If the last two races at Silverstone have taught us anything, it's that the current breed of Formula One cars are incredibly sensitive machines. From one weekend to the next, we saw the same drivers in the same cars on the same circuit produce two very different results at the front of the field.
The fact the second of those two results saw the previously-dominant Mercedes team struggle and Max Verstappen take his first win of 2020 gives some hope for a more competitive championship this year. But was Sunday's 70th Anniversary Grand Prix simply an outlier in a season of Mercedes dominance or has Red Bull exposed a true weakness in the W11's package?
What changed and why did it impact Mercedes?
The main performance differentiators between cars in Formula One are power and downforce. But no matter how much you have of either, you still need to transfer it to the track through the tyres. If those tyres are not performing as they should do, it doesn't matter how much raw performance your car has in the windtunnel or on the dyno, it won't result in faster lap times.
It's why teams spend so much money and time trying to understand the tyres. Get it right and, at the very least, you will be able to maximise the performance of the car. Get it wrong and hundreds of hours of work back at the factory can come to nothing on race day.
Nothing fundamentally changed in the downforce levels and power outputs of the Red Bull and Mercedes this weekend. Look at qualifying and you'll still see a gap of around a second, which sits at the upper end of the spectrum of gaps to Mercedes we have seen this year. But over the course the race, a clear weakness was exposed on the W11 that meant it was unable to transfer its performance advantage to the track.
The reason was clear from the TV pictures. As Mercedes went deeper into each stint of the race, the surface of its rear tyres was blistering and splitting open. The impact on performance was significant and after just a handful of laps on each set of tyres, Mercedes had to tell its drivers to slow down to preserve their rubber.
It's important to state that this was a very different tyre issue to the one that emerged in such explosive fashion last weekend, when both Mercedes drivers experienced front-left tyre failures. That was down to the physical wear of the tread of the tyre, whereas Sunday's issue was the overheating of that tread.
In terms of race-ending failures, the former is far more worrying but there was never really a fear that Mercedes would suffer a repeat of the failures seen at the British Grand Prix. The blistering, as bad as it looked, didn't damage the integrity of the tyre, just its performance.
Blistering had been a secondary concern last weekend, but on Sunday it became Mercedes' primary weakness.
The reasons for the change from one weekend to the next are three-fold:
1. The tyre compounds were a step softer this week
2. The tyre pressures were higher
3. The track temperatures were several degrees hotter
Using softer compounds at the second race weekend was F1's idea. With two races at the same circuit, the plan was to mix things up for the teams by changing one of the most sensitive variables -- the rubber on which they race. The plan worked perfectly.
The softer compounds were more susceptible to overheating and, on a circuit where the two Mercedes drivers were able to push each other to fastest lap after fastest lap one week ago, they were suddenly in a race in which they were aiming to finish at the slowest, most tyre-friendly speed possible. Blistering had been an issue the previous weekend, but not on the same scale and mainly on the front tyres. But the softer compounds combined with higher temperatures and higher tyre pressures exposed a weakness on the Mercedes.
Pirelli upped the minimum tyre pressures from the previous weekend to protect the tyre from the forces that caused the three failures at the British Grand Prix. The side-effect of inflating the tyres an extra PSI at the rear and two PSI at the front was that it made the tyres slightly more bulbous, reducing the contact patch of the tyre. We are talking about levels that are not noticeable to the human eye, but that doesn't make them any less susceptible to the laws of physics.
A smaller contact patch is subject to more strain and therefore is more susceptible to overheating. That overheating then has a spiralling effect on the loss of performance as the pressure inside the tyre increases as a result, reducing the contact patch further. Eventually the blisters emerge on the surface of the tyre, which, in the case of Mercedes on Sunday, resulted in a loss of performance as the tyre surface started to open up.
Mercedes knew it would be at risk of blistering ahead of the race, but it was expecting it to be worse on the front (as had been the case at the first Silverstone race) than the rear. In attempting to protect the front tyres with its set-up choices, the team seemingly left the rears exposed and when the pit wall saw the temperatures and pressures going through the roof early in the stint, it radioed its drivers to back off.
Yet the tyre compounds, starting pressures and temperatures were the same for Red Bull, so why did it impact Mercedes so much more?
"We knew that blistering was an issue, we knew that last week and we were talking to the drivers this morning and we knew the temperatures at which it would occur, so that wasn't news to us," Mercedes head of trackside engineering Andrew Shovlin said on Sunday evening.
"What was news to us is that we are at the very, very worst end of that problem and Red Bull appear to be at the very, very best end of that spectrum. And that's the thing we need to understand.
"There have been other races when everyone has been in the same boat, but why we were an outlier [on Sunday], right now we haven't got an answer."
The extent of the overheating issue on Mercedes' performance was clear after both drivers pitted for hard tyres on lap 13 and 14. That put them on the same compound as Verstappen, who had started on hards, for the first time in the race, and it was at that point that the Mercedes pit wall started to realise how much harder Verstappen was able to push.
In the opening laps of their stints, the Mercedes drivers went faster than Verstappen, but they could only maintain that pace for two laps before they had to back off to bring temperatures back under control. As Verstappen's times steadily improved to the low 1:31s over the remainder of his opening 26-lap stint , Bottas' and Hamilton's pace dropped to mid 1:32s.
A car that was nearly a second faster in qualifying was now 1.5s slower in the race and it was all down to the way it was treating its tyres.
The result was Verstappen was able to pit for medium tyres on lap 26, come out directly behind Bottas and pass him on track to take the de facto lead of the race. Both drivers then had one pit stop left, which they made on lap 32 for a straight fight to the end that Verstappen easily won. Hamilton stayed out until lap 44, but by that point it had been clear for some time that Mercedes had lost the race to Verstappen.
Did Mercedes get its strategy wrong?
The advantage mentioned above was partly gained by Red Bull starting on the hard tyres -- a decision made on Saturday when Verstappen used that compound to progress from the second part of qualifying to the Q3 pole position shootout. Under F1's rules, the tyres used by the top ten in Q2 become the starting tyres for the race and it meant Red Bull was already ploughing its own furrow with race strategy before the lights went out on Sunday.
Mercedes had pace in reserve to make the same decision in Q2 and start on the hard compound tyre, but it opted not to. With the benefit of hindsight, it seems like a mistake, but the more you look at the relative race pace of the two cars (especially in the stint mentioned above), the more you realise it probably wouldn't have made any difference.
What's more, Mercedes, which on Saturday afternoon still thought it had the faster race car, had its reasons for not starting on the hard tyres.
First off, there was the risk that if they damaged that set of tyres while pushing in qualifying -- with a lock up or from debris (as was the case last weekend) -- they would then have to carry that damaged set of tyres into the race and ask a huge amount of it.
Secondly, by opting to go long with hard tyres in the first stint, they left themselves open to attack from an undercut from Red Bull at the first pit stop, possibly forcing Mercedes off the tyre earlier than they would have liked given their concerns about blistering.
Finally, an early safety car period -- like the one we saw the previous week -- would have been an advantage if they had started on the mediums as they could get rid of the less suitable race tyre by pitting under the caution period with a relatively cheap pit stop. By contrast, it would be a disadvantage if they started on the hard tyres as they would have been tempted to change off the better race tyre earlier than they would have liked.
But above all else, the pace of the Red Bull meant starting on the hard tyre wouldn't have made much difference to the eventual outcome of the race.
"There were times in the race that Max was 1.5s quicker than us because we were having to limp around and keep the temperatures down on the tyre," Shovlin explained after the race. "When you've got that kind of difference, we can't defend against them by being on the same tyre as them.
"We might have got through the first stint OK, but we wouldn't have been able to go long like they did. As soon as they closed up on us, they would have been forcing us into an early stop and they would have still extended.
"So we were still pretty happy with that decision to start on that tyre, but equally I think it made perfect sense for Red Bull to go with the hard if they are coming from behind. It meant they could offset on strategy and it opened up those avenues that you saw them take advantage of today.
"The magnitude of our problem is such that the result would always be the same."
The decision to pit Bottas on the same lap as Verstappen also seemed like a strange one, and effectively conceded defeat to Red Bull. Bottas was critical of the team after the race, but the timing of his stop was not so much about challenging Verstappen as it was defending from Charles Leclerc, who was emerging as a threat on a one-stop strategy.
What's more, the overriding factor for pitting Bottas when the team did was a concern about vibrations from his destroyed rear tyres. Hamilton was not suffering the same vibrations, allowing him to go further before stopping, but both that strategy, which proved superior to Bottas', and the potential for an audacious one-stop with Hamilton would not be enough to beat Verstappen regardless.
"His tyres were doing better towards the end of that stint and were running a bit cooler but then he started to suffer a drop in performance," Shovlin explained. "The problem is that if you then try to make that one-stop work and it doesn't, you then have to come in and it wouldn't have given him any time to attack Leclerc.
"We could see Verstappen would get us anyway, there was a high likelihood that we were going to have to pit anyway and you are better to accept that and commit to it than end up with a failed one-stop."
What does it mean for the championship?
We finally saw a race that the mighty Mercedes W11 couldn't win. Verstappen should take full credit for putting Mercedes in a difficult position and Red Bull should also be congratulated for finding a set-up that kept his tyres in top condition despite the unusual circumstances of softer compounds, higher pressures and higher temperatures.
The reward was 25 points, narrowing Verstappen's gap to Hamilton the championship to 30 points and overtaking Bottas in the standings for second place. Considering Verstappen saw a likely podium finish go missing with an engine failure at the first round in Austria and missed out on a 14-point swing over Hamilton when he made an unnecessary pit stop at the British Grand Prix, the championship picture could have been even closer at this stage of the season.
But that shouldn't distract from the overwhelming evidence that in normal conditions this season Mercedes has still been dominant. The 70th Anniversary Grand Prix was an outlier in terms of race conditions and it was the only race where Mercedes truly looked vulnerable in terms of performance.What's more, the fact Verstappen could have been within 10 points of Hamilton had Red Bull maximised all its opportunities is of little significance if Mercedes rock up at the next round and dominate from the front once more.
Which leads us to the big question: Will the hotter temperatures forecast next week in Barcelona expose Mercedes' weaknesses again at the Spanish Grand Prix?
The tyre compounds are set to go a step harder and the tyre pressures are returning to relatively normal levels (4 PSI lower than Sunday at the front and 1.5 PSI lower at the rear). But the Mercedes engineering team led by Shovlin knows it cannot rely on those factors to avoid a repeat when the third factor, the hot ambient temperature, is set to sky rocket.
"What we need to do is get up tomorrow and be really excited about fixing the issue," Shovlin said on Sunday night. "There is an element of urgency here, because we are flying out to Barcelona on Tuesday, running in practice on Friday and the forecast is 34C for the weekend.
"The [Barcelona] track is high-energy, like Silverstone, and so we are well aware that, if we don't get on top of it, we will have another Sunday of looking silly.
"But while the racing is great fun, the engineering is great fun as well, and there are quite a few of us who welcome these challenges as engineers because it is a real test of your mettle."
Asked if running on the harder compounds (C1, C2 and C3 will be available in Barcelona instead of C2, C3 and C4 at the second Silverstone race), Shovlin added: "If we don't solve the issue, we can probably hide from it a little bit on that C1 tyre, but we have still got to run the tyre [the C2] that was causing us grief today.
"You've seen that Red Bull are not that far off us when we are looking at our best, so I think to be honest, if we don't make progress we will be in trouble there as well. That's where this urgency to get a bit of a grip on it comes from."
On the face of it, the 70th Anniversary Grand Prix and the Red Bull victory that came with it looks like the exception rather than the rule for the rest of the season. But if Mercedes struggles again this weekend and Verstappen takes a second consecutive victory, it could just give Red Bull the sniff it needs to mount a serious championship challenge.