Chinese Grand Prix: Strategy with an unexpected grid order

Posted on April 14, 2012

2


Qualifying for the Chinese Grand Prix may have provided little surprise in the battle between Hamilton and the Mercedes cars for pole, but with Lewis’ penalty (he starts 7th), it is very difficult to predict a winner. Were Hamilton to start second, he would be a heavy favourite, and he could do it on a standard strategy. The Mercedes struggled with their tyres in practice, and were slower than pretty much the rest of the top ten in the race simulations. But what difference does it make having the fast race cars not at the front at the start of the race?

We know that the Mercedes cars are very fast in a straight line. And that they are very fast with the DRS deployed. Therefore it is entirely possible that Rosberg and Schumacher could keep the rest of the field behind them depsite being quite slow in the opening laps of the race. So, if you are a faster car, what is the best way to get past? And how much of a risk is it?

From the analysis in the previous post, two stops and three stops would be very similar on pace (two stop is just faster, but only if the tyres last long enough), given that there is no time lost in traffic. However, it is the precisely the time lost in traffic which we would like to assess. On the face of it, there are two choices – stop early and undercut (probably requiring three stops) or to stay out later and make as much time up as possible in free air, although this way it may be difficult to make up enough time not to require an on-track pass. The advantages of the early stop are the undercut possibility (which removes the overtaking problem until you catch the Mercedes again), but there is a possibility of falling into other traffic where more time will be lost. If there is a train of cars behind the Mercedes, time lost in traffic may mean that you get ahead of the Mercedes, but find someone else ahead of you! It may be that whoever gets this right at the first stops will be able to control the race.

Let’s look at the possibilities. I’ll assume that Mercedes are going for two stops (as this makes them harder to pass) and will need to use the harder medium tyre at the first stop. The options are two stops (especially if the tyres last well) or three stops. The issues are having to pass the Mercedes on-track, and not getting stuck in traffic. The simulated race history chart looks like the one below:

The assumption is that the race pace of the Mercedes is 0.7s per lap slower than the ‘fast car’ (this is the Hamilton-Rosberg gap from Friday practice) and that the back of the midfield is 1.5s down on the ‘fast car’. The Caterhams are about 2.5s slower. The two stop race assumes that the soft tyres do 20 laps, and so there is a risk that the tyres won’t last quite that long. The back of the midfield should be at least 10s down on the leader on the first lap, and the Caterhams are usually at about 15s. This gives us an expectation of where they are likely to be towards the end of the first stint. This is all done without reckoning on the battles between the cars trying to get themselves ahead of the slower Mercedes, which will (of course) complicate things immensely.

The risk for the three stopper is twofold. Firstly, they could (just) get stuck in the midfield after their first stop. However, the pace advantage on new tyres will be such that passing will be easy, but time can still be lost. Also, it is likely that the Mercedes would be caught towards the end of the second stint – there will be a sufficient pace advantage to pass (order 2s per lap), but time is sure to be lost. On the other hand, the chances are (as long as you don’t get undercut) that you will be able to run at your true pace, and not be stuck in the queue of cars trying to jump the Mercedes.

For the two stopper, they will need to go at least two laps further than the Mercedes without hitting the phase 2 degradation to get out ahead of the Mercedes cars. This looks to be possible, but is by no means certain. If this can be done, then they would not have traffic problems, nor have to pass the Mercedes on track. It would certainly mean falling behind the three stoppers in the second stint, but is essentially a quicker strategy overall. The big question is whether the teams have the confidence in both their pace and their tyre conservation to think that they can go fast enough for long enough to jump the Mercedes at the first stops – especially given that the Mercedes team have produced very fast pitstops in the last year. The problem here is that this works if you are at the front of the following queue (so get free air), but not if you are further back in the queue.

I expect to see both approaches used – it really depends how quickly Mercedes get into tyre trouble. If they have to go for three stops, it may well be that the other teams can jump them simply by doing a stop fewer. In which case it pays to get to the front of the queue chasing them.

This race could be decided by the strategists at the first stops. And there will be some luck involved. I would guess that all the teams will be wanting to do it on two stops, but it will be fascinating to see who pulls the trigger on three stops. And if it works out.

Could be a good one…

Advertisements