Explained: Why Mercedes tyre-out in the heat with Spain the next test
Sky F1's Mark Hughes analyses Mercedes' tyre and heat struggles after 2020's early leaders hit big problems at Silverstone; Can Verstappen and Red Bull pounce again at Spanish GP this weekend?
Last Updated: 13/08/20 3:33pm
Pirelli are making no attempt at under-playing the demands upon the tyres at a very hot Barcelona this weekend.
"The expected high temperatures in Barcelona in mid-August will increase thermal degradation on a track already well-known for being tough on tyres, so it's going to be particularly important to manage them and control any overheating that affects traction," said tyre chief Mario Isola.
"Free practice will be crucial to accurately establishing tyre behaviour under these challenging circumstances. With the current cars being faster than ever - as Silverstone recently confirmed - and the Spanish Grand Prix never being run in August before, this should be the most demanding race for tyres we've seen at the Circuit de Catalunya."
While Mercedes' trackside engineering chief Andy Shovlin is wary of the challenge that faces his team in this weekend's Spanish Grand Prix following its tyre blistering-induced defeat by a brilliant Max Verstappen last Sunday.
"We're well aware that if we don't get on top of it, we've got another Sunday of looking silly."
Mercedes were the only team suffering the blistering issue at the Silverstone 70th Anniversary race to anything like this extent (though Nico Hulkenberg was forced into an unplanned third stop in his Racing Point when a blister suddenly opened up on a rear tyre).
The team has only a few days to get a fuller understanding of the problem as we head to a track where the corners are long and quite fast and don't get much of a chance to cool down before the tight twists of the final sector. The forecasted temperature mid-August in Barcelona is comparably high to Silverstone, possibly higher.
Pirelli is bringing the hardest three tyres of its range (C1, 2 and 3), so a step harder than Sunday's race. But Mercedes was suffering its blistering on both the C3 and C2 tyres at Silverstone (and didn't use the C4).
The minimum pressures imposed by Pirelli have been reduced (to a still-high 23psi front/20.5 rear) and the front camber wheel adjustment has been limited less severely. The track itself does not impose quite as much load on the tyres as Silverstone and the optimum downforce levels for lap time are greater than at Silverstone. Whether this latter is a helpful or unhelpful factor for Mercedes depends upon what the root cause of the blistering was.
More downforce will look after the surface of the tyre better as it will be sliding less. But the greater loads created by more downforce impose more strain upon the tyre's core. Blistering occurs when the surface becomes overheated but the root cause of that can be from the core. If the core becomes too hot, it can no longer support the tread as effectively, the grip reduces, the tyres slide, the surface overheats.
Mercedes will be working with Pirelli in trying to understand whether its blistering was caused by a straightforward overheating of the surface or arising from within the core. Given that the Mercedes W11 seems to be endowed with more downforce than any other car, there is a viable working theory that the Silverstone problem has originated within the core.
If Mercedes believes that to be the case, it may opt to run with a less than optimum wing level for the track. Doing this would lose it potential single lap pace, but it may consider this a worthwhile trade-off for keeping the blistering at bay on Sunday.
"We knew blistering was an issue last week," said Shovlin. "We know the sort of temperatures that it will occur at. So [the problem] wasn't news to us. What was news to us was we're at the very worst end of that problem, and Red Bull appear to be at the very best end of that spectrum."
If the Mercedes problem was indeed being created within the core of the tyre, if the W11 is essentially creating more downforce than the tyre can comfortably support around high-energy tracks on a hot day, then it may have to surrender some peak pace. Which would seem to potentially open another window of opportunity for Red Bull.