Pirelli: Hard- or soft-tire choices steer path to grand prix victory

Most cars opted to use the hard P Zero tires in the first session, which have been nominated as the prime tire for Australia, before switching to the soft tire for the bulk of the second session as the crews refined their racing strategies.

“We’re pleased with our first outing under competitive grand prix conditions, as our tires have already shown a good level of performance and durability,” says Paul Hembery, Pirelli’s motorsports director.

“While the weather may have felt cold for Australia, these were actually some of the warmest conditions that we have run in recently, and already we can see that our rubber is working better at these temperatures. We’re in for a very exciting weekend: Even with all the information that we have at our disposal, it’s still hard to predict exactly how all the action will unfold.”

Compared to the supersoft – the most aggressive compound of the range – the soft tire is 25 percent harder and the hard tire is 170 percent harder, meaning that there is a 145 percent difference between the two tires available to the 12 teams in Melbourne.

“We’ve worked hard for more action together with all the teams and now we can finally get going,” says Hembery.

“ It wasn’t easy to find the best balance in terms of tire degradation, which would promote pit stops and enhance the show, as we were requested, but at the same time ensure that the tires did not deteriorate too rapidly or too slowly,” he explains.

“In GP2, where the cars and the tires are quite similar to Formula One, it was a lot simpler,” Hembery adds.

“The teams asked us for structural reliability rather than variable degradation, and after the first few races we know that we have come up with a long-lasting tire that everybody likes,” he reports.

“What’s certain is that our P Zero Formula One tires are structurally extremely reliable and can guarantee safety. The degradation is not immediate, but it is enough for the driver to feel a gradual drop off in performance over the course of a stint and then decide whether to change tires or not. This is where strategy comes into play. In Australia our target is to see between two and three pit stops per car,” Hembery points out.

The choice of the hard tire, which is the most durable P Zero compound, was influenced by the characteristics of the Albert Park track, which combines a medium aggressive surface with constant changes of elevation, speed and direction. For the same reasons, the soft tire has been chosen too, he says, going on to provide additional details: The Albert Park circuit, which is 5,303 meters long and takes in 58 race laps that total 191.117 miles, is home to a wide variety of conditions on a surface that is not greatly rubbered-in. “This has a profound effect on tire wear.”

Another important factor governing tire wear is the comparatively high level of downforce used, which is necessary due to the quick succession of corners and absence of long straights.

A place where the tires and cars are worked especially hard is the Sport Centre corner. The drivers scrub off 124 miles per hour in just 2.5 seconds and 108 meters under braking, subjecting themselves to a 5G deceleration while the front tires are pushed into the ground by 2535 pounds of downforce.

Shortly afterwards there is another challenge; a long right-hand corner that is taken flat-out, with slippery asphalt that can provoke oversteer and therefore tire wear.

The drivers then enter the most technical part of the track, which is also the most demanding – a blind bend taken at around 155 miles per hour, where it is important to stick to the part of the circuit that is most rubbered-in so as to take maximum advantage of the grip available. This is part of an S-bend complex, with bumpy asphalt that can destabilize the car. Being only a semi-permanent facility, the track has very little rubber on it at the start of the event, which has an inevitable effect on tire performance.

Waite corner is one of the key points of Albert Park. The exit speed from the corner is in the region of 130 miles per hour. The stressed front tire (on the outside of the curve) is operating at around 221 degrees F., whereas the inside tire on the right has slightly less work to do and runs nine degrees cooler at around 212 degrees. The rear tires, which provide the traction, operate at temperatures in excess of 212 degrees.

Another important area is the braking zone between turns 14 and 16, which loads the front of the car heavily leading into a chicane with tight right-angle corners before the main straight; the only place on the track where the cars top 186 miles per hour in seventh gear, and a key overtaking opportunity.

The size of the tire’s contact patch with the ground varies according to speed and aerodynamic load. At 186 miles per hour the contact patch of the tire is around three times what is when stationary, offering optimal traction and grip.

For more information, visit www.us.pirelli.com.