Today in Motorsport History, October 26: Mansell’s Tyre Exploded at 180 mph and Prost Stole the 1986 Title in Adelaide

A McLaren-TAG Porsche MP4/2, the car family Alain Prost drove to the 1986 title, on display at the Porsche Museum in Stuttgart. Photo: Bran / Wikimedia Commons (public domain)Forty years ago today, a tyre on Nigel Mansell’s Williams let go at roughly 180 mph on Adelaide’s Brabham Straight, and a world championship went with it. On October 26, 1986, Mansell needed a third-place finish at the Australian Grand Prix to be champion. Instead he coasted into a run-off area, and Alain Prost, who had picked up a puncture of his own earlier in the race, won the Grand Prix and a second straight drivers’ title for McLaren-TAG Porsche.It remains the cleanest example in Formula 1 of the fastest car having the worst possible afternoon. Williams-Honda won nine of the 16 races in 1986. It arrived in Adelaide with the constructors’ title already banked and left without the one that comes with a name on the trophy.Three Contenders and a Points Sheet That Counted Only 11 ResultsThe finale was a genuine three-way fight. Mansell led on 70 points, Prost had 64 and Mansell’s Williams teammate Nelson Piquet had 63. Mansell needed third or better. Prost and Piquet each needed to win. Only a driver’s best 11 results from 16 rounds counted toward the drivers’ title, which is why the final table read Prost 72, Mansell 70 and Piquet 69 even though Prost had scored 74 in total.Williams had the form to make that arithmetic irrelevant. Mansell had won five races (Belgium, Canada, France, Britain and Portugal) and Piquet four (Brazil, Germany, Hungary and Italy), and the team had clinched the constructors’ title in Portugal. The catch was that two drivers in the same car kept taking points off each other. In Adelaide, Mansell took pole in 1:18.403, Piquet was 0.311 seconds back, and Ayrton Senna’s Lotus-Renault was third.A Race That Kept Changing Its MindMansell gave the lead to Senna at the second corner of lap 1. Piquet passed Senna on that lap and led for six more, until Keke Rosberg, driving his final Grand Prix for McLaren, took over on lap 7 and pulled away. Rosberg had no title to chase and no reason to be polite. Piquet spun on lap 23 without damage but lost several places, and Prost picked up a puncture a few laps later, pitted and dropped to fourth.For a while, Mansell was simply collecting a championship: running near the front, tyres apparently fine, only needing to keep it on the road.The Williams FW11-Honda, the car that won nine of 16 races in 1986 and still lost the drivers’ title. Photo: KevS / Wikimedia Commons (CC BY-SA 3.0)Laps 63 and 64: Two Tyres, One TitleOn lap 63, Rosberg’s right-rear tyre failed and he retired, handing the lead back to Piquet. Prost had just passed Mansell for second, which left Mansell third, still exactly enough. One lap later, on the Brabham Straight at about 290 km/h (180 mph), Mansell’s left-rear tyre exploded as he was lapping Philippe Alliot’s Ligier. He kept the car straight, coasted to a stop in the run-off, and the title went with it.With Piquet leading Prost and Piquet needing a win of his own, Williams called him in for fresh tyres as a precaution against the same failure. Honda’s own account of the race credits Goodyear with warning that his tyres were at risk. The stop dropped him behind Prost, who took the lead. Piquet came back on new rubber but finished 4.205 seconds behind, with Stefan Johansson third, a lap down. Prost had won the race and, with it, the championship.The pit straight of Adelaide’s parkland street circuit during the 2008 Clipsal 500; the track has been reshaped since its Formula 1 years. Photo: Muzzamo / Wikimedia Commons (public domain)Why It Mattered: A Decision Made Under Fear of RubberAdelaide is a textbook case of a team deciding what to protect. Williams had a driver out of the race and another leading it, and chose to stop the leader to avoid a failure it had just seen twice in two laps. That is defensible. It also handed the lead, and the title, to the one rival who needed both. Tyres were already the story of that fortnight: two weeks earlier, Gerhard Berger never stopped for tyres in Mexico while the Goodyear runners behind him blistered and pitted. If you want the mechanics of why one stint ends in a pit stop and another in a puncture, our explainer on tyre degradation and race strategy covers it.The rules played their part too. Prost scored 74 points and was credited with 72 because of the best-11 rule. A points system that discards results turns a title fight into a spreadsheet exercise, and Adelaide is the finale where that spreadsheet had to be consulted twice before anyone could say who had won.A 1986 Williams FW11 alongside its Honda RA166E turbo V6, displayed at the Honda Collection Hall. Photo: Morio / Wikimedia Commons (CC BY-SA 4.0)What Adelaide ChangedFor Prost, it was the second of four world titles, and it made him the first driver to win back-to-back drivers’ championships since Jack Brabham in 1959 and 1960. He would be back in the fight in a very different way three years later, which is a story we covered in Senna and Prost at the 1989 Suzuka chicane.For Williams and Honda, the loss was temporary. Williams-Honda won the constructors’ title again in 1987, and Piquet took the drivers’ crown that year with Mansell second. Honda, the engine supplier that had powered the FW11 with its RA166E turbo V6, became the first Japanese engine supplier to win a constructors’ championship in 1986, a heritage Williams still leans on, as with its recent throwback livery.It was also a day of endings. Rosberg retired from Formula 1 after the race, Alan Jones made his last start, and the Renault turbo engine raced for the last time in F1 before the manufacturer withdrew and then returned as a Williams supplier in 1989. The sport was already legislating the turbo era out of existence: boost was capped at 4.0 bar for 1987 and 2.5 bar for 1988, and engines went naturally aspirated from 1989.Related Reading on Backfire RacingToday in Motorsport History: Berger Never Stopped for Tyres and Gave Benetton Its First Win at the 1986 Mexican Grand PrixToday in Motorsport History, October 22: Senna and Prost at the 1989 Suzuka ChicaneUnderstanding Tyre Degradation and Why It Shapes Race StrategyWilliams’ Madrid Throwback Honors a Title Saudi Money BuiltLead image credit: McLaren-TAG Porsche MP4/2 at the Porsche Museum, Stuttgart. Photo: Bran / Wikimedia Commons (public domain).The post Today in Motorsport History, October 26: Mansell’s Tyre Exploded at 180 mph and Prost Stole the 1986 Title in Adelaide appeared first on Backfire Racing.