Not too hot, not too cold: Why do tyre temperatures decide races?
Ferrari's Fernando Alonso hopes for warmer weather at the Hungarian Grand Prix while McLaren thrive in chillier climes
Fernando Alonso came to Hungary pinning his hopes of victory on a change in the weather.
"At the Hungaroring it should be more in keeping with summer, which is no bad thing as I've had enough of the cold and damp we experienced in England and Germany," he said. "That goes not just for me, but also for our car: it would definitely work better in temperatures higher than the 13 degrees we had last Sunday."
But why does the ambient temperature exert such a crucial influence on the performance of an F1 car?
The standing joke in F1 is that tyres are round, black and boring. They aren't. A decent set can give you a performance hike that you'd need another 250 bhp of power from the engine to achieve. But when you have a sole supplier, in F1's case Pirelli, who took over from Bridgestone at the start of the season, everyone is on the same rubber and it comes down to who best manages the highly complex interaction between rubber and road.
Pirelli have four different tread compounds, and they are differentiated by stiffness and their optimal temperature range. Their medium compound is six per cent softer than the hard; the soft compound is 16 per cent softer than the hard; and the supersoft 27 per cent softer than the hard. Generally speaking, the supersoft compound is the grippiest but least durable, so trading off performance for longevity is part of a race strategist's job. Pirelli gives teams two compounds per race, depending on the characteristics of the circuit.
The stiffness and grip of a tyre tends to decrease with temperature, so if a compound is working far off its optimal temperature range, it loses grip. It takes the tyres too long to warm up and the car will slide around.
Sometimes one driver's style can warm the tyres faster than another's.
Fernando Alonso makes coarser steering inputs in corners than team-mate Felipe Massa, and often has an advantage over him as a result, because his tyres operate in their intended temperature range even when it is cool. Jenson Button, like Massa, suffered badly in comparison with Rubens Barrichello when they were team-mates at Brawn in his championship year. When temperatures were low, as they were at the Nurburgring last week, with track and ambient highs of only 13C, the smooth drivers suffered.
Working outside a tyre's optimal temperature range always brings more rapid wear, too. The capability of keeping the tyre in the correct temperature window is part of a driver's art.
The characteristics of each car also exert a major influence, however. The Ferrari is easy on its tyres this year, which is beneficial in terms of going longer on a given set during races but detrimental insofar as the car does not work as well in cooler conditions.
The McLaren, meanwhile, has tended to do well because, according to Button, the design of its wheels does not disperse heat as much as some others. This is good in cool conditions because it keeps the tyres nice and warm, but in hotter temperatures it can be a problem.
The Red Bull, like Goldilocks's last sample of porridge, has thus far tended to be just right. This is not only because it has greater downforce than either the McLaren or the Ferrari, but because all of the other little factors, particularly weight distribution, seem to be just about spot-on.
Even so, Sebastian Vettel has been able to get more out of his Pirellis this year than team-mate Mark Webber, which is part of the reason why the German made hay while the sun shone in the early races and has such a big championship points lead.
Yesterday's Practice Times
First Practice: 1 L Hamilton (GB) McLaren-Mercedes 1min 23.350secs; 2 S Vettel (Ger) Red Bull-Renault 1:23.564; 3 F Alonso (Sp) Ferrari 1:23.642; 4 M Webber (Aus) Red Bull-Renault 1:23.666; 5 J Button (GB) McLaren-Mercedes 1:23.772; 6 F Massa (Br) Ferrari 1:24.115; 7 N Rosberg (Ger) Mercedes GP 1:24.250; 8 M Schumacher (Ger) Mercedes GP 1:24.369; 9 S Perez (Mex) Sauber 1:24.620; 10 V Petrov (Rus) Renault 1:25.093; 11 K Kobayashi (Japan) Sauber 1:25.113; 12 P Di Resta (GB) Force India-Mercedes 1:25.336; 13 N Hulkenberg (Ger) Force India-Mercedes 1:25.357; 14 R Barrichello (Br) Williams-Cosworth 1:25.836; 15 B Senna (Br) Renault 1:25.855; 16 S Buemi (Swit) Toro Rosso-Ferrari 1:25.890; 17 J Alguersuari (Sp) Toro Rosso-Ferrari 1:26.099; 18 P Maldonado (Ven) Williams-Cosworth 1:26.124; 19 H Kovalainen (Fin) Lotus-Renault 1:26.878; 20 J Trulli (It) Lotus-Renault 1:27.352; 21 T Glock (Ger) Virgin-Cosworth 1:28.533; 22 J d'Ambrosio (Bel) Virgin-Cosworth 1:28.903; 23 V Liuzzi (It) Hispania-Cosworth 1:29.059; 24 D Ricciardo (Aus) Hispania-Cosworth 1:29.904. Second Practice: 1 L Hamilton 1min 21.018secs; 2 F Alonso 1:21.259; 3 J Button 1:21.322; 4 M Webber 1:21.508; 5 S Vettel 1:21.549; 6 F Massa 1:22.099; 7 N Rosberg 1:22.121; 8 M Schumacher 1:22.440; 9 P Di Resta 1:22.835; 10 A Sutil (Ger) Force India-Mercedes 1:22.981; 11 K Kobayashi 1:23.030; 12 S Perez 1:23.399; 13 R Barrichello 1:23.679; 14 N Heidfeld (Ger) Renault 1:23.861; 15 P Maldonado 1:24.181; 16 J Alguersuari 1:24.182; 17 V Petrov 1:24.546; 18 S Buemi 1:24.878; 19 J Trulli 1:24.994; 20 H Kovalainen 1:25.447; 21 T Glock 1:26.823; 22 J d'Ambrosio 1:27.261; 23 D Ricciardo 1:27.730; 24 V Liuzzi 1:28.255.
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