Why Pirelli is already doing what Verstappen told it to do with the C6 F1 tyre

When Pirelli announced the arrival of a new member of its tyre-compound family pre-season, Singapore and Las Vegas was on the list of possible venues where the ultra-soft C6 tyre could be used. This plan had been dropped even before Max Verstappen made a remarkable outburst after qualifying for the Azerbaijan GP.

“You’re really better off leaving it at home,” was his summary. The C6 will now not be seen again this season, though there will be an equivalent tyre next year.

In fan conversations on social media and other online forums there are often individuals who argue in favour of softer tyres, in the mistaken belief that these will automatically lead to more exciting and unpredictable racing. But F1 is a scientific endeavour as well as a competitive one and the C6 is a prime example of why this apparently simple and obvious solution is unworkable: it’s so soft that getting a single push lap out of it is a challenge.

Note also that the tyre allocation for the Sao Paulo GP is a step harder this year – because last year Pirelli went a step softer and the outcome was that the softest choice “was not a viable race tyre”.

At some grands prix, but not all, the soft can manage a race stint as well as being a qualifying tyre. But this hasn’t been the case with the C6.

Where the C6 has created unpredictability, it has done so in an unexpected and not always desirable fashion, although this hasn’t stopped Pirelli claiming that as a win. Chiefly this uncertainty has come in qualifying, where some teams and drivers prefer the C5, which has a knock-on effect in terms of the compounds they have left available for the race.

So this does have an effect on strategy, albeit not in the manner originally intended. Hence Verstappen’s rant.

“I think I should have a conversation with Pirelli at some point and tell them to just leave that tyre at home, because it makes the whole weekend very tricky,” he complained. “You have no proper reference on the mediums until qualifying. It doesn’t make any sense. Look, if the tyre doesn’t work here… It didn’t work in Monaco, it didn’t work in Imola, and in Montreal it didn’t work either.”

The C6 was formulated with the best of intentions: not quite to force teams to make more pitstops in races, but to introduce more strategic variety by making the choices less clear-cut. Generally speaking, teams will default to as few pitstops as possible – usually one – to guard track position.

To make a multi-stop strategy worthwhile it has to be meaningfully quicker than a one-stopper, and this is a tricky balance to strike. Overshooting, and making a one-stop too slow, would push everyone to stop more than once, negating the benefit – because generally people on similar strategies stop at the same time.

For this reason, Verstappen’s claim in Baku that “it’s better to just force a two-stop rather than bring a tyre that isn’t actually any faster” does not stand up to interrogation.

Tyre choice for each circuit is based on the demands it places on the rubber, the most influential factors being the abrasiveness of the surface, typical cornering speeds, and ambient temperature. Pirelli has improved the thermal degradation characteristics of its tyre compounds this year, enabling it to go a step softer at several races, but this hasn’t had the desired effect of promoting multi-stop strategies.

Lando Norris, McLaren

Photo by: Joe Portlock / LAT Images via Getty Images

The C6 formed part of this plan, creating an even softer choice, but the execution has been slightly flawed. It hasn’t been decisively faster than the C5, and has been harder to manage: its peak performance doesn’t last long enough and a single slide can make the surface temperature spike beyond its operating range, killing off grip. Also, as the surface heats up it moves around more than the C5’s, transmitting a disconcerting and confidence-sapping vagueness to the driver.

For all these reasons the C6 has only been used on tracks which exercise the least demand on tyres, and the plans to roll it out in Singapore and Las Vegas have been shelved. The tyre selections for the remaining rounds were announced at the beginning of August under the headline “Changes and status quo when it comes to compound choices for the rest of the season”.

Well, it was certainly Margarita Time for those not wishing to use the C6 again this year. Or not, since there is a window for the tyre supplier to change its mind until four weeks before the race, so the C6 hasn’t quite burned its bridges.

In Baku, Mercedes trackside engineering director Andrew Shovlin suggested that it would have been better to have a step between the harder compounds than to go softer.

“I’d have probably preferred it if we kept the C5 [as the soft choice], which is a good tyre that works,” he said. “And then they actually change the C3 for a C1 or something, give you a tyre that’s so hard it doesn’t grip. And then no one’s going to want to one-stop it.”

While the C3 “made a one-stop very easy [in Baku] last year”, the C4 did that last weekend – as did the C5, on which many drivers ran very long first stints. But would the C1 be too hard?

Lando Norris, McLaren, Oscar Piastri, McLaren

Photo by: Erik Junius

Pirelli has already experimented with having a step between the harder compounds this season, in Belgium, where the weather prevented a proper evaluation. It will try again in Austin and Mexico City.

Meanwhile the C6 is not going to go away – but when it comes back, it needs to be better.

“What I would like for the future is a C6 with more gap to the C5,” Pirelli motorsport manager Mario Isola emphasised after the Canadian GP.

“Now it is around two tenths of a second, we need to have at least half a second. So even more aggressive with a level of degradation that is similar to what we have now to generate different strategies.

“For next year, we are working on a C6 with this target.”