How Endurance Racing Works

Endurance racing stands out from other kinds of motorsport in that it tests not only the stamina and skill of the driver, but the sustained durability and reliability of the vehicle. Whether it's for 24 hours at Le Mans, 12 hours at Sebring, 10 hours at Petit Le Mans or 1,000 kilometers (621 miles) in the European races, these events prove not only which driving team reins supreme, but also which car can go the distance.

It's no wonder that auto manufactures take such pride in boasting about their wins at the great endurance races. However, auto manufacturers do not hold a monopoly on endurance racing vehicles -- far from it. Independent groups, known in the racing world as "privateers," also field fleet fleets on the circuit.

Endurance races usually take place on closed tracks with closed wheel cars (unlike formula cars, which have open wheels -- that is, wheels outside of the car body). The typical event involves teams of two to four drivers attempting to cover a set distance the fastest or to go the farthest in a specified time. Over the course of the race, the drivers must make pit stops to fuel and service the car, as well as to switch drivers, who each drive a "stint" lasting around an hour to 90 minutes. Because of the tactical importance of these switches, stints can be highly variable in length. Some races limit the stint length for safety reasons.

Several classes of car compete for endurance prizes. Some classes are populated by prototypes built to specifications set out for that race. The Le Mans Series (LMS) and American Le Mans series (ALMS) alone use two classes of prototype closed-wheel car. The first class, called Le Mans Prototype 1 (LMP1), is famously manufactured by Audi, Peugeot and Aston Martin. LMP2 cars are smaller, lighter and less powerful, but have potentially better power-to-weight ratios. Porsche, Acura and Mazda are known for their LMP2 prototypes.

In addition, three classes of sports cars, including Corvettes, Vipers, Saleens, Aston Martins, Porsches, Ferraris and BMW GTs, also compete at LMS and ALMS events. Races can also be limited to "spec cars" (in which all racers drive the same make of car, with the same chassis and engine) or touring cars (vehicles based not high-performance sports cars, but rather road cars).

Even in races that run such great distances and last so long, drivers and vehicles often achieve victory by a narrow margin. Many a 24-hour race has come down in the end to which team made the fewest mistakes.

Now that we have the basics down, let's take a trip around the circuit.

Le Mans Grand Prix d'Endurance, also known as the Le Mans 24-Hour Race, remains the most prestigious of all endurance races. It has been held almost every year since 1923 at the 8.5-mile (13.7-kilometer) Sarthe road-racing circuit near Le Mans, France. Multiple classes of vehicle compete side-by-side, with prizes going to both the overall winner and the winner of each class.

Le Mans is the first jewel in endurance racing's Triple Crown, as the three most historically challenging endurance races are known. The 24 Hours of Daytona, held at Daytona International Speedway in Daytona Beach, Fla., and the 12 Hours of Sebring, held at Sebring International Raceway, a former Army Air Force base in Sebring, Fla., round out the Triple Crown.

The 24 Hours of Daytona has changed its name as it has gone through various sponsors (it's currently called the Rolex 24 at Daytona), but the race has remained much the same. Drivers pit touring cars and Daytona prototypes against one another on a 3.5-mile (5.6-kilometer) combined road course. Part of the race takes place on the NASCAR track, and part occurs on a winding infield road course. Daytona's tri-oval track has a shape between an oval and a triangle, and has consequently sharper turns than a squared oval or true oval track.

Run on one of the oldest continuously operating racetracks in the United States, the 12 Hours of Sebring race consist of a 3.7-mile (6-kilometer), 17-turn road course featuring long straight-aways, blistering high-speed turns and challenging slow corners. Race fans know the Sebring track for its rough and bumpy surface, parts of which run along old sections of World War II-era landing fields. These difficult conditions, combined with the heat of south central Florida, make Sebring a truly demanding course for both car and driver.

The popularity of endurance motorsport has given rise to several racing series, usually inspired or anchored by a major championship race. Prominent examples include the Rolex Sports Car Series of 12 races, which begins with the 24 Hours of Daytona, the American Le Mans Series (ALMS) and the Le Mans Series (LMS).

You might imagine that all of the engineering that goes into making reliable, fuel-efficient endurance racers could be put to good use in consumer cars. As we'll see in the next section, you're right on the money.

Drivers in endurance races must vary the way they drive to balance fuel consumption and performance, and must even adjust for weight distribution and balance shifts throughout the race. Because of the heavy demands on track, car, driver and crew, endurance racing has given rise to some of the most significant technical advancements in motorsport.

Endurance motorsport evolved as a different kind of challenge than Grand Prix. Instead of building cars that could blow the doors off the competition for a drag, sprint or short race, engineers faced the test of building vehicles that were both sporty and reliable -- not to mention as fuel-efficient as possible, to cut down on the number of pit stops.

Thus, endurance racing helped drive research into fuel efficiency, reliability and aerodynamics. All race cars require reliability and stability, of course, but these factors became especially important in off-track endurance racing, where roads were not maintained for racing conditions and a car could really take a beating over the course of a day.

Tires, too, have always been a major concern in endurance racing. The effects on acceleration, braking and handling of tires heating up and wearing down can be substantial, and the frequency with which tires need to be changed, along with the speed with which the pit crew can change them, can make a huge difference in the outcome of a race. One driver said that switching the tires on his car to a different brand saved his team 4 seconds per lap in a factory Corvette at Sebring.

Tires that can last more than one stint with a single driver provide a major advantage to the team that equips them. However, this requires tires that can still provide grip to the road even when worn down and somewhat cool, when their coefficient of friction is at its minimum.

Solving problems like these at endurance races provides tire manufacturers a useful focus for research, even while the races provide a proving ground for testing their tires for performance, longevity and consistency. Consider, too, the positive publicity that might come from having their company's product on the car that wins Le Mans, Daytona or Sebring. Michelin must agree -- in 2009, it supplied tires for 41 of the 55 cars entered in Le Mans.

So, next time you look at a mileage sticker or buy a set of 70,000-mile (112,654-kilometer) tires, spare a thought for endurance racing. Whether you think of it as a great big proving ground, or revel in the excitement of pushing the limits of machine and driver, it's something to get revved up about.

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