Endurance racing is one of the most popular kinds of motorsport, as it arguably offers the ultimate test of a car's durability and a driver's mental and physical fortitude. In the world of endurance racing, there are three races that are considered to be the most challenging; these are the 24 Hours of Le Mans, the 24 Hours of Daytona, and the 12 Hours of Sebring.
The 12 Hours of Sebring, as you can probably guess from the name, is a race held annually at the Sebring International Raceway in Sebring, Florida. Other than the 24 Hours of Daytona, the 12 Hours of Sebring is the biggest and most popular American endurance racing event.
In this article, we'll be taking a look at the 12 Hours of Sebring and share with you everything you might want to know about the history of this event and the cars that you'll see participating in it.
The 12 Hours of Sebring doesn't quite have the legendary status of other endurance races like the 24 Hours of Le Mans, but it's nonetheless a very important motorsports event with a storied history behind it.
The track where the 12 Hours of Sebring is held first opened in 1950, and is partially built upon the grounds of an airfield. The first race on this track was held that same year, on New Year's Eve. The inaugural race was also an endurance event, although this race only lasted 6 hours instead of 12.
The first actual 12 Hours of Sebring wasn't held until just under two years later, on March 15th, 1952. The layout of the track remained unchanged until the 1966 12 Hours of Sebring, which was unfortunately a disastrous year for the event; one driver and four spectators ended up dying in two separate incidents.
This prompted race officials to make numerous changes to the circuit in an effort to make it safer, which included widening the track in some areas and removing or altering certain turns. In addition, modifications were made to the track so that it would be possible for planes to use the airfield while cars were on the track.
The 12 Hours of Sebring is often used by race teams as a means of testing out their cars before taking them to the 24 Hours of Le Mans. Since the race is held in Florida, it's usually pretty hot on race weekend, which is obviously not great for running engines. In addition, much of the track's surface is quite bumpy, which puts a lot of strain on the cars.
As you might be aware, the 12 Hours of Sebring is not like Formula 1 or IndyCar where all of the cars taking part are built to more or less the same standards. Currently, there are five different car classes that compete at this event.
It can be tricky to tell the difference between these classes, though, so let's take a look at each of the classes that participate in the 12 Hours of Sebring and see how they differ.
DPi stands for Daytona Prototype International, and the DPi class is the top class that takes part in the 12 Hours of Sebring. The DPi class replaces the outgoing Daytona Prototype class.
While DPi cars all look fairly similar for the most part, they can vary a lot in terms of the engines they use. DPi cars from various manufacturers can use 4-, 6-, or 8-cylinder engines, and they can be either naturally aspirated or turbocharged. However, all DPi cars are limited to producing about 600 horsepower, and all of them use the same 6-speed sequential gearbox.
In 2022, the DPi class will be replaced by the Le Mans Daytona h (LMDh) class, which will be permitted to race in both the 12 Hours of Sebring and the 24 Hours of Le Mans.
LMP2 is short for Le Mans Prototype 2; as the name suggests, these cars also race at the 24 Hours of Le Mans. LMP2 cars are pretty similar to DPi cars in terms of overall appearance but don't have quite the same level of performance. In addition, the LMP2 class doesn't have as much freedom in terms of what constructors can do.
Every car in the LMP2 class uses the same 4.2-liter V8 that makes about 560 horsepower, compared to the 600 horsepower in DPi cars. However, LMP2 cars are subject to the same restrictions on vehicle weight and tire compounds as DPi cars are.
An LMP2 pitstopping during the 2021 12 hours of Sebring, United Autosports, CC BY-SA 2.0, via Wikimedia Commons
LMP3 cars are basically the junior version of LMP2 cars. Once again, these cars look similar to DPi and LMP2 cars, and have the same restrictions on vehicle weight. However, LMP3 cars have even less powerful engines than LMP2 cars, and are also restricted to using commercially-available tire compounds.
While GTLM cars closely resemble road-going cars, they are still purpose-built racing machines. GTLM cars fit into the broader category of "Grand Touring" racers, and are the top class in this category.
GTLM cars use the same sequential transmissions as other classes, but come with a variety of engines, most of which are tuned versions of the original road-going engines. GTLM cars also have a much greater choice in terms of what tire compounds they're allowed to use.
The GTD class is the entry-level class in the 12 Hours of Sebring. GTD cars also resemble road cars, but are actually real road cars that have been modified for racing.
Also like GTLM cars, GTD cars use many different engines, and they generally weigh about the same as GTLM cars too. It's easy to spot GTD cars at night since they're the only ones that use yellow-tinted headlights.
While the track itself has been updated many times over the decades, Sebring International Raceway has always been the site of the 12 Hours of Sebring. Of all the circuits used in endurance racing around the world, Sebring International Raceway is considered to be one of the toughest.
The track features straights, high-speed turns, and slow but technical turns. The track features very little camber, which makes turning at high speed a lot more challenging. The raceway can be configured for three different tracks; the Full Circuit, the Short Circuit, and the Club Circuit.
The surface of the track is also quite rough and features a few different surface types. Part of the track runs on the original runway of the airfield, which has not been resurfaced. It's not uncommon to see sparks flying out from under the cars as they scrape on the rough, somewhat uneven concrete.
In the early days of the track, one of the biggest hazards drivers faced was simply getting lost on it. The track used to be quite poorly marked, and it was not rare for drivers to leave the track on the runway sections and be unable to find their way back, particularly at night.