Pirelli is crafting unique rubber-led compounds for its 18-inch F1 tires.
- Pirelli has been the sole producer of F1 tires since 2011.
- Testing is happening now on changes to the F1 tire for 2023, including the addition of a sixth dry compound.
- Rubber compound warming is a significant issue both now and for the future of F1.
With speeds reaching over 200 miles per hour, Formula 1 vehicles place a pounding on the rubber tires tasked with gripping the asphalt. Since 2011, F1 teams have relied on Pirelli, the maker of all F1 tires, to build tires that can handle the savage power and downforce produced by a Formula 1 car.
“There is a balance in a lot of the choices we have. The balance is a trade-off from performance, durability, and integrity,” Maurizio Boiocchi, Pirelli executive vice president and strategic adviser of technology and innovation, tells Popular Mechanics while speaking from his office in Italy. “This is the magic in which we have to develop.”
Now, for 2023, Pirelli is adding a sixth dry compound to the tires and making small tweaks, all while improving the understeer in low-speed corners and tuning the wear profile, Mario Isloa, Pirelli’s motorsport director, tells Popular Mechanics.
The intense conditions placed on an F1 tire far surpass what a regular tire goes through on public roadways. A tire crafted from less than 22 pounds of material endures 2,000 pounds of vertical load, all while running 200 miles per hour, supporting 3.5 tons of force, and handling 5G longitudinal force. These conditions—which can mean tires handle forces six times the weight of the vehicle—place a stress on an F1 tire that does not exist anywhere else, Boiocchi says. “We must have specific technology to resist these conditions.”
The 2022 season saw a major change to the tires, with F1 expanding the tires from 13 inches to 18 inches, including a smaller sidewall that deforms less. The new tires were designed from the ground-up, with a fresh profile, structure, and compound. The 18-inch tires reduce overheating with a more evenly distributed contact patch to the ground. This also allows for greater stability and consistency, which improves feel.
Understanding F1 Slicks
In 2022, Pirelli created five different slicks, each with their own compound—labeled C1 to C5, with C1 the hardest—along with two rain tires, an intermediate, and a full wet. During each race, F1 allocates three of the five dry-weather varieties for use. With intricate rules dictating tires used, all drivers must use two different dry compounds during a race.
For 2023, get ready to welcome a sixth dry compound, slotted between the current C1 and C2 hardness.
The internal structure across all dry slicks remains the same, essential in maintaining the balance of the vehicle. When a tire change is made, teams are simply “managing” the compound softness instead of an entire vehicle setup, Boiocchi says.
An F1 tire is made of a metallic bead, the innermost section of the tire, and a textile fiber carcass. It’s filled with nitrogen instead of air for a reliable pressure throughout the race. A belt wraps the carcass. From there, the outer compound, roughly half a centimeter thick, connects to the belt and ties the tire to the driving surface.
The famous slicks of F1 racing ensure the most contact with the ground. The range of compounds, which Boiocchi describes as a “very complex mix of components,” includes both natural and synthetic rubber, filler, and additive materials, all part of the recipe that helps provides grip.
Isola says each compound has unique ingredients to define the hardness of the tire.
The Differences in Compounds
Compound 1, which will be renamed Compound 0 in 2023, is the hardest in the range and is designed to provide maximum resistance to heat and extreme forces, capable of running long stints with minimal performance drop-off. Conversely, Compound 5 is the softest, commonly designed for the slowest (but not always) circuits with low wear and degradation where maximum grip is required from the rubber. These are most seen at street circuits or where the asphalt is exceptionally smooth.
Compound 2 is common in new circuits, where the circumstances are relatively unknown, while Compound 4 is popular for low-severity circuits, “where a quick warm-up is required in order to hit peak performance immediately,” according to the Pirelli website. Compound 3 is used at every event, sometimes the hardest of the three compounds, sometimes the softest, and sometimes falling in the middle.
DIVE DEEPER ⬇️
With “grip very important,” the surface plays a key role in the tire choices for teams, Boiocchi says. Mechanical grip, a key part of a hard tire, is the ability of the tire to integrate with the roughness of the asphalt track. The adhesive grip, relied upon for the softest tires, is a chemical grip generated between the compound and road.
The smoother the surface, the smaller the area in the asphalt the compound can penetrate to create mechanical grip on the tire. Teams will make decisions on which compound they use in a race based on a device that scans the surface to determine roughness frequencies.
“You have more adhesive grip on softer compounds, while the harder compounds rely more on mechanical grip or asphalts with a higher roughness,” Isola says.
Adding a Sixth Compound
F1 will add races for 2023, bringing the total number of circuits to 23. Pirelli added a sixth dry compound to match the increase in asphalt types. Isola says they discovered the difference between the C1 and C2 compounds was more pronounced than the C2 and C3 shift.
“With six compounds,” Isola says, “teams are ready to react. Maybe on a high-severity surface we need C0, C1, and C2. The level of stress [on tires] is growing and growing and we are reacting with harder compounds.”
Temperature Importance
Temperature plays a key role in producing grip from the rubber-based compound, and overheating is always a give-and-take discussion. Tires must warm up to generate the required characteristics, falling within the “working range.” For example, a polymer additive mixed into the compound is nearly like glass when cold, but when it warms up, it offers an ideal grip. “This [compound] design works on a range of temperatures, so your grip is maximized,” says Boiocchi.
Teams use tire blankets to warm tires before mounting them. New rules in 2022 limited the blankets’ temperature to 70 degrees Celsius—down from 100 degrees—all part of an effort by F1 to reduce electricity during races and eventually phase out the use of blankets altogether. Boiocchi says that these changes require new compound formulas. “To make a compound to heat up is very easy,” he says, “[but] it is difficult to stop. This is the challenge we have for the future.”
Each compound offers a different working range. The less severe the surface, the less energy put into the tire, generating less heat. The harder compounds offer stiffer tires, which handle more energy from the track. This equates to more heat, giving the harder tires a higher working range. Isola says that the concern with soft tires on a low-severity surface is getting the tires warmed up to the working range, while hard tires on a high-severity surface warm quickly and they must reduce overheating.
“The grip of the tire is a function of the temperature,” Isola says. “We try to design a compound with a wide working range as much as possible. We move this working window depending on where we want to use the tire.”
F1 Wet Tires
Pirelli also makes two types of wet tires, each for the differing amount of rain on the track’s surface, sanding or otherwise. The “intermediate” tire features 3.4 to 5 millimeters of tread, allowing a vehicle traveling nearly 200 miles per hour the ability to shed 25 to 30 liters of water per second.
For even more severe weather, Pirelli offers what was once called a “monsoon version.” Now it is simply called the “full wet,” with a more aggressive tread pattern even deeper than the intermediate that can displace 65 to 75 liters of water per second. The full wet also features a softer compound than the dry tires.
The full wet version is rarely used because by the time teams switch to the full wet, the race is often flagged to a red stop for safety conditions that include an increased risk of hydroplaning and decreased visibility.
Along with the tread patterns, the two wet tires have a slightly larger diameter to raise the vehicle “a little higher to avoid the floor of the car splashing the water and making for lost control of the vehicle.”
The behind-the-scenes work of the F1 tire never stops. “The tire is not an easy product,” Boiocchi says. “It is a product that is very sensitive to many conditions, temperature, surface, driving style. Any detail is very important in our field and what we learn from Formula 1 is very useful to do better on our best performance product.”
This article was first posted: https://www.popularmechanics.com/cars/car-technology/a42051244/formula-1-tires/
