15 Ways the Indy 500 Changed How You Drive

Though it's one of the biggest races in the world, the Indianapolis 500 has always been as much skunkworks as sporting event. As the great race celebrates its centennial, we look back on the automotive innovations that started at Indy and found their way into your car.

By Earl Swift
Ray Harroun, who won the first Indy 500, mounted a rearview mirror on his car's cowl. He reportedly got the idea from one he saw on a horse-drawn vehicle.


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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.

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