The 2005 IRL IndyCar Series began on Sunday, March 6 and ended on Sunday, October 16. The season, which consisted of 17 races, was the 10th season of the IRL IndyCar Series since it split from CART in 1995.
Dan Wheldon was the dominant driver in the series in 2005, winning six races, including the 89th running of the Indianapolis 500, setting the record for most victories in an IRL season. However, the big story of the season was that of Rahal Letterman Racing's Danica Patrick, the fourth woman to compete in the Indy 500 and the first to lead a lap. She would eventually wind up in fourth. Danica's presence was a boost to the IRL's television ratings. The Indy 500's ratings were up 40% from the year before and subsequent races also saw a boost in ratings. Dan Wheldon was also became the first IndyCar driver to won the Indianapolis 500 and IndyCar Series overall driver's title respectively in the same season since Jacques Villeneuve in 1995 PPG IndyCar World Series season and also first ever in the Indy Racing League era.
The season was also the last for Chevrolet in the series, who confirmed in August that they would not return to the IRL (Chevrolet returned in 2012). At the start of the season, only Panther Racing's Tomas Scheckter and Tomáš Enge raced Chevrolet powered cars (although A. J. Foyt IV also started racing for Chevy beginning with the AMBER Alert Portal Indy 300 at Kentucky). The manufacturer situation within the IRL was the hot issue during the second half of the season and continued into the off-season. Toyota announced that they would leave the series shortly after the 2005 season ended, leaving Honda as the only remaining manufacturer in the IRL. Honda extended their engine supply contract through 2009 despite expressly saying that they did not wish to be the IRL's only supplier. The IRL announced that they extended their chassis supply contract with Panoz and Dallara through 2006.
A mandated switch to the single-point re-fueling systems used by some teams in 2004. The IRL only approved one type of fueling probe and buckeye, and these only work as a single-point system. In the approved system, two hoses coming from the storage tank combined at the fueling mechanism handled by the fueler. The crew member previously responsible for the operation of the vent and jack was now free to operate only the jack.
Cars raced on all ovals in the same configuration introduced at the 88th Indianapolis 500 in May 2004 with minimal aerodynamic changes. The changes were limited to specified areas of the underwing and sidepods. The IRL required teams to use the same engine cover as last year without modification.
Defending champion Tony Kanaan finished second in the championship.Teams were allowed to change engines prior to qualifying without penalty at the following events, which were scheduled to be three-day events: Homestead, St. Petersburg, Motegi, Texas, Milwaukee, Infineon, Watkins Glen and California.
The amount of methanol teams may have in their trackside tanks was changed. Teams were allowed to carry 85 gallons for 187.5-mile races, 90 gallons for 200-mile events, 100 gallons for 225-mile events, 125 gallons for 260-mile races, 135 gallons for 300-mile events, 175 gallons for 400-mile events and 225 gallons for 500-mile events.
The mandatory minimum weight of cars was 1,600 pounds, 75 pounds heavier than the oval minimum weight. The additional weight was attributed to the brake system, which consisted of an aluminum brake caliper, steel rotor and pad as specified by the IRL, as well as the limited slip differential in the gearbox.
On March 19, at Phoenix International Raceway, Sam Hornish Jr. won his first race of the season. Bryan Herta sat on the pole. This would be the last time IndyCar would compete at Phoenix until the race was revived in 2016.
On May 29, at the Indianapolis Motor Speedway, Dan Wheldon won his first Indy 500 and his fourth race of the season. However, the focus of the race was on Danica Patrick who led 19 laps, the first time a woman has ever led a lap at Indy. Tony Kanaan sat on the pole.
On June 11, at Texas Motor Speedway, Tomas Scheckter won his first race of the season, sitting on the pole and leading for 119 of 200 laps. This was the last victory for Chevrolet engine in the series before the temporary withdrawal until 2011.
On August 14 at Kentucky Speedway, Scott Sharp won for the first time since 2003 at Twin Ring Motegi, holding off Vítor Meira for the last laps to win. Danica Patrick sat on the pole for the second time in the season after rain washed out qualifying and the starting grid was determined by the fastest times in practice. Tomas Enge returned from injury to finish 11th.
On August 28 at the circuit's inaugural race at Infineon Raceway, Tony Kanaan won the race, taking the lead on lap 52 from points leader Dan Wheldon, who was hampered by fuel problems all day and finished out of the race in 18th. Ryan Briscoe sat on the pole, but caused a three-car accident on lap 20 that also eliminated Hélio Castroneves and Danica Patrick from the race.
On September 11 at Chicagoland Speedway, Dan Wheldon won his sixth race, breaking the all-time record for most wins in an IRL season. Ryan Briscoe originally won the pole but was disqualified for a technical infraction and sent to the back of the grid. The pole winner after this became Danica Patrick for her third (and final) IndyCar pole. Briscoe's weekend got significantly worse as he was involved in a fiery crash with Alex Barron on lap 20. Briscoe was taken by helicopter to a Chicago-area hospital with head and back pain, but was alert. He suffered a concussion, two broken collarbones, a bruised lung and contusions to his arms and legs. The accident resulted in a 16-minute red flag.
On September 25 at Watkins Glen International, Scott Dixon won his first race since his 2003 IndyCar Series Championship season. Hélio Castroneves sat on the pole. This was the first major open-wheel race at Watkins Glen since 1981 and Dixon's first road course victory. As of 2024, this was the final IndyCar Series victory for Toyota engine to date.
On October 16 at California Speedway, Dario Franchitti won his second race of the year over Tony Kanaan by 0.111 s. Chevrolet powered cars finished 7th and 8th in their final IRL race while Toyota powered cars had a best finish of 5th in theirs. IndyCar would not return to this track until 2012.
Any driver who qualifies but does not start (DNS), earns all the points had they taken part.
RY Rookie of the Year
R Rookie
Ties in points broken by number of wins, followed by number of 2nds, 3rds, etc., and then by number of pole positions, followed by number of times qualified 2nd, etc.
Dan Wheldon
Honda
Danica Patrick