During a recent visit to Milan, Italy we witnessed the introduction of Pirelli's 2013 motorsport program. It included new compounds for the Formula One season as well as a new 17" tires for the World Superbike teams, among other announcements (see our blog at europeancarweb.com).
Great emphasis was placed on how the new F1 tires would be softer than 2012, but also heavier as a result of a new construction that would provide better traction out of corners. One of the messages the company wished to deliver was that it's harder to create softer compounds with predictable degradation than a tire that can last the entire race.
It would appear that building a hard tire isn't particularly challenging. However, it would create a dull spectacle for spectators. In fact, even the F1 teams requested softer compounds for 2013 because they'd mastered the degradation rate of the 2012 tires and were able to accurately predict tire wear. This resulted in a number of teams running one-stop strategies that diminished the excitement towards the end of the 2012 season.
Getting a tire to degrade at a set rate without a dangerous failure is an art Pirelli has happily embraced. In fact, they gave us a tour of the engineering and research facility to illustrate the on-going development.
Perhaps the biggest surprise was that Pirelli based its first F1 development tires on its road-going P Zero products, using them as a starting point for further testing. And yet now, several years later, F1 is producing improvements for street tires, particularly in terms of construction, handling and wet weather tread patterns.
With 1200 technicians involved in R&D around the world, of which 400 are based in Pirelli's Milanese HQ, the company devotes 7% of annual turnover to research. The test facilities include everything from chemical labs examining compounds at the molecular level. The findings are translated into new compounds that can quickly be turned into slick tires. A laser system then cuts shallow tread patterns into the surface, after which the full tread depth is hand-cut.
This prototyping method is significantly quicker and cheaper than producing complex molds for each tread pattern and the tiny variations that might be required. The technique is used primarily for road tires but has been used for development of F1 "wets" as well.
Once a compound and tread pattern has been produced, prototypes are put through a number of tests, including a static tire footprint pressure test. This allows engineers to see how the carcass deforms in order to assess the structure.
The tire then moves to the dynamic laboratories where it's mounted and spun on a drum up to 155mph (or 280mph in the F1 tests). The rig is then able to simulate different loads, camber angles and slip angles to see how the tire performs and to assess wear rate, temperature, etc. These machines can even simulate racetracks, so engineers can simulate a race at full speed to examine the tire's performance.
However, it's not all about racing. A team of 70 people run up to 20,000 tests each year to meet homologation requirements and provide vehicle manufacturers with specific tire data. This allows carmakers to pick specific tires for their products, or tune suspension to suit the characteristics. And with Pirelli having so many OE supply contracts, this side of the R&D department is very important.
Once a tire has been fully developed and approved for production, the relevant molds are made. Most of its regular tires are produced in one of Pirelli's massive factories located in 22 countries around the world. However, the high-performance, low-volume tires are produced in a revolutionary way known as Next MIRS.
As its name suggests, this is an evolution of Pirelli's MIRS system and is fully robotized, with employees on-hand only to oversee the operation and ensure the supply of raw materials.
Housed in a separate building, Next MIRS is a modular system capable of being delivered to any location, such as a sports car maker, where it can produce up to 100 tires per day, compared to 750 tires from each machine in a conventional factory.
Taking the basic elements of the tire, such as the steel and composite belts, carcass, tread compound and bead, the structural elements are first weaved into belts and extruded into rubber strips. The strips are then wrapped around a steel drum at high speed to form the inner carcass. Without glue, the tacky rubber forms one piece merely by applying sufficient pressure.
The outer tread section is formed using the same method, laying strips of extruded rubber over another drum, each of which is adjustable for width and diameter. As the strips are laid down, the outer section forms in a matter of minutes.
With another robot adding the tire bead to the carcass, the tread is placed around the inner carcass, which is inflated under high pressure to create a complete tire that again becomes one piece thanks to the tackiness of the components.
All this "green" tire lacks is its final shape and tread pattern. So it's placed into its final mold. A rubber bladder is then placed inside the tire and 12psi of steam pressure forms the internal shape. The mold also stamps the tread pattern into the malleable rubber, after which each mold is placed into an oven where it's vulcanized into the final product. Every tire is then inspected by hand and x-ray to ensure consistency.
During our trip, we saw tires produced for the Ferrari F150, Viper, Aventador, McLaren MP4-12C and 911 GT3. These are among the most powerful cars in the world and all are fitted with OE Pirelli tires produced using the Next MIRS system in front of our eyes under laboratory conditions. So next time you're watching F1 or kicking the tires on your favorite sports car, you'll have a better insight into how they got there.