Less than 72 hours after concluding the Malaysian Grand Prix, Pirelli is preparing for the Chinese Grand Prix, round three of the 2011 Formula One World Championship. As was the case in Australia, the teams will have an extra set of hard compound tyres for use during Friday's first free practice session only. The allocation for the rest of the weekend is unaffected.
The hard and soft PZero tyres are nominated for the Chinese Grand Prix, with the aim of seeing at least two pit stops per car, in line with Pirelli's philosophy of promoting overtaking both on the track and in the pits.
The faster tyre wear compared to previous years can lead to strips of rubber being deposited on the track, which vary in size but are generally the shape and consistency of toffees, weighing between 10 and 20 grams on average. These strips are pliable when warm but become more rigid when they cool down, just like toffee. These rubber 'marbles' have always existed in Formula One, but the characteristics of Pirelli's new compounds mean that the pieces are on average larger and softer than the hard and round 'marbles' that have been seen at grands prix in the past.
A Formula One tyre, which weighs approximately eight and a half kilograms when new, will lose around a kilogram and a half as it wears over the course of a stint. With an increased number of pit stops, more rubber will be laid down on the track.
This phenomenon is not new in Formula One, but it is most pronounced at circuits where there is a high degree of tyre wear, like Malaysia. Pirelli is looking at ways to reduce these deposits in future, but rubber on the circuit is an inevitable by-product of degradation and the 'marbles' left on the circuit pose no danger to competitors or spectators.
The surface and weather in China is generally less aggressive than Malaysia, with conditions more similar to Australia. This means that there should be 30% less tyre wear and fewer pit stops than seen at the Malaysian Grand Prix, which provided a thrilling battle from start to finish.
The Shanghai International Circuit is characterised by rapid straights and very long corners, providing a tough test for the tyres. The track is 5.451 kilometres long with a race length of 305.066 kilometres after 56 laps on a smooth surface. The first corner tightens, putting all the strain on the front-left tyre: which will be cold at the beginning of the race. As this corner develops a sharper radius, aerodynamic grip decreases and the emphasis switches to mechanical grip. Leaving the opening complex the drivers change up rapidly through the gears, reaching 280 kilometres per hour in a breath-taking sweep up to the top of the circuit.
Turn 13 is the most challenging corner of the lap, where the left-rear tyre is subjected to a lateral acceleration that triples the normal load on the carcass. This is accentuated by the camber of the circuit, which suffers from subsidence in certain places.
At the end of the straight the drivers brake hard into a tight right-hand hairpin (turn 14) that is taken in first gear, scrubbing off the top speed produced by more than 830 horsepower in less than three seconds.
It's then up to the tyre compound to provide maximum grip to reduce wheelspin throughout the final crucial complex of corners that leads to the start-finish straight.
Pirelli's Motorsport Director says:
Paul Hembery: "We're looking forward to another thrilling race in China, although we don't want to disappoint anybody who says that we've made the races too exciting: it's true that if you get up in the middle of the grand prix now, the chances are that you'll miss something important! Once all the different strategies had played out, the last 10 laps in Sepang were absolutely thrilling - but you can't make an omelette without breaking eggs, or, in the case of Malaysia, rubber. The rubber 'marbles' on the track are a natural consequence of the increased degradation that has led to more exciting races: all that rubber has to go somewhere, just as it has always done in the past. Having said that, we're here to serve the teams' best interests and we're looking at ways of reducing some of the deposits in the future. But that's not going to change our fundamental philosophy: we want to give racing back to the racers."