The UBS Race Strategy Report is written by James Allen with input and data from team strategists and from Pirelli.

Interlagos, Sao Paulo, November 25 2012

The FORMULA 1 GRANDE PRÊMIO PETROBRAS DO BRASIL 2012 was a rollercoaster of a race, with positions and fortunes changing from lap to lap as intermittent rain caused chaos. Sebastian Vettel managed to survive a first lap collision, a broken radio and four pit stops to fight back from 17th place on lap one to sixth at the end to secure the points he needed to win the world championship for the third time.

Fernando Alonso, meanwhile, went from seventh on the grid to second at the end, but did not have the pace in the Ferrari to challenge Jenson Button for the win, which would have given him the points to clinch the title.

With conditions so hard to predict and so changeable this was a day when the strategists were reacting to events and working on instinct. For some, with nothing to lose, it was worth taking a gamble on a tyre choice. For the two title contenders it was all about being certain to be there at the chequered flag with as many points as possible.

The race fell into three distant phases. The early laps when it began to rain and a decision needed to be made whether to pit for intermediate tyres or stay out on dry tyres. A middle part of the race when everyone was on dry tyres, and then the final 20 laps in the rain, when everyone moved to intermediates.

Rain had been forecast for race day all week. However, in the hours before the race the chance of rain was receding from 80% to 40%, as teams faced up to the possibility of a dry race and very different conditions from practice and qualifying.

The key factor was always going to be the temperature, it was cool on race day, but if the temperature kept rising it would mean more thermal degradation on the tyres and therefore more pit stops.

There were three cars out of position; Maldonado in 16th after his penalty for missing a weight check, Grosjean in 18th after hitting de la Rosa in qualifying and arguably Rosberg, who had overqualified in the Mercedes in 9th place and was set to fall back in the race.

Indications were that teams would go for a two stop strategy with the first stop around lap 20-25 with a middle stint on a new set of hard tyres and then review performance before deciding whether to switch to used mediums for the last stint or another set of new hards.

However the track conditions before the rain began were different from Friday practice where the track temperature was almost 50 degrees, compared to less than half that on race day. So even without rain, teams were set for a reactive strategy.

Once again Pirelli’s tyre choice had been conservative, the Italian firm opting for the hard and medium tyres because of several high energy corners. The hard tyre was well out of its optimum working range in the 50 degree track temperatures during Friday practice and there were signs of blistering. But on race day with lower temperatures, the hard tyres were better suited.

Going into the race, only Di Resta of the leading cars had a new set of mediums left, while Ferrari only had one new set of hard tyres, compared to the two new sets of Red Bull and McLaren. The Ferrari also had a deficit of around 0.3s to 0.4s in pure car pace to deal with. The team had split its long run tests on Friday, with Massa running the medium and Alonso the hard tyres, so they had plenty of data on which to base their strategy. It was clear that they favoured the medium tyre on race day as they and Lotus were the ones to move onto it in the dry.

The conditions in the early part of the race were difficult, but the teams were ready to react as far as strategy decisions were concerned.  The key strategy call was to stay out when rain started to fall in the early stages with the dry tyres, but few teams were able to do that, as they could not generate enough temperature in the tyres.

Several teams split the strategies at this point, around lap 10; putting one driver onto intermediates and leaving the other on slicks. Red Bull put Webber onto intermediates, for example and then switched Vettel onto them a lap later. For McLaren Hamilton went onto the intermediates, but Button resisted.

There was a brief moment in this phase when it looked like Button and Nico Hulkenberg were on the wrong tyre, with the slick. But then drivers who went onto the intermediate tyres too early suffered from graining.  So it swung back Hulkenberg and Button’s way and when the drivers who had switched to intermediates were forced to pit again around lap 18-20, it left Button and Hulkenberg over 40 seconds clear of the field, having made no stops compared to the two made by the others.

It is worth noting that Force India has something of a track record on tricky wet days like this of copying what Button does, as he has an uncanny knack of being on the right tyre at the right time and there have been several occasions when Force India has matched his moves and got a strong result.

In this instance both Button and Hulkenberg were able to get sufficient temperature into the tyres to deal with the water on the track, although there was a thin dry line for most of the early stages of the race. This made overtaking difficult because off line there was no grip and several cars went straight on instead of out-braking their rivals.

It was only later that the track became fully wet, after lap 50, when the whole field went for intermediates.

The decisive moment of the race was the deployment of the safety car on lap 23 due to the debris on the track, which had led to a puncture for Nico Rosberg. This greatly helped Hamilton, Alonso, Vettel, Webber and others who had lost ground early on through pit stops and spins. It wiped out the lead of Button and Hulkenberg and brought Hamilton into their battle, which ultimately led to the collision between Hulkenberg and Hamilton.

The pair had no choice but to pit under the safety car and retain their lead, but with a bunched up field behind.

Incidentally, in phase two of the race, around laps 18-20, when everyone moved back onto dry tyres, Ferrari and Lotus went for the medium tyre while most went for the hard. For most, this was a hedge in case they needed to go to the finish on that set of tyres, with over 40 laps remaining. 

Lotus were prepared to go to the end on the mediums, given their better tyre usage, but Ferrari would have struggled as they suffered obvious graining on the surface of the front tyres. 

Most F1 strategists said after the race that it was relatively clear what was the right move to make at each phase of the race, but what prevented more of them from copying Button and Hulkenberg was confidence that they could generate the tyre temperature.

Button is a past master at these situations, but it was interesting to note, once again as in Brazil qualifying in 2010, that Hulkenberg has the knack too. It was regrettable that he lost control of the car trying to pass Hamilton later in the race and got a drive through penalty for it, as it overshadowed an otherwise exceptional performance and great strategic reaction.

N=new: U=used; M=Medium; H=Hard; DT= drive through penalty

Note: The large dip in the centre of the graph is the first safety car period and the dip at the end is the second safety car period.

The UBS Race Strategy Report is written by James Allen, with input and data from several F1 teams and from Pirelli.