This was a snakes and ladders type of race, where a driver could get a leg up from a timely Virtual Safety Car or lose ground with a badly timed pit stop. We saw both in the British Grand Prix thanks to a downpour minutes before the off, a Safety Car start and then a Virtual Safety Car soon after the restart.
Lewis Hamilton won the British Grand Prix for the fourth time, a result that was never in doubt from the start, but the battle for second and several other races were close and strategy was decisive. We also saw clearly that the Red Bull is faster than the Mercedes in intermediate wet conditions, which could give them a platform for a win later in the season. Conversely it showed how much Williams struggle for performance when the track is wet. Neither car finished in the points despite starting sixth and 12th on the grid.
Pre Race Expectations
Friday practice running was not interrupted by rain and the teams covered a good mileage, all struggling to make sense of the hard tyre, which wasn’t fast enough relative to the soft and medium and gave a shorter life than the medium.
For some cars it gave more stability in high speed corners, but otherwise it was a tyre to avoid. The likely strategy, had it stayed dry, was to do an opening 10 lap stint on softs, then two stints on medium.
Ferrari had not saved a second new set of medium tyres, so they could have been caught out badly in a dry race, but they got away with it because it poured down with 15 minutes to go before the start.
First transition from wet to intermediate tyres
Although there was some disappointment with the length of time the Safety Car stayed out at the start of the race, we still had a variety of different decisions made by teams and drivers as to when was the moment to move from full wets, to intermediates and then onto slick tyres. And these proved to be critical to race results in some cases.
Everyone followed the same pattern through these transitions, with a few laps of variation. All the cars ran on the medium compound slick tyres once the track was ready for it. Unusually it was Ferrari’s Sebastian Vettel who gambled first on the move to slicks, as he was trying to make up for a five place grid penalty and not having taken advantage of the first switch from wets to intermediates.
Vettel had been running just behind Sergio Perez after the restart on Lap 5 in 10th and 11th places. Vettel went for intermediates as soon as the Safety Car went in, but Perez delayed the move to intermediates by two laps, like the three front-runners, Hamilton, Rosberg and Verstappen.
It paid massive dividends. One of the first cars to take intermediates, Pascal Wehrlein in the Manor, went off into the gravel and a Virtual Safety Car was deployed. This offered those who had yet to pit and chance to stop at reduced speeds and saved 10 seconds compared to those who had pitted at racing speeds.
This ‘snakes and ladders’ moment cemented the position of the top three at the front and catapulted Perez from 10th to fourth, ahead of Red Bull’s Daniel Ricciardo.
Teams have very sophisticated tools now for measuring relative performance of all the cars on track at a moment like this and the ‘guinea pigs’, who take the early gamble are monitored closely by two or three strategy engineers in each team looking for improvements in pace sector by sector and areas of the track which are not suitable yet for intermediates.
The teams who delayed their stop for intermediates by one or two laps were the ones closely monitoring this and judging the conditions not to be right yet for that tyre. At the front there are other factors at play on a wet track. One is the ‘spray effect’, which means that the less spray you are driving into, the less time you lose. Cars in the midfield lose a lot of time.
There is no need to react pre-emptively, which is why both Mercedes and Red Bull, the top four cars, did not pit straight away after the Safety Car. The cars that went early got it wrong in this case, but a gamble can work in some situations so it’s deemed worth a try to get that snakes and ladders boost up. What was strange with Ferrari again, was that they pitted both cars on Lap 5, taking the same gamble with both. Most teams avoided that, giving one car the early gamble and bringing the other car in a lap later.
No one could have certainty at the moment when the Safety Car was released, before they had done a lap in anger. So it’s a risk to take intermediates, but Ferrari didn’t split their risk, they went for it and it cost them the upside enjoyed by drivers like Perez, and Massa who gained six and five places respectively. Vettel stayed 11th and Raikkonen lost a place.
Second transition Intermediate to medium tyres
By Lap 15 the track was drying enough to consider switching to slick tyres. Vettel went for it first and over the next three laps everyone else followed. Vettel spun, which indicates that he went a lap too early, while Verstappen tried to use the phenomenal pace of the Red Bull on worn intermediates, to do an extra lap and close on Hamilton, who had pitted on Lap 17. He had passed Rosberg using that pace on Lap 16 around the outside of Becketts, finding grip the Mercedes struggled to find.
Mercedes pitted both drivers on Lap 17 and straight away Hamilton was in the low 1m 40s, while Rosberg took several laps to adjust to the slicks and dropped five seconds behind Verstappen, who was straight onto Hamilton’e pace from the outset.
As the stint went on and the track dried out, Rosberg got more comfortable and the Mercedes reeled in the Red Bull and overtook. The whole field chose the medium tyre for their stops; with around 34 laps to the finish it was the best compromise between pace and durability. The soft would have grained and another stop would have been needed, while the hard was 0.5s per lap slower than the medium and lasted two laps less, so was unattractive.
It wasn’t certain that the medium tyres would make it to the finish from there, but Verstappen again did well to make it to the chequered flag as the Red Bull had been harder on the tyres than the Mercedes in practice. The strategists monitor the tyre performance in the stint and with 15 laps to go, the window when they would need to make another stop, the data said that the tyres would be okay to the finish.
Perez’ result in sixth place was built on that early decision to delay the first stop, but credit to Hulkenberg to recover and finish behind him, having dropped from 8th to 10th through that first transition, but he climbed up to seventh through making his second stop a lap later than Kvyat and Massa.
