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Steering through the chaos: How tyre failures dictated the results of British GP

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Steering through the chaos: How tyre failures dictated the results of British GP
Jul 2, 2013, 11:31 AM

The 2013 British Grand Prix will be remembered for the series of catastrophic tyre failures which befell five of the competitors during the Grand P...

The 2013 British Grand Prix will be remembered for the series of catastrophic tyre failures which befell five of the competitors during the Grand Prix and which had an inevitable bearing on the way that the strategy unfolded.

Although tyre failure was the reason why Lewis Hamilton did not win the race, and a gearbox problem denied Sebastian Vettel, there is no doubt that the positions behind the race winner Nico Rosberg were decided by strategy in the closing stages.

Two safety cars played their part as did an inevitable sense of caution on the part of the teams when deciding their strategy in response to the dramatic tyre failures going on around them.

Pre-race expectations

Although Sergio Perez experienced a left rear tyre failure in the final practice session on Saturday morning, there was no real suspicion that this might become a theme of the race.

Teams had lost Friday morning practice to rain, but managed to do plenty of dry running in the afternoon session so had a decent picture of the relative performance of the medium and hard compound tyres for the race.

Pre-race predictions said that two stops was a faster strategy than three by five seconds, but it was close. On three stops drivers would be able to go flat out, while two stops would require some tyre conservation. There was plenty of flexibility built into the strategies to allow a switch, but to run an ideal three stop you would ideally want to pit for the first time around lap 10, while lap 14 was the target for two stoppers.

The game changer

Lewis Hamilton’s spectacular tyre failure on lap eight set the alarm bells ringing and then an identical failure for Felipe Massa two laps later changed the game. It became about survival and minimising the risk of suffering a tyre failure and potentially not finishing the race.

Many drivers were switched onto the hard tyre, but it was noticeable that both Force India cars , both Williams and Jenson Button went for the mediums. Apart from Di Resta, these drivers were all doing two stop races and clearly didn’t feel as much at risk at this stage.

In the pit garages there was plenty of action; a message was sent to all teams advising them to increase the tyre pressures as a precaution. Ideally the tyres should be run at 19psi, but some teams were running them lower, to increase grip and temperature. But there was a suspicion that this was contributing to the failures, with drivers being aggressive over the kerbs and the high loadings on Silverstone’s many fast corners.

Some observed the advice to increase pressures and stay off the kerbs and some did not.

Engineers were photographing the inside shoulder of the tyres coming off their cars, and comparing them with others to make a judgement on how best to run the tyres. At a time like this, experienced engineers will always revert to what they know, from Free Practice, they can achieve safely and run to that plan.

The strategy for the rest of the race was decided by that. However there was another factor, which came into play and helped to decide the outcome and that was the safety cars.

Safety car a double-edged sword

FIA Race Director Charlie Whiting has said that he came close to stopping the race and some teams were surprised that he didn’t. However he did deploy two safety cars; once to clear debris from a failure and once because Sebastian Vettel’s broken Red Bull car was parked in a dangerous place.

Incidentally, with his team mate Webber making up for lost time after a poor start, Vettel leaving the car where he did and triggering the safety car, which closed up the field, certainly helped Webber to get back into contention. He was 14.5 seconds behind Rosberg at that point. But the safety car allowed him to close up and after the restart to challenge for the win in the final laps.

The problem with deploying safety cars is that F1 cars touring round slowly behind the safety car rapidly lose tyre pressure and temperature, increasing the risk that further failures will occur. Whiting knew that when he deployed them, but he had no choice as there were more dominant safety priorities at the time, which required the safety car’s intervention.

The second safety car really hurt the races of two stoppers Kimi Raikkonen, Adrian Sutil and Daniel Ricciardo. They stayed out on old tyres, while Webber, Rosberg and Alonso came in, so the two stoppers were vulnerable in the closing stages to cars with fresher tyres.

Raikkonen questioned the decision to stay out over the radio and the team has since apologised to him for the mistake. He was running second at the time and could have taken advantage of the opportunity to get a free set of tyres with minimum time penalty, as the other leaders did. He ended up finishing fifth, setting a new record for consecutive points finishes in F1, with 25.

Behind the safety car, the safest thing to do was to bring the driver in and put on a new set of tyres with increased tyre pressures, giving you the best chance to finish the race without incident, even if it might hurt your performance a bit to be running the tyres too firm.

Alonso lucky and unlucky

Fernando Alonso was lucky that the tyre failure he suffered was when he was on his way into the pits, so it did not ruin his race. But he was an interesting case study for the wrong reasons in the closing stages. He was fourth behind Rosberg, Raikkonen and Webber as Vettel pulled off the circuit at the end of lap 41, but already committed to making a pit stop.

He served his stop when the others were at racing speed, then as he came out of the pits the safety car was deployed, so he had to complete the lap at the reduced control speed. Meanwhile his rivals, now ahead of him were able to pit at the end of the lap - losing less time in their pit stop as the field is all travelling at reduced speed - and they came back out ahead of him, along with drivers like Sutil and Ricciardo who had not stopped.

Alonso dropped to eighth and had to be at his very best to fight his way past these cars to finish third and take 15 points out of Vettel’s championship lead.

The UBS Race Strategy Report is written by James Allen with input and data from several F1 team strategists, from Pirelli and from JA on F1 technical adviser Mark Gillan

Race History Graph

Courtesy of Williams F1 Team

NB - The safety car periods (shaded in brown) have been adapted to make the graph easier to view.

Note the pace differential in the final stint between the cars doing two stops, like Raikkonen, Sutil and Ricciardo and the three stoppers. Also note Hamilton's pace; he was two stopping as well!

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