The 1986 Australian Grand Prix was a Formula One motor race held on 26 October 1986 at the Adelaide Street Circuit, Adelaide, Australia. It was the last of 16 races in the 1986 Formula One season, and decided a three-way tussle for the Drivers' Championship. The drivers in contention for the title were; Nigel Mansell, Nelson Piquet, both of whom were racing for the Williams-Honda team, and McLaren's Alain Prost.
Mansell took pole position for the race, but a poor start off the grid enabled team-mate Piquet, Ayrton Senna and Keke Rosberg to overtake him and demote him to fourth by the end of the first lap.
A few laps into the race, Finland's Keke Rosberg, in his final Grand Prix, took the lead from Piquet. However, the Finn retired with a puncture on lap 63, handing the lead back to Piquet and elevating Mansell into third place, which would have been sufficient for the Englishman to secure the championship. One lap later, Mansell's race ended as his left-rear tyre exploded on the main straight with 19 laps remaining. The title was then between Piquet and Prost with the Frenchman needing to finish ahead of the Brazilian to successfully defend his title. Following the tyre failures of Rosberg and Mansell, the Williams team called Piquet in for a precautionary tyre change leaving him 15 seconds behind. He made a late charge to close the gap to 4.2 seconds but Prost took victory to win his second of four titles.
It was not until the 2007 Brazilian Grand Prix that there were again three possible drivers' title contenders entering the final race of the season.
Coming into the race, three drivers had a chance of winning the title. British driver Nigel Mansell was the leader; six points behind was defending champion Alain Prost, and one point behind Prost was Mansell's teammate at Williams, Nelson Piquet. In fourth was Ayrton Senna, who was guaranteed to finish in that position regardless of what happened. Prost was aiming to become the first driver since Jack Brabham in 1959 and 1960 to win back-to-back World Drivers' Championships.
The Williams cars of Mansell and Piquet were far superior in speed to Prost's McLaren. However, Prost's consistency had seen him accumulate points all year, while the Williams pair battled with one another and their mind games eroded what would have been a dominant season for the team.
To win the championship Mansell needed either third position or higher, or for both Prost and Piquet to finish in second place or lower. For Prost or Piquet to win the championship, they would have to win the race, and see Mansell finish in fourth position or lower.
Unlike the Drivers' Championship, the Constructors' Championship had already been decided in Williams' favour, as they had a 48-point advantage over McLaren. McLaren's place as runners-up was secured, as they were 30 points ahead of third placed Lotus.
Mansell took pole position for the race with a time of 1 minute 18.403 seconds. His teammate, Nelson Piquet, and Lotus' Ayrton Senna were the only drivers within a second of Mansell's time. The third title contender, Alain Prost, was on the second row of the grid in fourth.
The prospect of a three way battle for the Drivers' Championship crown attracted a capacity crowd of 150,000 to the tight, but fast Adelaide circuit.
Mansell started from pole position but yielded the lead to Ayrton Senna's Lotus at the second corner on lap 1 and fell behind both Piquet and Keke Rosberg on the same lap. Piquet also overtook Senna on lap 1 to take the lead but it would last only six laps as on lap 7, Rosberg took the lead from Piquet and began to build a sizeable gap between himself and the rest of the field.
On lap 23 Piquet spun, although no damage was sustained to the car, and he continued the race despite dropping back several places. Prost suffered a puncture a few laps later and he dropped to fourth position after having to pit. Piquet charged back through the field, passing Mansell for second place on lap 44, but Prost closed on the two Williams cars and, with 25 laps to go, all three championship contenders were running together in positions 2, 3 and 4.
The battle became one for the lead on lap 63 when Rosberg suffered a right rear tyre failure and retired from the race. Rosberg later revealed that he would never have won the race anyway unless Prost failed to finish or had sufficient problem not to be able to challenge, as he had promised Prost and the team that he would give best to his team mate to help his bid to win back-to-back championships. Prost had just passed Mansell for third which became second when Rosberg retired, with Piquet now leading. Mansell only needed a third-place finish to win the championship.
Mansell was still in third position when, on lap 64, his left rear tyre exploded at 180 mph (290 km/h) on the high-speed Brabham Straight while lapping the Ligier of Philippe Alliot, sending a shower of sparks flying behind him and severely damaging his left rear suspension. The Williams coasted to a stop in the run-off area at the end of the straight, Mansell managing to avoid hitting anything. Fearing the same happening to the second car, Williams called Piquet to the pits and Prost took the lead. Piquet would make a late charge, closing the gap from 15.484 seconds with 2 laps remaining to just 4.205 at the finish and Prost claimed both the race and the World Championship. Prost had so little fuel left that he pulled up only metres past the finish line.
In his last race for Ferrari, Stefan Johansson completed the podium in third place, albeit a lap down on Prost and Piquet. Martin Brundle ran out of fuel as he crossed the line in fourth place in his Tyrrell-Renault. His team mate Philippe Streiff finished fifth 2 laps down, while Johnny Dumfries finished sixth in his Lotus-Renault.
By winning, Alain Prost became the first and so far only driver to ever win the Australian Grand Prix in both non-championship and World Championship form, having won the non-championship 1982 Australian Grand Prix run for Formula Pacific cars at the Calder Park Raceway in Melbourne.
This was the last race for the Renault turbo engine, the French company being the pioneers in F1 turbocharging back in 1977, as well as Renault's last Formula One race as an engine supplier until their return with Williams at the 1989 Brazilian Grand Prix. It was also the last Formula One race for Australia's 1980 World Champion Alan Jones and his team mate Patrick Tambay, and the last race for Team Haas, whom both Jones and Tambay drove for. It was also the last race for Lotus driver Johnny Dumfries, Osella's Allen Berg, Zakspeed's Huub Rothengatter, and 1982 World Champion Keke Rosberg.
Nelson Piquet 8 (1–6, 63–64), Keke Rosberg 56 (7–62), Alain Prost 18 (65–82)Bold text indicates the World Champions.
Note: Only the top five positions are included for both sets of standings.