Enlarge / A field of GT cars at the start of the 2021 12 Hours of Sebring. If you needed proof that sports car racing is too much for the casual fan, consider the fact that the #79 white Porsche 911 RSR is in fact radically different from the #16 blue Porsche 911 GT3 R next door. From next year, this confusion will be reduced.


On Saturday, the North American sports car season will wrap up with the Petit Le Mans, a 10-hour race that will be held at Road Atlanta in Georgia. This year’s Petit Le Mans is also the final race for a fan-favorite car class known as GTLM. The category covered Le Mans-homologated versions of two-door production cars, which over the years have been a playground for manufacturer-backed programs and some of the world’s best racing drivers.

On the one hand, the removal of GTLM is an important step for the American side of endurance racing, as it ends a direct link between the WeatherTech SportsCar Championship and the annual 24 Hours of Le Mans. But this decision also makes the sport a little less complicated.

“Even some of the car enthusiasts find it hard to understand why the red BMW is so much faster than the yellow and blue or [why] the red, white and blue Porsche is so much faster than the #9 car or the #16 or the #88,” said John Doonan, president of the International Motor Sports Association (IMSA), the organizer of the sport.

Next year IMSA will still have a place for factory teams, but it is moving to cheaper, more user-friendly cars with the introduction of a new class, called “GTD-Pro”. Let’s take a look at what’s going on.

Acura has chosen the GT3 category for its NSX race car.  This year, Magnus Racing entered an NSX GT3 at Petit Le Mans.
Enlarge / Acura has chosen the GT3 category for its NSX race car. This year, Magnus Racing entered an NSX GT3 at Petit Le Mans.

Jake Galstad

The WeatherTech series has its roots in the first Petit Le Mans, which took place in 1998. This race adopted the same technical rules used by the Automobile Club de l’Ouest, the organization that organizes the annual 24-hour race. from the Mans. , France. Among these rules were categories for road car versions modified for racing. This is where things get tricky, so bear with me.

Originally there were two GT classes, called GT1 and GT2. GT1 cars were more modified, more powerful and more expensive to run. They also generated more downforce. Eventually, the category became too expensive and disappeared. GT2 stayed and was renamed GTE at Le Mans and GTLM in IMSA competition (because having a GT2 class but no GT1 class made too little sense, even for an unnecessarily complicated sport like endurance racing).

For the past few years, the same problem that killed GT1 has come to GTLM/GTE. Cars have become more and more specialized; for example, Porsche went to the trouble of making a mid-engined 911 race car. And that has made vehicles more expensive to campaign on, especially for the privateer teams that are the lifeblood of the sport.

Instead, these privateers largely shifted to another class of production sports car called GT3. This category was created specifically for enthusiasts, even going so far as to mandate driver aids like anti-lock brakes. Performance differences between different car brands were adjusted to maintain a relatively level playing field (called “balance of performance” or BoP), and the result was full grids at races around the world.


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