Korean Grand Prix: Strategy Predictions

Posted on October 13, 2011

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After Bridgestone’s experience with graining at last year’s Korean Grand Prix, everyone was worried about the tyres. A wet race, significant amounts of which were behind the safety car meant that we never got to see how that played out. It’s looking like a dry race this year, and Pirelli have brought their soft and super-soft tyres. All the doomsayers are talking about four stops (I’ve seen one quote suggesting using all six sets of tyres!), on the assumption that tyre life limits everything.

The basic starting point data for the Korean race is a little hazy, given the inclement conditions, and the amount of time spent behind the safety car, last year. From the data that does exist, the fuel penalty looks like about 0.09s per lap and the pit stop loss of the order of 24s (I’ve seen 23s quoted, but the best of the few stops from last year’s event was about 25s). Based on recent experience, the prime tyre is likely to be much slower than the option tyre in qualifying, but perhaps only 0.5s slower for the bulk of a stint. So we’ll take this as our starting point, and put it into the intelligentF1 model. If the tyres last as long as we like so that the fastest race is limited by the relative pace of the tyres and not the tyre lifetime, we get the chart below (1 stop is in blue, 2 stops in dark grey, 3 stops in red and 4 stops in light grey) assuming that as many sets of options as possible are used:

From this, it would be a two stop race, on a standard option-option-prime strategy. But we know that the tyre wear is likely to be significantly worse than this. So based on the tyre performance in Singapore, we can put a ‘phase 2’ degradation model into the predictions. This gives us about 1s per lap degradation on the option and about 0.3s on the prime once we hit the additional degradation phase. An optimistic estimate would be that the primes last 25 laps, and the options 15 laps before ‘phase 2’ starts. This changes the picture dramatically.

The additional degradation can be seen in the way the curves droop. So a one-stop would be out, but two or three would be competitive, with four just about an option. What if the tyre performance is worse, especially for the options, say 10 laps for the options and 20 laps for the primes? Then the advantage shifts to being on the prime tyres for longer. The one stop in blue has been converted to a two stop, but option-prime-prime. It does substantially better than option-option-prime based on this model. Three stops is competitive, but it’s better to do two stints on each type of tyre, which is the model shown on the chart. With the relatively large time loss for a pit stop, four stops is still not quite there. (I’ve changed the reference time so the lines don’t start disappearing off the bottom of the chart)

So finally, what if we have a situation more like that faced in Turkey, with the options good for 8 laps, and the primes good for about 12 – with ‘phase 2’ degradation upped to 0.5s per lap on the primes? Then, the intelligentF1 model gives us a picture with four stops being competitive, but it’s had to get quite serious for that to be the case.

Due to the large pitstop time loss (which does need verifying), it will take real problems with tyre degradation to make this a four stop race, let alone five stops. Obviously, we won’t know how bad the degradation is until Friday, or if it rains, Saturday, but it seems that things would have to be very bad for everyone to be four-stopping. It is of course possible, but I’m not convinced. Let’s see how they go.

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