Japan in Depth: Could four stops have worked for Red Bull?

Posted on October 10, 2011


Sebastian Vettel was pulling away from Jenson Button at 0.4s per lap for the first six laps, demonstrating the pace advantage of the Red Bull. Then his tyre degradation became severe. In his second stint, his underlying pace was much slower, as he tried to get the tyres to last long enough to stay on a three stop strategy. As we now know, it didn’t work out for him. But what if Red Bull had gone for four stops?

First, we need to understand what actually happened. Below we see the race history chart up to the safety car deployment with the data (in solid lines) and the intelligentF1 model fits (dashed lines) for the first three finishers. The curves can be seen to fit the second and third stints very well. Vettel can be seen to have lost some time in the second stop, this is clearly due to his tyres running out of performance and a slow lap before the in lap, as well as spending longer in the pits putting him behind Button.

As these fits are good in stints two and three, we learn a number of things. Firstly, Vettel used his new set of option tyres in the second stint, Button and Alonso used theirs in the third stint (this is why Red Bull made the final stop earlier).  This means that Jenson was actually slightly faster on used primes than Vettel on new primes at this stage of the race. The interest, however, is in the first stint where the curves don’t match. The pace is given by the gradient of the curve, and whilst the model does reasonably well with the McLaren and Ferrari, the slope is not close to the Red Bull curve. This is due to Vettel’s underlying pace (on which the intelligentF1 model is based) being 0.9s faster in the first stint than on the later stints on options. Therefore it is clear that Red Bull were holding back on pace in order to hold onto the tyres. As Seb’s new tyres only lasted as long as Jenson’s new ones, we can say that this didn’t work out for the new world champion.

But what would have happened if Red Bull had decided to go the opposite route – to use their pace advantage, but to go for four stops. Then the model of the race up to the safety car would look more like this:

On the assumption that the other teams would not have covered Red Bull’s early stop, as their fastest races were three stoppers (sufficient option tyre lifetime), Vettel would have had around a 14s lead if he went for a stint of eight laps on the new tyres, and then seven on his last set of used options before the safety car came out. Would he have been able to stop under the safety car and resume in the lead? Touch and go, but he would certainly have come out ahead of Alonso.

Let’s assume that he didn’t quite make it. What then? Well, the final stint analysis from the intelligentF1 model shows that Vettel had about a 0.3s advantage on the prime tyre over Button, and his new primes would have been slightly slower than Button’s tyres after the safety car, but would have lasted longer. The race history chart after the safety car is below. Again, the real data is in the solid lines, with the intelligentF1 model in the dashed lines.

From the real data, we see that Jenson’s tyres began to struggle just before the final stop, which the intelligentF1 model is able to model with 0.3s extra degradation per lap in comparison with the normal ‘phase 1’ degradation. After the stop Jenson’s pace is faster than the pursuing Ferrari and he is able to pace himself to the end – as can be seen from his data trace becoming less steep. Interestingly, Alonso is gong slower than his full pace as he is defending from Vettel, but after Vettel’s ‘traffic incident’, the gap allows him to increase his pace and to use up the extra tyre life saved by going slower than full pace (this effect seems to be very repeatable with the Pirelli tyres).

But what if Vettel was on a four stop? The intelligentF1 model fit shows that he would have been right behind Button at Jenson’s last stop, and then it was a straight race on the prime tyres. Vettel’s pace advantage almost exactly offset by Button’s new tyres. It would have come down to the pit crews. But had he not come out ahead, Sebastian would almost certainly have come out second, and would have troubled Jenson to the flag.

So four stops would have been better for Red Bull given the assistance from the safety car. But would they have been able to beat Button? Maybe.