Why inflation left Mercedes poorer at Silverstone

"They're balloons now," said Lewis Hamilton of his Pirelli tyres post-70th Anniversary Grand Prix. "They're the highest pressures we've ever had on a track like that. I wouldn't be surprised if that was a thing for us, but I don't know if anyone else struggled with blistering like we had so it's something we'll look into."

And it's true. Between weekends, and perhaps in response to the softer grade of tyres being run and the trio of blow-outs last time out, the tyres had swelled up thanks to a change in the mandated tyre pressures.

For Silverstone's first race, Pirelli mandated a minimum pressure of 25psi at the front (approximately 1.7 bar), and 21psi at the rear - and for the second, those pressures were pumped up to 27psi and 22psi at the front and rear respectively. That's quite a lot of extra inflation in the mix, especially when you consider that last year's tyres were allowed to be about 23psi and 20.5psi front-to-back.

There are several reasons for the dramatic climb in pressures, one of those a legacy of last year's Abu Dhabi tyre tests. Then, Pirelli threw a new construction of tyre at the teams - with a squarer profile - which would be able to accept the larger aerodynamic loading placed upon them thanks to F1's irrepressible development between seasons.

But the teams, having largely settled on aero configurations for the 2020 cars which would be affected by the change in shape, vetoed them. Pirelli was forced instead to raise the mandatory pressures on the old construction in response.

For softer rubber, low pressures mean that the tyres can generate more heat as they are able to deform more easily under load. The energy put through the elastomers that the tyre is made of means that it they can stretch, and expend that used energy as heat.

You'll notice that, if you stretch a rubber band repetitively, it begins to get warmer and warmer - and that effect is the same for tyre rubber as it moves around. But over the course of the race distance, this also vastly inflates (if you'll pardon the pun) the amount of wear that the tyres experience. To safeguard against that, raising tyre pressure reduces the amount of movement in the tyre carcass and protects it from thermally degrading.

With the addition of heat, those gas particles now have more motion thanks to their extra energy, and thus raise the internal pressure even further

That's the first sciency bit out of the way, but Chapter Two of Tyre Physics 101 is one more pertinent to Hamilton's balloon allegory. By increasing the pressures when the tyres are cold through pumping more air into it, there are now more gas particles - teams use nitrogen due to its lower reactivity and greater consistency compared to air - within the tyre.

With the addition of heat, those gas particles now have more motion thanks to their extra energy, and thus raise the internal pressure even further. If the pressure gets too high, then the tyre is going to be a lot harder to get grip out of thanks to the resulting reduction in contact patch.

Comparing the Mercedes and Red Bull cars, it's abundantly clear which car has the most downforce. Indeed, the Mercedes ran with a higher-downforce rear wing at Silverstone, because it knows that the advantage that its power unit possesses over the rest of the field on the straights will nullify the drag caveat.

But in hotter climes, the surplus of downforce paired with the high-energy right-handers at Silverstone jacks the pressures up even further, inflating the tyre far more than the leaner-running Red Bull did. And with the hotter temperatures to boot, that also opened the door to blistering.

PLUS: Why Silverstone is "not friends" with tyres

In qualifying trim, that hands Mercedes a colossal advantage over Red Bull. Bottas' pole time of 1m25.154s was over a second faster than Verstappen's best from Q3, hinting at a Mercedes rout on Sunday. But Mercedes immediately had to manage tyre temperatures to keep the temperatures and pressures within a certain window, Bottas being told it was "critical" on just lap six of Silverstone's second race.

Verstappen's Red Bull, however, is putting less load on the tyres overall. The Honda engine, although vastly improved over the iteration that spluttered its way to myriad retirements in McLarens, doesn't have the legs over the Mercedes on the straights. To counteract that, the rear wing was trimmed out a bit to maximise the performance of the RB16 on the quicker bits. In the higher-load corners, the left-hand tyres aren't facing the massacre that Mercedes' tyres did - and Verstappen sounded incredibly chipper deep into a hard-compound stint.

Hence, Hamilton's comments about pressure over the radio. When the six-time champion suggested that Red Bull was running with a lower level of pressure, it wasn't a slanted barb at a team from whom he suspected foul play. Instead, he'd recognised on the fly that the Red Bull's tyres were operating within a more tyre-kind temperature window that wasn't causing the pressures within to rise too far.

On the W11s, the sheer downforce that the car is capable of generating was arguably hurting its chances the most, and the increase in inflation was putting the tyres through something of an assault course. The fact that Hamilton was able to keep going on his second set of tyres and continue to set a consistent pace just a tenth or two down on Verstappen is testament to his tyre management skills, but it could not draw the team's gaze away from the barrel of Verstappen's smoking gun.

PLUS: How ruthless Verstappen exploited Mercedes' Silverstone strength-turned-weakness

"We have seen in the past that the hot conditions somehow don't suit our car," said Mercedes team principal Toto Wolff. "[But] it's much more complex than that. We have probably the quickest package, but the quickest package also involves the most downforce, and the most downforce works the tyres hardest. In that respect, we have to learn how to tune the car to help the tyres survive a little bit."

Wolff explained that the team was able to understand the limits of the Pirelli tyres during the race, having examined a set of Bottas' discarded hard tyres and determined that there was still life left in them.

"Obviously Valtteri's not in a happy place that he was P2 and Lewis was P3," he said. "But it was the learning that happened on-track when we got Valtteri's tyre in. We saw there was actually a lot of rubber left, and we extended Lewis's stint, albeit that there were big vibrations but a lot of rubber.

"Therefore, he was getting quicker and quicker, the more the rubber went down, and that is why we could extend the stint, and eventually Lewis overtook Valtteri."

Mercedes could, arguably, have pushed through the tough middle stint to keep Bottas on the road longer - but of course, hindsight is a wonderful thing.

What Mercedes has is a possible chance at retribution for its 70th Anniversary GP failings. Armed with that knowledge, and following the customary post-race inquest, the team may be afforded another bite at the cherry heading into the upcoming Barcelona round. Anyone lucky enough to grace the Spanish coastlines during August will surely have experienced the sweltering conditions on offer, and the shift of the Barcelona round to high-summer will throw up presumably similar temperatures.

The tyres will be a grade harder for the Spanish Grand Prix, with the C1 offering its services once more as the hard compound, but the lessons that Mercedes now has in its memory bank would help to quell a similar situation.

Like Copse, Abbey and Stowe at Silverstone, Barcelona has Turn 3 and Turn 8 as high-speed right-hand corners that could similarly trip Mercedes up if complacency sets in

"What we need to do is get up tomorrow all excited about getting our heads together and fixing it," says Mercedes' trackside engineering director Andrew Shovlin, "because actually they're really interesting and good, fun problems when you can get on top of them.

"There's an element of urgency here because we're in Barcelona, we're flying out there on Tuesday, running on Friday, it's forecast to be 30 degrees C, the track will be a bit like this. It's a high energy circuit. We're well aware that if we didn't get on top of it, we've got another Sunday of looking silly."

Like Copse, Abbey and Stowe at Silverstone, Barcelona has Turn 3 and Turn 8 as high-speed right-hand corners that could similarly trip Mercedes up if complacency sets in. As for Red Bull, it should be a circuit that will hand the team another opportunity to perform on race day, even if qualifying on pole is beyond its grasp.

But whichever way you cut it, expect Verstappen and Christian Horner to be indulging in some kind of sun-dance ahead of the race at Barcelona.