Chinese Grand Prix: Story from the Data

Posted on April 17, 2012


This is a complicated one. Usually, the gaps between the cars become large enough that the analysis can be done a few cars at a time, and traffic effects are mainly significant in the first stint. But here, and this is entirely due to the fact that F1 2012 is extremely close, pretty much every car was trapped in traffic for enough of the race for this to be a determining factor in nearly every car’s finishing position. Outright pace counted, but as the pace of the first eighteen cars is covered by less than one second, and a pace advantage of about a second was needed to get by, the amount of time lost in traffic made all the difference. Track position counted for as much as pace. And in these circumstances, the difference between two and three stops (around 3-10s) is dwarfed by the time lost in traffic (around 20s for many cars). Everyone (bar Rosberg) was significantly held up at some point. As I said, complicated. Have a look at the race history chart – I’ve zoomed in on the battle for second (to about 15th). There’s a lot going on. What’s worth noting is that in clear air, the lines are close to straight, but where there is action, there are wiggles which always show lost time.

Let’s start with Rosberg, as he is the easiest. He had two major allies who turned his getting into the first corner first into a commanding victory. They are Michael Schumacher and Mark Webber. The data analysis shows that nearly all the cars who ran on soft tyres later in the race were faster than Schumacher’s first stint in underlying pace. Indeed, the McLaren’s second stint on softs was equivalent to Rosberg’s first stint in underlying pace. The Schumacher buffer made a big difference. It also kept the field bunched. After 10 laps, the gap between the Mercedes was nearly 5s, and the gap between Schumacher (2nd) and Maldonado (15th before anyone stopped) was only 13.5s, or about two-thirds of a pitstop. This meant that anyone behind Schumacher was going to have trouble with traffic if they pitted.

The ideal thing, therefore, would be to stay out longer than the Mercedes as tried by Perez and Massa. Their strategies failed due to being slow on the mediums in the second stint (in the case of Perez) and starting on the mediums which were slower than the softs, and so dropping back too far after the first stop (in the case of Massa). As demonstrated in yesterday’s post, this could have worked very well for the McLarens.

However, it would not have been so good for the Red Bulls if everyone stayed out – as they were stuck in 9th and 14th places at the start. So they needed to do something to get some clear air, and to shake up the order. Making the call to stop Webber on lap six was a calculated risk. If no-one followed they got some clear air, but would have had some overtaking to do in the final stint. If everyone followed, they would have gained from the undercut. As it turned out, most did respond, but a little later. Which meant that the major traffic happened for Webber in the third stint, but he had gained much time by then.

So how did this help Rosberg? Well, it meant that the cars behind were covering each other (both McLarens covered Webber) and Rosberg was able to stop late enough to do a two stop without having to take any risks on tyre life. The only threat to him was removed once the McLarens committed to three stops by taking softs for the second stint. If they had gone for mediums, and hung on for two stops… But that is the story of yesterday’s post.

To try to make things easier (and there is no perfect way of doing this), I’m going to break up the race into three – loosley based around the stints of the two stoppers. The first segment of the race, which is about 25 laps, is shown below. I have highlighted some points of interest.

After the first set of stops (in reaction to Red Bull) have shaken out, the cars which are being held up are Vettel (behind Grosjean – and only a small amount), Grosjean (behind Kobayashi) and the Williams (behind Force India/Sauber – we won’t see their real pace until later). Once Massa stops, he is also trapped behind a Force India. Senna was matching Vettel/Grosjean until he didn’t get past Perez. At this stage of the race Sauber went from chasing podiums to scrabbling for points as they had poor pace on the medium tyres (about 0.6s down Rosberg just to show how slow it is in absolute terms – things are close). The timing of the second stops of Webber and Hamilton are interesting as it drops them to the back of the pack, with no clear air. We’ll see more on the next chart as the two-stop/three-stop issues start to play out.

There are a number of battles which are decided in this phase. The first is the fight between the McLaren drivers. A few extra laps from the soft tyres for Button means that he has to pass three fewer cars than Hamilton and the gap between them more than doubles despite Hamilton having had new tyres for two laps. Alonso undercuts Raikkonen, and his team mate lets him by to run at a good pace. The Lotus, however, is trapped behind the Ferrari, and restricted to its pace the team make the brave call to switch to a two stop and see if they can hang on. Once he has caught Massa, the beginnings of the big car queue are in place. Each successive stop now puts a car behind the front of this queue with the new tyres and small underlying pace differences meaning that the queue is going to get longer.

Next to join is Vettel, who was beginning to drop away from Grosjean, undercuts the Lotus, and joins the queue ahead. It is at this point that the Williams, on their two stop, start to look good. They get some free air after their final stop, and their pace sees them join the queue either side of Webber, who has lost time (with Hamilton again) behind the struggling Sauber of Perez. Alonso, who had a nice run in free air after Massa let him by is able to catch Hamilton who didn’t, and once they pit they join the queue behind the Red Bull of Webber.

And so the stage is set for the final act. Cars on older tyres ahead of cars on newer tyres. Small variations in pace, although these do make a difference come the end. I guess this comes down to good old-fashioned racing. Rosberg is home free, Button drops into the pack with a pitstop problem. Webber is ahead of Hamilton and Alonso. And how well will the tyres of Raikkonen, Vettel, Grosjean and the Williams last? Massa pits, freeing the queue, and the race for second is on. It looks like this:

This chart does not replace the action (which was great), but I hope that it helps to show how the action came about. Hamilton and Alonso drop in towards the back of the queue, behind Webber, and Button towards the front. Once through the (pretty quick) Williams cars, with Grosjean accounting for himself, we have the race we saw on screen. Raikkonen sinks without trace (inducing the mistake which cost Webber a podium place), and Vettel also eventually succumbs. Alonso never gets past Maldonado as this Williams is seriously quick – if you look at the traces Maldonado is always faster than Senna – he just seems to get held up, drop back, and catch his team mate again. It is not that surprising, then, that Alonso got stuck. Grosjean, on older tyres, would probably have been passed by Hamilton/Webber anyway had he not been off, but had they needed to fight him it may have been enough for Vettel to hang on to a podium slot. On such small things…

So a huge amount happened. Fortunately there is enough running in clear air to get a picture of the realtive pace of the cars on the medium tyres – there is not really enough on the soft tyres – and most of that is masked by the pace of Schumacher in the first stint. We can tell that the McLarens were as fast as Rosberg as they did another stint on the softs, and not much else. But, as to who was quick on the mediums, it looks like this relative to our race winner:

Hamilton/Webber -0.3s

Maldonado -0.2s

Rosberg/Button/Vettel/Raikkonen/Hulkenburg +0.0s

Grosjean +0.1s

Vergne/Senna +0.2s

Alonso/Massa/Di Resta/Ricciardo +0.4s

Perez +0.5s

Kobayashi +0.6s

Petrov +1.2s

Kovalainen +1.6s

Glock +1.9s

Pic +2.1s

De La Rosa +3.2s

Karthikeyan +3.4s

What stands out is the pace of Maldonado – there is a caveat that he didn’t keep this going for more than a few laps at a time, and he didn’t make forward progress, but he was extremely quick in places. Also worth noting is the pace of Massa. He was as quick as his team mate here, although I don’t suppose many people will notice. Also, Hulkenburg’s pace in his long final stint from way back was superb. I guess no-one noticed that either. Credit to Caterham and Marussia as well. This pace would have put them in the midfield last year. The gaps are closing.

Three races, three different winning cars, and two-thirds of the field within a second of the pace. With a bit of strategy variation, we get races like the Chinese Grand Prix. Here’s to much more of the same in 2012.