The Spanish Grand Prix at the weekend was a relatively straight forward affair in strategy terms with the main decisions on tyres pretty clear with little room for variation. But there were some key decisions to be made on the timing of the pit stop, with positions to be won and lost and the second set of tyres to be maintained over a long period.
Bridgestone brought with them the soft and hard tyres from their range and it was clear that the soft was the better qualifying tyre. This meant that all the top ten started the race on the soft tyre on which they qualified, while all but one of the others also chose to start on the soft.
Only Lucas di Grassi took a chance on the hard tyre, with the intention of running a much longer first stint than his rivals, but he found the car unbalanced on them and pitted on lap 19, which meant he had to do the remaining 47 laps on a set of soft tyres.
The key decision was when to make the first stop. With no refuelling this year making the strategy more one dimensional, the timing of tyre stops is one of the few opportunities for overtaking, especially on a track like Barcelona. Also the earlier you stop the more work you are asking the hard tyres to do. Many drivers ended up doing fifty laps on the hard tyre.
Generally in a tight battle the driver who pits first is the one who gains the advantage, as he has a new set of tyres for a lap or two before his rival pits. But as we saw in one case, when the switch is from soft to hard tyres, that is only the case if the driver can get his hard tyres up to temperature straight away.
Michael Schumacher pitted early, on lap 14 at which point he was four seconds behind 5th place Jenson Button. Button stayed out a further two laps, but when he rejoined Schumacher was right there and took the position. Schumacher had problems getting the hard tyre to switch on and the Mercedes didn’t work well on it for the rest of the race, but it turned out to be academic because fate had handed him an opportunity.
Button had lost six seconds in the pits, “There was a problem with the clutch dragging, so the guys couldn’t get the wheel on, and then I had wheelspin,” he said.
Afterwards Schumacher said that he could have gone longer on the soft tyre and many of the front runners did; Lewis Hamilton, Adrian Sutil and Mark Webber went to lap 17 with the tyres still giving good lap times. Bridgestone’s Hirohide Hamashima said that in his opinion the soft tyre was capable of much longer stints than we saw. Trulli went 22 laps and was setting very consistent lap times in the run up to his stop, while Chandhok went to lap 27.
But it was noticeable that not everyone had as good a balance on the hard tyre as on the soft. Webber’s Red Bull certainly did and Alonso’s Ferrari was actually better on the hard tyre. But it seemed that other teams had prioritised qualifying and getting the best from the soft tyre, knowing how hard it was to overtake once the pit stop was done – a fact proved by Schumacher holding Button back despite Button’s car being two seconds a lap faster on the hard tyre.
Sebastian Vettel lost a place to Lewis Hamilton in the pit stops and afterwards admitted that this was a decision they had got wrong, coming in earlier than was necessary. He stopped on lap 16, when he was 2.6 seconds ahead of Hamilton, who pitted a lap later.
Like Button, Vettel lost time in the pits, being held back by the chief mechanic so as not to collide with Alonso as he entered his pit box. This was just bad luck, but once he went out Vettel also found it hard to warm up the hard tyre. His out lap was 2.4 seconds slower than Hamilton’s, which was enough to put him in Hamilton’s range as he exited the pits and after a side by side battle in Turn 1, Hamilton took the place.
Interestingly, Vettel’s out lap on the hard tyre was four seconds slower than Mark Webber’s in the same Red Bull car.
So in retrospect Vettel would have been better off staying out longer and either pitting at the same time as Hamilton or even a lap later.
In Monaco this weekend there will be a lot of important decisions to be made, not least in the timing of qualifying runs and pit stops. With overtaking virtually impossible at Monaco qualifying, the start and the pit stops will determine everything.