Why F1’s switch from 13-inch to 18-inch tires is important

 

Formula One goes to Abu Dhabi this weekend. When the checkered flag waves and the fireworks fly on Sunday night, a thrilling season will end with either Lewis Hamilton or Max Verstappen emerging as this year's champion.

 

But the Abu Dhabi Grand Prix doesn't just mean the end of an exciting year of racing—it also marks the end of an era as the sport prepares for a radical change to its tires. For decades, F1 cars have run on 13-inch wheels, wrapped in tires with high-profile sidewalls. But as part of 2022's radical technical shakeup, the sport is now joining much of the rest of the racing world as it adopts 18-inch wheels and new, low-profile racing rubber.

 

There was a lot of freedom in wheel size and choice for F1's first few decades, which might shock those accustomed to the current sport's rigid and prescriptive rulebook. The move to standard 13-inch wheels happened in the 1980s at a time when 13-inch wheels were still often fitted to road cars—albeit smaller, cheaper ones.

 

The limit on wheel size was enacted as a way to stop teams from fitting ever-bigger brakes to the cars; a lot of overtaking happens in the braking zones, and a consequence of reduced stopping distances is that overtaking becomes much harder. This helpfully shows that complaints about the absence of overtaking in F1 are nothing new, and if you're wondering why officials didn't they just mandate the brake diameter in the same rulebook that mandated wheel diameter, that did eventually happen.

 

For years, the choice of tires in F1 was also relatively open, with competition between tire manufacturers as recently as 2006. But since 2011, it's been a one-brand show after Pirelli won the contract to be the sport's sole tire supplier.

 

This has been a potentially perilous position for Pirelli. In a tire war, manufacturers and their partner teams work together to improve grip and durability, with the aim of getting to the end of the race before anyone else. But as the sole supplier, Pirelli was tasked by the F1 powers-that-be with delivering tires that would spice up the show. More often than not, we just got lots of complaints from drivers instead, particularly if a tire ruined their race.

 

"It's the biggest issue we have, because clearly we are the supplier and received a request from different stakeholders for F1: What is important is to have a great show to sell to the world," said Mario Isola, head of F1 and car racing at Pirelli. "For drivers, what is important is to have a lot of grip, no degradation or overheating, and push, push, push," he explained.

 

That led to meetings between Pirelli and the teams and drivers to agree on the characteristics for the tires. "For example, for next year, there is a request of overheating reduction, there's a request to have a wider working [temperature] range, and there is a request to have a delta time between compounds that is around 0.5 seconds per lap," Isola told me.

Pirelli will still bring three different compounds of tire to each race—a soft, a medium, and a hard—and we can expect them to be a bit more durable than the rubber that fans have witnessed in recent years. "It's not zero degradation," said Isola, "because zero degradation is not good for the show, and it's not encouraging any different strategy, but it is a compromise that is making more or less everybody happy."

 

The new tires will have the same tread width as before—305 mm at the front and 405 mm at the rear—but the overall diameter of the tire is increasing to 720 mm (from 660 mm). That means slightly larger (and differently shaped) contact patches.

 

The new tires have been developed using a mix of simulation and track testing, with specially modified cars meant to replicate some of the other big technical changes coming to F1 in 2022. There are a few things to look for. "The cooling system of the brake will be completely different compared to this year," Isola told me.

 

Until the end of this year, teams have played with brake cooling to heat the wheel rims and tires (F1 brakes operate at between 400-1,000° C, and that heat transfers to the wheel and tire). That changes next year. The brakes are staying the same size and will now be surrounded by much more air inside the rim. The cars will gain wheel covers, which will affect tire heating and cooling.

 

F1 engineers will also have to throw out most of what they've learned about setting up an F1 car's suspension, too. Not only are the new wheels and tires heavier, but currently, the hefty sidewalls on the 13-inch tires do most of the springing, something you'll regularly see in slow-motion replays. In 2022, that job goes back to the actual springs in the suspension.

 

"We were a bit worried about the impact on curbs, especially on circuits with very high curbs," Isola told me, ironically just a couple of weekends before the curbs of the Losail International Circuit in Qatar (which doesn't usually host F1) damaged several tires. "But talking to the drivers, they reported no issues [with the 2022 tire]," Isola said. "They could drive without changing the driving lines and so on. So that's good feedback for us."

 

You may be wondering what Pirelli gets out of all of this. Yes, there's a marketing value, but the company could also spend that money on different kinds of advertising instead. But it seems Pirelli does find avenues for technology transfer, despite the radical differences between F1 and road cars.

 

"It is true that the tread compound is designed to work at 120° C—that is something that never happens on the road, unless you are crazy, and then the police will stop you very soon," Isola told me. "But there are a lot of other elements that we can use in Formula One. And we learn from that."

 

"In terms of vehicle models, in terms of materials, production processes, quality controls, indoor testing that is representative of what happened on track, obviously you can make the same for on-road tires—there are a lot of areas in which we develop technology that is applicable to road tires. It is not the tread compound because the tread compound is designed to last for 150 kilometers and 120 degrees," Isola explained.

 

"What is claimed in the Formula One is for sure the extreme limit—the acceleration, the top speed, the downforce," said Piero Misani, head of R&D at Pirelli. "The lateral forces in F1 are by far the highest that you can have in any kind of car competition."

 

Some of that is due to materials. Misani said that Pirelli experimented with liquid polymers for the base of the tire compound and grip-promoting resins in F1 before transferring those ideas to its standard road tires, as well as a new hybrid cord construction.

 

Next year's move to much more road-relevant 18-inch low-profile tires should help that technology-transfer process. But mostly, let's hope the switch makes for good racing.