Retro: Why the 2011 Chinese Grand Prix was not won by strategy

Posted on April 10, 2012

0


Up until a few days ago, I was under the impression that Lewis Hamilton’s swashbuckling victory in last year’s Chinese Grand Prix was down to McLaren’s decision to change from a two-stop race to a three stop race, and that Hamilton was able to catch and pass the Red Bull of Sebastian Vettel due to being on a better strategy. Obviously, he had to make it work – remember that Jenson Button finished behind Vettel – but the impression at the time was that the underlying pace of Hamilton and Vettel was about the same and that the decisive factor was the strategy. Having done my homework for the 2012 edition of the race by modelling last year’s race, I have come to a different conclusion. Hamilton won because he was faster – pure and simple.

So how can I tell? The modelling work I do in order to assess the races accounts for the changing fuel load of the cars and the degradation of the tyres and comes out with an underlying pace for each of the cars – on each type of tyre. The quality of the model is down to how well the traces of each of the cars can be modelled on a race history chart. The chart for the first six is shown below, with the key aspects highlighted.

As a reminder – the McLarens beat pole-sitter Vettel to the first corner, Button ahead. They then proceeded to run as a threesome pulling away from Rosberg and Massa. Webber, meanwhile, had qualified 18th by dint of a misjudged saving of a set of soft tyres and had started on the harder tyres in traffic. He was losing more than a second a lap in the traffic, and so it was the right call to use the hards on the first stint, and also the right call to put him on a three stop minimising the losses by getting him in clear air early.

Also committed to a three stop strategy was Rosberg – the Mercedes suffering with high degradation early in the season (sounds familiar…), and this call looked inspired when, between his lap 12 stop and the leaders lap 15-16 stops, the tyres went off significantly leaving the leading trio (and Massa) nearly 10s adrift of the Mercedes. But now they were in the order Vettel-Button-Massa-Hamilton as McLaren left it far too late for Hamilton and Button lost time stopping in the Red Bull pit…

It was at this point that McLaren made the call to go to three stops – which left them behind Rosberg on the track, but free of Vettel and Massa. It was at this point that Hamilton began catching Button and his true pace was unleashed. He passed Button, and then pulled away quickly enough to negate the undercut at the final stops. Then he caught and passed Rosberg, Massa and Vettel to win. Button, for his part passed the first two, but was passed by the recovering Webber, who was travelling very quickly on his soft tyres at the end. It is worth noting that all the three stoppers had to pass their respective two-stopping opposition (Vettel and Massa) in the final stint – the two stoppers had track position, which is often key.

So to the point at which we came in – what was the underlying pace of the cars? Well, I can use exactly the same model for Vettel and Button and get a very good fit for both cars. This means that these cars (or car/driver combinations) have underlying pace which is within about 0.1s of each other, which is about as small a gap as the model can believably determine. So, the two stopping Vettel was not beaten by the three stopping Button with an identical underlying pace. Indeed, the fits suggest that without traffic, Button would have been close, but would not quite have caught Vettel by the end (with a caveat on tyre life). The graph below shows this:

By comparison, the underlying pace of Hamilton is a full four-tenths of a second faster. The graph below shows Hamilton’s fit, and how he is much faster once he gets free air, and starts overtaking people.

So Vettel was not really beaten by strategy, but by pure pace.

Interestingly, Massa and Rosberg show very similar pace (about 0.2s down on Vettel), but the three stopping Rosberg catches and passes Massa in the final stint. Looking at the first chart, Rosberg’s pursuit was aided considerably by the time lost by Massa in trying to keep the McLarens behind. This would have been similar to the Button/Vettel picture, but Rosberg started the final stint in a stronger position.

And Webber – what of his pace in the final stint? Fitting his data with the model shows him indeed to be faster than Vettel – but by only 0.2s per lap. Which still leaves Hamilton with a clear margin for the fastest underlying pace in the race.

There are very few races I have modelled where this type of dominant underlying pace is seen in standard dry conditions. It’ll be interesting to see if Lewis can do it again this year.

Advertisements