Nico Rosberg celebrates in ChinaNico Rosberg took a dominant victory in China as Mercedes hit the sweet spot of tyre management — but after winning with plenty in reserve does it suggest the team is really about to hit the big time?
Tyre management was key to Rosberg's victory in Shanghai, as it will be key to the entire season of racing, with Pirelli's new rubber appearing to have a narrow working window with some of the front-running cars.
This operating window is affected significantly by ambient temperature at the circuit and by the resultant track surface temperature.
In the season-opening race in Melbourne Mercedes overheated its tyres; in Malaysia it struggled to get them up to temperature; in China, in temperatures of around 22 degrees, it got it just right.
The swing in data between Melbourne and Malaysia was instrumental to Mercedes' victory in China, as it gave them the ability to learn how their car works its tyres at both ends of the scale, and more importantly why it was not performing in the first two races.
Rosberg made it look easy on Sunday because, pretty much undeniably, it was. His race came straight out of the classic Vettel mould.
By starting out in front and holding the lead into the first corner, Rosberg was able to steadily drop his team-mate Schumacher behind, with Button sitting frustrated just a second behind the second Mercedes but unable to pass.
By the time Button pitted on lap 11 he was already 6.8s behind having been averaging around the 1:44.2s mark compared to Rosberg's 1:43.7s for most of the run. After that stop, however, Button came out in clean air and, making the most of fresh soft tyres, he was lapping briefly around 1m42.6s, a second faster than Rosberg. After two further laps, when Rosberg made his first stop, Button had reduced the gap to 3.5s.
In the next stint, once the other runners were out of the way, the pair were surprisingly evenly matched given that Rosberg was on the medium tyre and Button on the soft. With both in clean air, in fact, Rosberg, who was now on a two-stop strategy, was marginally faster and the gap had stretched to 4.3s by the time Button made his second stop of three, on lap 24.
But that's where Button's 3-stop strategy fell into trouble.
Button dropped back into the pack, coming out on medium tyres in ninth place. He quickly passed Senna but spent two laps behind Perez then got stuck behind Vettel for two laps and Grosjean for one. By the time he'd worked his way back up to second, seven laps after his stop, he was now some 14.5s behind Rosberg.
Once he was finally clear, however, Button showed what he could have been doing in clean air. He put in a very rapid lap of 1m40.9s and was then lapping a full two seconds faster than Rosberg, who had been averaging around 1m43s laps in that period and was by this point nursing a set of mediums that were 18 laps old.
When Rosberg made his second and final stop he dropped to 9.5s behind Button but the Briton still had another stop to go and the gap was 7.5s when he pitted on lap 39.
If Button had been able to run at his clean-air pace for his entire third stint, his advantage could have been around 21.5s — which would have made things very close indeed.
After that stint, then, Button's final pitstop disaster didn't really count for much.
The problem that caused him to be held stationary in his pit for an extra six seconds did affect his final stint significantly — because it put him behind the slower paced cars of Raikkonen and Vettel. But even if it had gone right, he would still have been 14s behind Rosberg with 16 laps to go — and although Button did have a slight speed advantage by the end, it was certainly nowhere near a second per lap — and Rosberg admitted after the race he was in conservation mode, so could have pushed harder had he needed to.
There was one final piece of the equation, however, and that was the tyre cliff - as demonstrated by Kimi Raikkonen's rapid fall when he went from second to 12th in two laps.
The tyres degrade relatively smoothly but they do have a tread limit and when that is reached it is like driving on ice. Raikkonen's tyres went on lap 48, at which point they were 20 laps old. Rosberg's had to last 22 laps to get to the finish — but with careful tyre management he made it work.
Mercedes proved in China, then, that they do now genuinely have the pace to win - but only in those kinds of temperatures.
Team boss Ross Brawn, however, suggested confidently that the analysis done since Melbourne has given them an understanding of what to do with the car and tyres over the whole range.
Bahrain will offer a new temperature extreme — so for this weekend it's another trip into the unknown — but with the temperatures in China likely to be similar to many races we see this year, last weekend will certainly have given Mercedes confidence for the long-run...