and go faster the speed differentials are getting to be a bit too much to be reasonable. I wouldn’t count GLTC as a good place to race a SM unless you’re doing a K-swap. 

GCS – Gridlife Club Sport – A “enduro” class specifically designed around attracting the Spec Miatas so outgunned in the GTLC fields (as well as other similar cars). It started last year and hasn’t really gotten off the ground. We’ll see if it gains momentum. 

Enduros: Lemons/Chump/AER/etc – Endurance Racing is a very different type of racing from Sprints. Rather than battling 3 wide into a corner, enduros reward patient, smart, consistent driving with clean pitstops and excessive preparation. Some say it’s a bit like an open track HPDE day, but with trophies. With Spec Miata’s steadfast reliability and low appetite for consumables, they make a very good endurance racing car… if you’re into that sort of thing.  Similar to the other “Catch-all” race classes, beware if buying a Miata built just for or modified to accommodate endurance racing, many would take even more work to be truly SM legal than a ST6/STL/ITA car. Beware of things like a cage built too tall to fit with a standard hardtop.

With Spec Miata’s popularity, there are several regional series based out of specific Track Driver’s clubs like Lime Rock and Monticello. Check local club tracks near you if you’re interested. Here are a couple by me:

Lime Rock Drivers Club Is the exclusive club for Lime Rock Park. While Lime Rock is home to a full schedule of external clubs who race, run schools, and run HPDE events at the track – this series is for members of the actual track club. They run a 5-6 race schedule each year and cars are expected to be run following the current SCCA rulebook. 

Monticello Motor Club  May be one of the most private and exclusive tracks in the country, with very little access outside of members. But behind closed gates they run a pretty popular Spec-Miata adjacent series for their members. There are rumors that the list of tolerated modifications is much more significant than a standard Spec Miata, with visible headers and the faint smell of burning race gas wafting around the paddock… but it works for them and they draw some impressive 15-25 car fields for a full season racing schedule every summer.  

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Hopefully that little bit of info helps you distinguish between the different types of Miatas on track. If you see any omissions, issues, or outdated info, drop a comment and I’ll fix it.