2011 Formula One Pirelli Tyre Analysis

This thread has so far provided detailed coverage of the first five races. In a nineteen race season, that could make for one very long piece indeed, but actually most of the story about how tyres affected the races is now told. Monaco though is worth telling because it marked the turning point in how teams worked with the soft tyre.

Monaco is always a bit of an odd-ball for all the right reasons. It served up what we thought was another odd-ball when Vettel went 56 laps on the yellow tyre.

Monaco Grand Prix
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The supersofts made their long awaited debut. You have to say, they look great, they look superfast - they promised to be like qualifying tyres that were superquick for one lap before dying rapidly. That’s not really what happened, was it? They did add to a spectacular race: they were quick, as Button in particular found, but so too were the yellow tyres and the yellow ones lasted longer. Much longer.

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If you remember the Monaco Grand Prix, we ended with a lot of ifs, buts and maybes as a red flag allowed Vettel a free tyre change to Alonso and Button’s detriment. Vettel was on his yellow, prime tyres because of a mix up in the pits at his first stop and when the lap 34 safety car came out and other pitted, he stayed out inherited the lead.

Remember the scaled axis on the chart, where 60 laps is a standard race. Monaco is more laps, so Vettel's 56 laps there is equivalent to 43 laps on this chart. The last clean data point we have for Vettel's stint is his 52nd because the 53rd - 56th were under affacted by yellows and the safety car. Conveniently 52/78 = 40/60, so is shown as lap 40 here and Vettel was bang on it that lap. You can also see the gap in Vettel's plotted times from 14 to 17 when the earlier safety car was out.

Vettel knew that if he stopped, he could do no better than 3rd. He figured that by staying out he could do no worse than that, so he gave it a go. If you look closely at the dots, there seems to be more of a wave to Vettel's pattern than the polynomial that excel has plotted. How much the safety car after the first part of the stint helped is also unclear but each slower lap is followed by a sequence of faster ones, so perhaps Sebastian found a way to cool the tyres off for a lap while minimising the time lost?

Petrov and even Kovaleinen's Lotus also seem to have made their yellow tyres last. Button spent very little time on the softs, but was extremely quick when he did fit them.
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Vettel had led the race but was behind Button when the first safety car came out. Jenson had used the undercut to get past at the first stop and then chose an aggressive three stop approach. Button had the pace that day as the chart shows, but was unable to overtake after the safety car went in and had to stop again anyway to fit the prime tyres. In doing so, Alonso also nipped past him as they both chased down Vettel.

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Alonso seems to have had a wild time on the supersofts (the curve shape is repeated in later races where the tyre is used) but he fitted the prime tyres when Jenson was losing time behind Vettel and that undercut allowed Alonso into second when it was all said and done. Button was fastest, but he came third…

During the race, the commentators and even Button’s race engineer speculated about Vettel reaching the cliff. He didn’t, but whether that is because of the red flag, we will never know. The data does show that his tyres were getting worse, but they would also come back after a seemingly slow lap.

Furthermore, it seems that Alonso's tyres were not in any better shape than Vettel's, so Added to the difficulty overtaking, would Alonso or Button have been able to use a 1s advantage to get past? Button hadn’t been able to earlier in the race, so perhaps not?
 
A Good Time to Stop?
When was the right time to stop in 2011...?

The chart below shows how strategies compared theoretically

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Within this is a further layer of complexity. How far do you go on each tyre (in the standard 200 mile, 60 lap race that is being shown in this thread)? The optimum answer based on the average degradation on each tyre works out as this.

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