page_title: Indianapolis 500
section_title: Technical regulations
hierarchical_section_title: Indianapolis 500 / Technical regulations
context_page_description: The Indianapolis 500, also formally known as the Indianapolis 500-Mile Race, or simply the Indy 500, is an annual automobile race held at Indianapolis Motor Speedway in Speedway, Indiana, United States, an enclave suburb of Indianapolis. The event is traditionally held over Memorial Day weekend, usually the last weekend of May. However, due to the COVID-19 pandemic in 2020, it was delayed to be held on August 23.
  It is contested as part of the IndyCar Series, the top level of American Championship Car racing, an open-wheel, open-cockpit formula colloquially known as "Indy Car Racing". The track itself is nicknamed the "Brickyard", as the racing surface was paved in brick in the fall of 1909, with a yard of brick remaining exposed at the start/finish line.
  The event billed as The Greatest Spectacle in Racing is considered part of the Triple Crown of Motorsport, which comprises three of the most prestigious motorsports events in the world, also including the Monaco Grand Prix and the 24 Hours of Le Mans.
context_section_description: Technical specifications for the Indianapolis 500 are currently written by IndyCar. Rules are generally the same as every other IndyCar race. In the past, particularly during the era in which USAC sanctioned the Indy 500 (but CART sanctioned the other Indy car races), rules at Indy slightly differed at times. The result, for example, would be a particular chassis or engine configuration being legal at Indy, but not so at the CART-sanctioned events. This was rather commonplace in the 1980s and early 1990s, when "stock-block" engines (namely the V-6 Buick) was allotted an increased level of turbocharger boost by USAC at Indy, compared to the purpose-built V-8 quad-cam engines. While the "stock block" engines were technically legal in CART competition, they were not given the increased boost advantage, which effectively rendered them uncompetitive, and precluded their use by teams. The most famous manifestation of the USAC rules disparity was the Ilmor-built Mercedes-Benz 500I engine fielded by Roger Penske in 1994.
  Teams may enter up to two machines under a given car number—the "primary" car and a "backup" car. The backup car is identified by the letter "T". For example, the two cars for the #2 team would be numbered #2 and #2T. Both cars may be practiced during the month, but due to engine lease rules, they must share the same engine. It is not uncommon for teams to prefer their backup car, if it is deemed faster, or for other strategic reasons. Additionally, as the month wears on, a "T car" may be split off into a separate entry, and reassigned a new number, or be sold to another team.
  All cars must pass a rigorous technical inspection before receiving a sticker signifying that the car is eligible to practice. Various criteria include minimum weight, dimensions, and approved parts, particularly safety equipment. Before and after qualification attempts, cars must pass another inspection. The pre-qualifying inspection is focused on safety aspects and is done on the pit lane qualifying queue. It is relatively brief, due to the time constraints of the qualifying procedure. The post-qualifying inspection is much more stringent and lengthy, taking place in the garage area. It is to detect deviations from the performance guidelines set forth by the league, and cars can and have been fined or outright disqualified if they fail inspection.
  During the race, work on the car is permitted, but it is usually limited to routine pit stop work (changing tires and refueling) and minor adjustments (wing angles, etc.) Pit stop activity is rigorously rehearsed by the crews and in modern times, routine pits stops are regularly completed in under ten seconds. Other more involved work, such as replacing damaged bodywork (wings, nose cones, etc.), can also be completed quickly by the crews. More lengthy repairs are allowed, and since 1998 teams are permitted to return to the garage area to make repairs. However, there are limitations to the extent of repair work allowed and the practicality of such work. Teams are not allowed to change engines, and since 1933 a rule has been in place where teams are not allowed to add oil. In addition, the officials designate a certain lap after which cars off the track being serviced/repaired are no longer permitted to return to the race.
caption: Penske PC-23 Mercedes, 1994 winning car
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