This story was originally published in 2011—Ed.
From the start, it was envisioned as part sporting event, part skunkworks: Indianapolis millionaire Carl Fisher sought to build a proving ground for new cars and ideas, where automotive reliability, speed and strength would be tested. A century later, the Indianapolis 500 has been true to Fisher's dream, and your everyday ride—from the drivetrain to the road and rubber on which it rolls—owes much to the race.
"It's made American cars perform a lot better," says Indy legend A.J. Foyt. "We put it way over the line at Indianapolis, so if it works there, it'll work on the highway."
"At Indy, we are the NASA of the production-car world, and that's clearly why manufacturers are involved—it's such a good testbed," says Mario Andretti, the 1969 winner.
Famed Indy driver and car builder Dan Gurney offers a different analogy. "Racing is like warfare," he says. "It accelerates the evolution of ideas."
Here's a look at some of the advances sparked by the battle in the Brickyard.
1. Rearview Mirror
Driver Ray Harroun stirred controversy at 1911's inaugural 500 by entering the only single-seater in the field, a stinger-tailed Marmon Wasp. His fellow drivers, each of whom had a "mechanician" riding shotgun, knew that by motoring solo, Harroun would have an edge in weight and aerodynamics. They complained that without a spotter beside him, Harroun would be blind to racers closing in from behind and thus be a danger to all. His solution: a rectangular mirror mounted to the cowl on four steel dowels. Harroun won the race, and by the mid-teens the device—marketed as a "mirrorscope" or "cop-spotter"—was a popular aftermarket accessory. Incidentally, Harroun's mirror was a bust: It vibrated so fiercely during the race that he couldn't see a thing in it.
2. Tire Tech
Early racers rode on tires of rubber and fabric, usually heavy cotton. If that sounds like a delicate arrangement, well, it was: The fabric made for weak sidewalls and also generated a lot of internal friction and thus heat; tire pressures could double in a couple of laps, and one turn too many could bring on a blowout.
That changed in the mid-teens, when tires with cords of twisted thread, not woven fabric, debuted at Indy. Formed by crisscrossing plies and sandwiched with rubber, the cords made for a looser but stronger weave and ran far cooler.
In 1925, Firestone introduced the balloon tire at Indy. It offered a wider tread for better traction, as well as lower inflation pressure (30 psi versus the 50 psi common at the time), which smoothed the speedway's bumps, improving stability and handling. Indy lap times dropped, and "softer" tires quickly made their way into the consumer auto market.
"Racing had always been the test laboratory, because the demands of the track were far more extreme than anything on the street," says Al Speyer, executive director of Firestone Racing. "Indy was always the cornerstone."
The wide, low-profile tires found on many sports cars today originated at Indy in the 1960s, when Goodyear and Firestone had mobile labs at the race. Average lap speeds rose by 15 to 20 mph that decade, so tiremakers sought a new product with greater lateral muscle in the turns. That yielded shorter, stronger sidewalls and a wider footprint, attributes also adopted in consumer tires. Even now, Indy tire research influences rubber on the road as companies seek tread compounds that boost traction, resist wear and fight the heat buildup that Speyer calls "the enemy."
3. Magnesium Wheels
Racer and engineer Ted Halibrand spent World War II working with Douglas Aircraft. When the shooting stopped, he put his expertise to use in auto racing, crafting the first of what would become his trademark magnesium-alloy wheels. The 500's winner rode on Halibrands in 1946 and every year thereafter through 1963. Usually alloyed with aluminum and zinc, the wheels eventually made the jump to hot rods and muscle cars—and into motorhead vernacular as "mags." The low-profile rims found on many sports cars today can be traced to the original Halibrands.
4. Lightweight Engine Parts
Having quit his namesake car firm, Louis Chevrolet founded the Frontenac Motor Co., which never offered a viable production car, but developed a string of wildly successful Indy racers with "Fronty" aluminum crankcases and other hardware. A ground-up Frontenac design won the 1921 race, and in 1923, driver L.L. Corum finished fifth in a Model T—a Model T!—equipped with a lightweight Fronty cylinder head. Chevrolet and engineer C.W. Van Ranst also used a lot of aluminum in engines Frontenac built for commercial clients such as Stutz. By the mid-'30s, hot rodders were routinely modding their engines with aluminum parts. Indy thus hosted early efforts to increase speed by trimming vehicle weight, and helped invent the high-performance auto aftermarket.
5. Superchargers and Turbochargers
Supercharger technology predates the automobile by more than a generation (it evolved from blowers used to stoke blast furnaces), but it didn't catch on with auto enthusiasts until Mercedes sent a team of supercharged cars to Indy in 1923. The German cars were also-rans, but the underlying idea—that pumping air into an engine's intake manifold boosts power—inspired Fred Duesenberg to develop a centrifugal supercharger for the 1924 race. A blown Duesey won that year, and the devices moved quickly into the mainstream. By the time superchargers were offered on the iconic Cord 812, in 1937, Indy race teams had honed the devices considerably.
Meanwhile, a variation on the technology was found in ships, airplanes and locomotives: turbochargers that pumped air into the combustion chamber like superchargers but were powered by exhaust gases, not the crankshaft. The technology debuted at Indy in the Cummins Diesel Special of 1952, a crazy-fast car that was both made and undone by its turbo: The low-hanging air intake sucked up tire debris and clogged during the race, causing the engine to overheat. Later race teams "improved them a lot," legendary car builder A.J. Watson says. Detroit pursued turbos with surprising speed, offering the first production turbocharged gas engines in the 1962 Olds Cutlass Jetfire and Chevy Corvair Monza Spyder.
By the mid-'20s, race engineers recognized that superchargers were vexed by an unwanted byproduct, one that they would share with turbos: Air warmed as it was compressed and shoved into the intake manifold, and in the process lost density—thus compromising the very point of having a blower. The solution was a heat exchanger bolted between the charger and the engine. The first, in 1926 or 1927, was reputedly the brainchild of Frank Lockhart, an engineer and driver in Harry Miller's shop. The idea didn't take to the street until the '70s, when Porsche's early Turbo Carreras were augmented by intercoolers. Today, they're commonly found on supercharged and turbocharged passenger cars.
7. Front-Wheel Drive
After winning at Indy in 1922, driver Jimmy Murphy placed an order for a front-wheel-drive car, figuring he'd post better times if he were pulled, rather than pushed, through the turns. Legendary engineer Harry Miller, whose cars and engines won the 500 a dozen times, responded with a design that enjoyed success at Indy for years. A transverse-mounted transmission eliminated a driveshaft and heavy rear differential, lopping as much as 150 pounds from the car's weight. It also enabled the driver to sit on the floor pan, lowering the center of gravity. Murphy died in a wreck in 1924, before driving the car, but Dave Lewis piloted the Miller to second place at Indy in 1925, prompting other teams and automakers to adopt the configuration. In 1929, two American passenger cars—the St. Louis–built Ruxton and the Cord L-29—went into limited production with front-wheel drive. In the 80-odd years since, it has come to dominate the world's passenger cars.
8. Alternative Fuels
Indy teams studied alternatives to gasoline long before any inkling of an energy crisis. Driver Leon Duray experimented with methanol in Indy racers in or about 1927, midway through a career that saw him win the 500 pole twice and start six of his eight races in the top five. A methanol-fueled Miller set the longest-standing (for nine years) Indy lap record of 124.02 mph in 1928. In 1965, a year after gasoline increased the severity of a fiery seven-car Indy crash, the racers switched—permanently—to less volatile alcohol fuels.
9. Elevated Curves
In 1911, when most roads were built for horse traffic, Indy became perhaps the first American motorway with banked curves. Averaging 9 degrees, 12 minutes, they helped early racers achieve high speeds—and may have encouraged highway engineers. When a panel of them designed the Lincoln Highway's "Ideal Section" in the early 1920s, it decreed that curves be likewise banked and have a minimum radius of 1000 feet—safe for cars going 35 mph. As Indycars became faster in the 1930s, a string of deadly wrecks led officials to widen the Brickyard's curves and redesign their retaining walls to return errant cars to the track. In 1955, similar thinking spawned a standard of the modern American highway: the Jersey barrier.
Many early fatalities occurred when drivers were ejected from vehicles, but it wasn't until 1922 that Barney Oldfield ordered a harness for his Indycar from a parachute manufacturer—and reputedly became the first driver to buy seatbelts. (Oldfield, also the first to achieve a mile a minute on an oval track, and inspiration for the traffic-cop inquiry—"Who do you think you are, Barney Oldfield?"—had evidently grown cautious; he didn't race at Indy in 1922 but rather drove the pace car.) Automakers caught the safety bug much later. Nash offered factory-installed seatbelts in 1949, and the Big Four made front-seat belts standard in 1964.
11. Four-Wheel Disc Brakes
Another gift from racing genius Harry Miller, four-wheel disc brakes first appeared on his four-wheel-drive Miller Specials of the late '30s. The midengine cars weren't very fast, but they sure could stop. Discs caught on among other teams in the late '40s. They were first offered to American motorists on Crosley's tiny passenger cars of 1949. "The race created the disc brake, 100 percent," says Mario Andretti, who ran the 500 29 times and won it in 1969
12. High-Performance Diesels
Diesels were known for brute strength, long life and black smoke, but hardly for speed, when Clessie L. Cummins convinced speedway officials to let him enter the race with an experimental car in 1931. Dropped into a custom Duesenberg chassis, the four-cylinder Cummins didn't break any records, but it ran the entire race without a pitstop and took 13th—and did it five years before Mercedes marketed the first diesel passenger car. Cummins steadily improved his diesels and had a breakthrough for the 1952 race, when he commissioned car builder Frank Kurtis to craft a low, sleek chassis around a 6.6-liter turbocharged truck motor laid on its side. Driver Freddie Agabashian shocked the racing world by riding the Cummins Diesel Special to the pole. Mercedes and Peugeot began offering the first turbodiesels to the masses in 1978.
13. Hard Driving Surfaces
Indy offered an early and painful demonstration of the fact that roads built for horses would not meet the demands of fast-spinning rubber tires. The track's original surface was a variation on bituminous macadam: gray gravel laid atop a clay base and covered in a thick slathering of pitch, which itself was layered under 2 inches of finer gravel and pitch and then covered with white stone. The track's designer promised that once smoothed by steamroller, this concoction would be hardier, safer and faster than other American courses. But the surface came undone in the opening minutes of the speedway's August 1909 inaugural weekend. As Charles Leerhsen writes in his entertaining book, Blood and Smoke: A True Tale of Mystery, Mayhem and the Birth of the Indy 500 (Simon & Schuster, 2011), track debris "could rip a man's face to bloody ribbons, crack or work its way around the edges of his goggles, and invade his eyes, blinding him to slow-moving or broken-down vehicles ahead." Deep ruts led to rollovers. Five people died: a driver, two riding mechanics and two spectators. In the fall of 1909, Fisher and his partners rebuilt the Indy track with 3.2 million bricks. The Brickyard was born. That same year, 92 percent of America's 2.2 million miles of public roads were dirt; concrete pavement accounted for 9 miles. Today, our paved roads span 2.7 million miles; the interstate system alone required nearly 300 million cubic yards of concrete.
14. Four-Wheel Drive
This now-common consumer-car setup saw an early application at the speedway. In 1934, a 4WD Harry Miller car led the race for several laps. In the late '30s, Miller designed another line of 4WD racers, the Gulf Specials, which attracted a lot of ink but proved no more sure-footed than racers with two-wheel drives—and slower than many of them. That didn't stop others from championing the form: In 1946, a twin-engine Fageol managed plenty of speed before it ran into a wall, and in 1963, Andy Granatelli entered an all-wheel-drive car with Bobby Unser at the wheel, to middling effect.
Indy cars have been platforms for streamlining theory since the first race: Ray Harroun's 1911 Marmon Wasp was so named because its tail tapered to a point, an early (and farsighted) stab at trimming drag.
In the early '70s, when most American cars were aerodynamic battering rams, Indy teams borrowed from aviation to boost speeds and trim fuel consumption, deploying inverted wings and ground-effects skirts on race cars. The whale's tails and spoilers in vogue among modern tuners can trace their lineage to Indy teams' efforts to increase downforce and cheat the breeze.
In 1971, driving legend and team owner Dan Gurney added a thin bracket of sheet metal to the trailing edge of his Indy car's rear wing—and was shocked to find that it dramatically boosted the car's traction and speed in the turns.
Today, a variation on the Gurney flap can be found on a slew of modern passenger cars from BMWs to Toyotas: It's the little lip at the trailing edge of the trunklid. Never mind that rear-end downforce isn't critical on either a luxury ride or a front-drive econobox. "Whether it's there as a styling item or it really works," Gurney says, "well, that's the way the industry goes."
With a suite of aerodynamic features, the Chaparral 2K debuted in 1979 and won six times in 27 Indy series starts in just three seasons. Johnny Rutherford drove a 2K to victory in the 1980 Indy 500.