How Hamilton sealed his third title at the rain-hit 2015 United States Grand Prix

Lewis Hamilton won the 2015 United States Grand Prix in Austin, a race held at the Circuit of the Americas over fifty-six laps, and clinched his third world championship in the process. The race was run through a soaked weekend, with a practice session cancelled and qualifying pushed back to race morning, and only twelve cars reached the finish.

What was at stake going into Austin?

This was the thirty-seventh United States Grand Prix as a world championship round and the fourth held at this circuit. Hamilton was the defending race winner and led the drivers' table with a 66-point advantage over Sebastian Vettel of Ferrari. His Mercedes teammate Nico Rosberg was a further seven points back.

Mercedes had already secured the constructors' title at the Russian Grand Prix. The constructors' championship is awarded to the team, using points from both of its cars. Ferrari held second on 359 points, 139 ahead of Williams, and Hamilton's 302 points kept him 66 ahead of Vettel and 73 ahead of Rosberg.

Rossi became the first American to race at the Circuit of the Americas, taking over the Manor Marussia seat that Roberto Merhi had held in Russia. Sauber marked its 400th Grand Prix in Austin.

Hamilton won the wet Austin race and his third world championship, with Rosberg's late slide handing him the lead for good.

Why was the weekend so wet?

Forecasts warned of wet conditions across the weekend, with the worst expected on Friday afternoon and Saturday. Race day, by contrast, was forecast to be a little drier, though still damp.

Practice was cut back. The second session was cancelled because of heavy rain and a thunderstorm, and the sessions that did run were on wet or changing tracks. Saturday's running took place without spectators for their safety, and qualifying was pushed back to the morning of the race.

How did the cars change for Austin?

Alonso ran a new power unit, which he had already used once in practice in Russia and which cost him a grid penalty. A power unit is the engine together with its energy recovery system. Mercedes added two ears to the top of its airbox to cool the energy recovery system ahead of the high altitude in Mexico.

Vettel and Raikkonen both needed new power units. Having used the four allowed for the season, each took a ten-place grid penalty. Manor's Will Stevens was sent back 20 places for an engine, turbocharger and MGU-H change, and Renault used eleven of its twelve remaining tokens on its power unit. A token is the allowance that lets a team make a power unit change, so each one spent reduces what is left for the rest of the season.

Red Bull and Toro Rosso turned down the Renault update because the grid penalties were not worth it. Red Bull and McLaren introduced new front wings, copying a Mercedes idea that pushes the air out towards the edges of the front tyres, and Ferrari made similar changes to its SF15-T.

Two DRS zones were in use again, one between turns eleven and twelve and one on the main straight between turns twenty and one. DRS is a flap that opens on those straights for a car within a second of the one ahead. Pirelli supplied the white-banded medium as the prime tyre and the yellow-banded soft as the option. The company cited the track's varied corners and elevation changes when it made that choice.

What happened in practice?

Rosberg topped Friday's timesheets, ahead of the Red Bulls of Kvyat and Ricciardo. The session began on a very wet track, and as it dried, drivers switched to intermediate tyres. Hamilton was fifth behind Sainz, while Alonso was ninth with his new engine, even after running wide late on. Maldonado could not run because of a gearbox problem.

At Sauber, Raffaele Marciello replaced Felipe Nasr and finished three-tenths up on Ericsson.

On Saturday Hamilton was fastest, ahead of Vettel, who spun out twice as conditions worsened. Verstappen ended the session last, while Hulkenberg was third, ahead of Bottas and Sainz.

How did qualifying play out on race morning?

Qualifying was delayed several times on Saturday before being moved to Sunday morning. Jenson Button said the delays were the right thing to do, while Ferrari criticised the paddock for its tomfoolery, including bowling and ballroom dancing between the Red Bull drivers.

Qualifying had three parts lasting 18, 15 and 12 minutes, with five drivers eliminated after each of the first two. Hamilton, Rosberg and Ricciardo set the early fastest times, as the teams fought for places before rain could worsen. Sainz crashed at turn 4 in the first part and brought out red flags, and both Manor cars were eliminated along with Ericsson and Nasr. Vettel finished the first part fifteenth, barely making it through.

In Q2 Rosberg was a little over a tenth quicker than Hamilton. Alonso went faster than Bottas and looked set for Q3 until Verstappen eliminated him. Late spins for aquaplaning followed, and both Lotus cars and the second McLaren missed the top ten. Rain forced the cancellation of the third part, so the Q2 times set the grid.

Rosberg took his third consecutive pole, ahead of Hamilton, Ricciardo and Kvyat. Having been passed by Hamilton in Japan and retired from the Russian race while leading, he said he wanted to win in Austin really badly. A grid penalty moves a driver back from the place his qualifying lap earned. Vettel, fifth fastest, was pushed back by his grid penalty, so Perez and Hulkenberg took the third row. Alonso was ninth, McLaren's highest grid position of the season.

Sainz needed the stewards' permission to start, because he had missed the 107% cut-off set by Ricciardo's fastest lap in the first part. That rule requires a driver to set a time within 107% of the quickest lap, or ask for permission to race. Bottas picked up a five-place penalty after a gearbox change.

How did the race start?

All the drivers began on intermediate tyres, because the track was still wet after rain shortly before the start. Intermediates suit a damp or drying track, while full wets are for standing water. Hamilton got away better than Rosberg and forced him wide at turn one to take the lead. Further back, a collision involved Alonso, Massa, both Saubers and Bottas, and Bottas pitted after the opening lap, and Nasr followed; he was first to fit slicks as the track dried.

Rossi hit Stevens from behind, breaking his rear wing and ending his race. Sainz, starting from the back, profited from the chaos and had reached tenth by the close of lap one.

A virtual safety car followed on lap five to clear debris from the first corner. Under that restriction drivers must hold a set time through each sector, rather than run at race pace. Bottas's race ended on lap seven when a damper gave out after the turn-one contact, and Grosjean retired on lap 12.

Rosberg passed Kvyat for second on lap 8, and a battle for the lead developed between Hamilton and Ricciardo. Ricciardo went around Hamilton on lap fifteen, and as the grip of the intermediates faded, the overtaking came thick and fast. Rosberg unsuccessfully tried to pass his teammate for second on lap 16. Hamilton was the first leader to switch to slicks, stopping at the end of lap seventeen, and Rosberg moved ahead of him on lap 18 as the stops began.

What happened in the middle of the race?

Ricciardo led until the pit stops, and Vettel had climbed from thirteenth on the grid to sixth by lap 12. The Mercedes pair went ahead of Ricciardo and Verstappen around laps 22 and 23. Vettel closed on the leading group and passed Kvyat for fourth on lap 24.

Raikkonen and Massa retired on lap 24 with the same problem that had forced a teammate to stop earlier. Ericsson stopped on track on lap 27, bringing out the safety car.

The safety car let Vettel change tyres, and he moved back into fifth as Verstappen also pitted. He then moved into fourth at Kvyat's expense at the restart.

Hulkenberg tried to pass Ricciardo, and on the following lap the two collided, ending Hulkenberg's race. Ricciardo was able to continue, but he was overtaken by his teammate Verstappen, with Jenson Button behind in seventh. Another virtual safety car was declared to clear his car, and Rosberg decided to pit.

By lap 40 Rosberg had moved up to third at Verstappen's expense, and he passed Vettel on lap 42 on newer tyres.

How did the lead change hands at the end?

Kvyat hit hard at the penultimate corner, which brought a further safety car. Hamilton and Vettel both changed tyres again under it, and the order behind the car was Rosberg, Hamilton, Verstappen, Vettel and Alonso.

At the restart Verstappen tried to pass Hamilton but could not, and Vettel then went by Verstappen. On lap 48 Rosberg slid off the track when wheelspin upset his rear tyres, and he later put it down to a sudden gust.

Hamilton soon opened a gap on his teammate. Alonso, who had been running fifth, lost power and eventually finished eleventh. Vettel edged closer to Rosberg for second in the closing laps, but he could not find a way past.

Which drivers finished where?

Both Red Bull drivers had initially challenged the Mercedes at the front, but they dropped back as the track dried. Ricciardo finished tenth after a race that had been interrupted by safety cars and a number of incidents in the wet.

What did the drivers say afterwards?

Elton John hosted the podium interviews, and Rosberg voiced his disappointment there. He had shown his anger in the cool-down room, and he flung his podium cap back at Hamilton after Hamilton had tossed it to him, which he later called just their typical games.

Vettel was pleased with his performance and said the team had gone beyond what was expected of it. Hamilton, now champion, said his third crown was the highlight of his life, and he thanked his father and family for their support.

Hamilton compared the title to his two earlier ones and said the last two had been climactic in the final race.