We’re chronicling 100 days of Indy 500 history on #SpeedRead leading up to the historic 100th Running. With 95 days to go, IMS Historian Donald Davidson explains how 33 cars became the standard at Indy.
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After 40 cars met the qualification requirements to start in the 1911 “500,” the Contest Board of the American Automobile Association (AAA) decided, following the race, that this was too many for a two-and-a-half-mile track. A formula was devised to establish a “safer” number, and the conclusion was that each car, spread equally around the track, should be entitled to 400 feet of racetrack. Since 400 feet “goes into” two-and-a-half-miles 33 times, 33 became the magic number.
In the meantime, Indianapolis Motor Speedway President Carl G. Fisher had decided that the 1912 “500” should be restricted to 30 starters rather than 33. This became academic when only 24 qualified that year, followed by 27 in 1913, but because there were 45 entries in 1914, and several cars posted speeds too slow to be included among the 30, Fisher announced that the 1915 field would be expanded to 33. As luck would have it, only 24 met the requirements that year, and it was not until 1919 that there was a full field of 33 cars.
There were several further years with short fields, but with a drastic change to the technical specifications for 1930, the maximum for that year, plus 1931 and 1932 was expanded to 40 cars, although only 38 met the requirements in 1930. Because the cars were now lined up three-abreast, it meant that 40 would constitute 13 rows of three, followed by a single car in the last row. It was decided for 1933 to fill out the 14th row, thus resulting in a record 42 starters. For 1934, the number was returned to 33 and it has been that way ever since with the exception of 1947, when only 30 cars took the green; and 1979 and 1997, when due to extenuating circumstances 35 cars were permitted to start.