When Mark Webber entered the pit lane on lap 48 of the Singapore Grand Prix, it was almost inevitable that Jenson Button would cover, and then Sebastian Vettel would cover him. But what would have happened if Jenson had stayed out? Would it have been an inspired risk, or a disasterous mistake? Modelling the race after the safety car restart, we can project what is likely to have happened. Let’s start by looking at what actually happened and the intelligentF1 model of the underlying pace. From this, it can be seen that Vettel had some pace in hand, and Webber backed off once Jenson had covered him and demonstrated that he had the same pace.
But what if Jenson had stayed out? All the cars that non-stopped after the safety car entered what most teams call ‘phase 2’ where there is significant additional tyre degradation. If we base the ‘phase 2’ degradation of Jenson’s tyres on the Force India of Paul di Resta, who suffered the least of those in clear air, then we get the scenario shown below:
And the answer becomes obvious. Even if Button was able to weave his magic and make the tyres last a little longer than anyone else, he would still have been in trouble, and Webber would have had a very good chance of catching him. On catching, the pace difference would have been more than 4s per lap, and Mark would have been through for a Red Bull 1-2. So Jenson had to stop.
Out of interest, the model also predicts that Vettel was so far ahead that he would have won it either way.