How Hamilton found the decisive six tenths

Six tenths of a second. It's a long time in motorsport, but think about how long it really is. This was the margin - 0.636 seconds to be precise - that separated Lewis Hamilton from Nico Rosberg at the end of the Spanish Grand Prix. Next to nothing.

Those two thirds of a second mean that Rosberg no longer leads the world championship, with the pendulum swinging ominously towards Hamilton thanks to four consecutive wins. It means the world to Hamilton, or at least it will if he's still ahead after 14 more races.

But as a measurement of time to human perception, it's not much more than the blink of an eye. So where did those six tenths come from?

This was another weekend when the other 20 cars faded into the background. They were once again the B-feature but, to the credit of Hamilton and Rosberg, even with just the two Silver Arrows on track this grand prix would have held the attention.

It was an old-school strategic battle that tested the two drivers to their limits in ways not obvious to the naked eye. It wasn't the wheel-to-wheel thrill ride provided by the pair in Bahrain, but it was a different kind of spectacle.

Bahrain was the big-budget action blockbuster, Spain the immersive psychological thriller. Less popular appeal, certainly, but one that delighted the connoisseur all the more for its relative rarity in this era of F1.

Hamilton looked unstoppable on Friday © LAT

The first act, on Friday, gave us a hint of what was to come. While Hamilton's advantage on the timesheets was just over 0.4s, he had an even bigger margin over Rosberg on long-run pace. Crunch the numbers and there was that fraction again: six tenths per lap.

Over a race distance, that would add up to a lead of 40 seconds, so clearly something changed overnight.

There were reasons for Rosberg struggling relative to Hamilton. On Friday morning an ERS problem had restricted him to nine laps, and the car was not at all to his liking come the afternoon session. But Rosberg turned the tables.

"I wasn't feeling comfortable and yes, in the morning I missed out on one run, which just knocks me back a bit," said Rosberg on Saturday. "There was a little bit of catching up to do from then on because I wasn't able to get the car right by the end of Friday."

In 24 hours, Hamilton had gone from dead cert for pole position, fastest lap and the world championship to playing catch-up. His car was not faster in qualifying and Rosberg had the edge through Q1 and Q2, but Hamilton dug deep, hung it all out and pocketed pole. You could argue that his quietly spectacular lap, 0.168s faster than Rosberg's, was where those magic six tenths really came from. After all, once he had the lead at the start, the race was in his control.

But was it really a virtuoso qualifying performance that earned Hamilton that cushion? Perhaps it was really Rosberg's disappointing start. After all, with a 730-metre blast to the apex of Turn 1 (the longest on the calendar), the German had every chance of seizing the initiative on the first lap. He reckoned he had the edge on pace, so once up front the race would be his.

Unfortunately, getting a good start in an F1 car is not as easy as some would have you believe. Relying on a multitude of factors - the quality of the practice start, the right clutch settings, tyre temperature, the precise operation of the clutch paddles - there's a lot to get right and wrong. Rosberg has been getting more wrong of late, while Hamilton has been on the money. The clutch operation appears to be the problem.

Hamilton made a clean break at the lights © LAT

"The start unfortunately was poor," said Rosberg. "It's a bit of a weakness that we have at the moment, just inconsistent, and now I've had a couple of bad starts in a row that's costly. Always losing at the start, that's not good. We need to work on that."

On the plus side he was still second. Just as in Bahrain, whichever driver was behind was always likely to switch to the alternative strategy. Hamilton stuck with the orthodox medium/medium/hard strategy and Rosberg, knowing he would switch to hards, sat two seconds back from his team-mate in the hope that his first stint would be better.

Sure enough, Rosberg's confidence in his car set-up was well placed. He and his crew knew that there was a way to seize back all the ground he had lost, plus the crucial six tenths advantage.

Just as in Bahrain, his tyres held up slightly better in the first stint. He ran three laps longer than Hamilton to offset his strategy and hopefully gain an advantage later on. And this throws up some more numbers. Rosberg was 1.635s behind Hamilton when the leader pitted.

Once the pitstop cycle was complete, he was 3.757s behind. In the context of the six tenths, that's a huge amount of time. It was a reasonable trade-off, and that was mitigated by the fact that Hamilton lost a second or so with a slow stop (although only seven tenths in the pitlane as a whole).

This was the key stint of the race. Rosberg needed to get himself to within two seconds of Hamilton, which would open up the possibility of stopping a lap early and undercutting him. Hamilton simply needed to keep Rosberg around four seconds back.

It was a tense stint as the gap ebbed and flowed. But the net result was that Hamilton managed to deliver the goods. At the start of the 42nd lap, on which he dived into the pits for a set of the slower hard-compound Pirellis, Hamilton's advantage was 3.898s.

That's a net gain of 0.141s over 20 of the most-tense laps of the season. Doesn't sound like much, but in the chase for those crucial six tenths every little helps.

With overtaking on-track looking impossible, Rosberg sought a strategy advantage © LAT

Rosberg seemed destined to pit on the following lap, but in fact he stayed out a lap beyond that. It was perhaps a move borne of conservatism but all it did was allow Hamilton to pick up a little more time on his fresh rubber. When Rosberg did pit, it was inevitable that he would lose the lead, even though he was stopped for 1.3s less than Hamilton.

That time might have come in handy for Rosberg in the chase for the magical six tenths had he been a bit closer, but by now it was clear that gaining track position strategically was an impossibility. He needed to do what he had failed to do in Bahrain; overtake Hamilton.

The equation was simple. With 20 laps to go, Rosberg trailed Hamilton by 4.856s. He had the faster medium tyres on, which gave him an advantage, and his rubber was also two laps fresher. The chase was on.

Lap 46 +4.856s
Lap 47 +4.658s
Lap 48 +3.682s
Lap 49 +3.716s
Lap 50 +3.149s
Lap 51 +2.359s
Lap 52 +2.067s
Lap 53 +2.796s
Lap 54 +2.773s
Lap 55 +2.628s
Lap 56 +2.196s
Lap 57 +1.871s
Lap 58 +1.460s
Lap 59 +0.984s

With seven laps remaining, Rosberg crossed the line just within the one-second margin he needed to get use his DRS. But Hamilton responded brilliantly and picked up the pace for a few laps.

Lap 60 +1.322s
Lap 61 +1.264s
Lap 62 +1.102s
Lap 63 +0.940s

By doing so, he delayed the endgame by four laps. Now things were getting serious. Hamilton, who complained of front-tyre graining and understeer during the final stint, locked up at the end of the back straight on lap 64 with Rosberg now right behind him.

Rosberg hunts down Hamilton in the closing laps © XPB

Rosberg pushed as hard as he could, having his own lock-up at the end of the back straight on the last lap, a point where he said after the race he could have attempted a "kamikaze move", but even with the DRS he couldn't mount a credible attack. Hamilton weaved his way across the line in jubilation. The timing screen updated the gap: 0.636s.

Hamilton had absorbed the pressure brilliantly. Just as in Bahrain, he had been a little behind in terms of pace, but he'd turned that into victory. In Bahrain, it was with some superb, and sometimes forceful, defending. Here, it was with a combination of stunning qualifying speed and mental fortitude under pressure, with only the occasional chippy radio message suggesting he was feeling anything.

He had struggled for car balance during the race and wanted the front wing eased back for the final stint. But with rubber debris also being cleared, Mercedes had to take a punt on how much to ease it off. Again, it's about fine margins, for Hamilton did struggle in the final stint with that lack of front-end grip, but he still had the car under him to win.

"I wasn't fast enough really today," he admitted after the race. "Nico was quicker.

"Those last laps, there was a huge amount of pressure and he was very, very close to taking it. I don't like that, being in that position. I like to say it was no problem and under control - but it wasn't!"

Now, remember the decision to run two laps longer at the end of the second stint, which cost Rosberg a little time to Hamilton? Well, in the context of what Rosberg said after the race, specifically that with "one more lap I could have given it a good go", you could argue that this was where that sixth tenths margin was really established by Hamilton.

But realistically, could Rosberg really be expected to pull off a pass on his team-mate with an extra lap or even two? Probably not, although Hamilton would certainly have been forced to defend.

So how do we account for those six tenths and balance the books? Here are the ingredients: a Friday-morning ERS problem, a change in track conditions, one car improving on Saturday and one getting worse, a virtuoso qualifying lap, a poor start, running one lap longer in the second stint, a couple of slow pitstops, and 66 laps.

Ricciardo was in a different race in third place © XPB

Those elements, plus thousands more, all played their part in what added up to a marginal win for Hamilton. He was the one who negotiated all the pitfalls and kept Rosberg at arm's length when required, and the reward was arguably an even better victory than the one in Bahrain.

Was there ever a better illustration of how infinitesimal the margins in grand prix racing can be? Perhaps not, given that if you looked at what might be called 'Class B', there was a whole other race going on populated by 20 other cars that Hamilton and Rosberg only encountered while lapping.

Daniel Ricciardo finished a massive 49 seconds behind this victory battle, albeit after losing time in the first stint bottled up behind the Williams of Valtteri Bottas. At a track where even the Mercedes drivers suggested the gap might be reduced, this was a stunning demonstration of the supremacy of the Silver Arrows.

Only six cars finished on the lead lap, the others being Sebastian Vettel's Red Bull, which surged through from 15th on the grid to fourth after committing early to a three-stop strategy, and Fernando Alonso's Ferrari.

But this race was really all about the two Mercedes. After the race, Rosberg made very clear where he believes Hamilton found that 0.636s.

"The race was really lost in qualifying and at the start," he said. "Those were the two opportunities I had. Qualifying was very, very close and I even had a bit of a problem which we found in hindsight where I was a little bit down on power on the straight. But the difference was not enough to get pole.

"Then I just had a poor start, so those were the two shots that I had at it and it didn't work out. In the race, I nearly got another opportunity at the very end, but again just not enough. One more lap and I could have given it a go.

"But I would have done the same again at the start of the weekend. Of course, I also missed FP1, which didn't help either.

"Many small things add up, and there are only very small gaps. So next time..."