Chinese Grand Prix: Why the pitstop didn’t cost Button – and how McLaren could have challenged Rosberg

Posted on April 16, 2012


There is a huge amount of work to do to dissect such a complex (and gripping) race as the Chinese Grand Prix. Trouble is, I find myself watching the action when I’m trying to do analysis. The last ten laps are as much fun as any race in the last twenty years. Great stuff. So, as I’m a little pushed to get the full ‘Story from the data’ race report out today, I thought I’d write a shorter post on the relative merits of the two-stop/three-stop race, and make it clear that Button was not going to challenge Rosberg in the final stint if his pitstop hadn’t gone wrong. I’ll try to get the full report out tomorrow.

So firstly, the easy job. Button’s pitstop. Using the model I’ve developed here, I can infer the underlying pace of the cars on each type of tyre – and I can be pretty confident if I can match the pace in two different stints for a number of cars when using the same fuel model. The good news is, for the Chinese Grand Prix, that the fits of pace are excellent for most of the cars – even with the overtaking chaos. Therefore, having calculated Button’s underlying pace, I can predict his speed in the final stint of the race (which nicely matches his laps in clear air) and see what would most likely have happened if he had not had a problem in this pitstop. Adding this line (the dotted line) to the race history chart for the second half of the race, we get the chart below.

So we can see that Button would have put some pressure on Rosberg, and would have been catching him at just under a second a lap towards the end, but would fall just over three seconds short. It is possible that given a sniff of a win, Jenson may have been able to eke out a little more pace, but Rosberg also slowed a little over the last 10 laps or so. It is incredibly unlikely that Button would have won, even without the pitstop problem.

So how could he have won? Well, let’s assume that Mercedes needed to make the first stop when they did, and didn’t just cover everyone else. There is a little bit of guesswork in this, but given that Perez only went three laps further, it seems that Mercedes wouldn’t have been able to hold off long. The fact that Schumacher was holding up the chasing pack (and he was holding them up) gave Rosberg the break. If Button had made his stop as late as he could to get out ahead of Webber (same lap as Rosberg stopped, by coincidence), he would have had the chance to challenge Rosberg on the faster (partly due to traffic) two-stop strategy (with two stints on mediums). He would have got very close as shown in the chart below.

So Button could have got very close – but perhaps would not quite have had enough. But what of his team-mate? It wasn’t evident in the race, but the analysis I’ve done suggests that his underlying pace was about 0.1s up on Button on the soft tyres and three tenths quicker on the mediums. So what could have done if he were able to make his tyres last on a two-stop? Using the same logic, Hamilton had the pace to have got close enough to Rosberg in the second stint to have had a shot at the undercut at the final stops. This is shown in the chart below.

Admittedly, this is dependent upon Lewis being able to get out ahead of Webber, and on Schumacher pitting to allow him a lap in clear air to do that. However, what it does show is that had his gearbox not needed replacing, and had he got into the first turn in second place behind Rosberg, he would have been a very heavy favourite to beat the Mercedes driver to the win. It wasn’t clear watching the race, but one of the fastest two drivers in this race was Hamilton (the other was Mark Webber). The gearbox penalty cost.

I don’t want to take anything away from Rosberg’s drive as it was superb, but he was not as dominantly quick as it appeared. McLaren could well have won this race had circumstances (and strategy) been different. In fact, with a decent start, Mark Webber could also have won it.