Rain tyres - the secret of Bridgestone's success.

The British Grand Prix at Silverstone on Sunday underlined the dominance of Bridgestone's tyres in the rain, with another victory for Michael Schumacher - the 60th of his F1 career - and second place for his Scuderia Ferrari Marlboro team-mate Rubens Barrichello only the beginning of the celebrations enjoyed by Bridgestone's teams.

Lucky Strike BAR Honda scored its first points of the season with magnificent fourth and fifth places for drivers Jacques Villeneuve and Olivier Panis, and the day was rounded off with another point for Nick Heidfeld which helped move Sauber Petronas closer to fourth place in the constructors' championship. Giancarlo Fisichella was the sixth driver on Bridgestone tyres in the top seven. Meanwhile, OrangeArrows driver Heinz-Harald Frentzen was able to chase a McLaren Mercedes after changing to Bridgestone intermediate tyres, having moved up to a potential points-scoring position from 16th on the grid.

The competitiveness of Bridgestone's intermediate tyre, chosen by all its teams at the first pit stop, was clear for all to see - "the Bridgestones were simply flying" was the comment of one driver on the alternative brand.

While the British Grand Prix was the only wet race of the season so far, there had been prior indications of the performance of Bridgestone's intermediate tyres as far back as the free practice sessions at the San Marino Grand Prix.

However, it has not always been that way. Indeed, Bridgestone's poor showing in the DTM series race at N?rburgring in 1992 marked the final straw in what had been a lean period for the manufacturer's wet tyre performance going back to Formula Two a decade earlier.

"The performance of our rain tyres at N?rburgring in 1992 can only be described as a disaster - we were seven or eight seconds slower than our rivals," Hisao Suganuma, technical manager of Bridgestone's F1 programme, explained, "We realised then that we had a lot of work to do and this was motivation enough to do better."

From that point, the company's researchers and engineers at the technical centre in Japan began to analyse closely each part of the tyres' performance - construction, compound and pattern. The latter two appeared to have the most influence over the tyres' competitiveness and, by the next DTM race, improvements had been made. Not too much detail can be given about compound development since then, particularly in the company's F1 wet tyres, but, in short, the way a rain tyre works depends on the chemical reaction between the rubber and water.

In terms of pattern, development is about identifying the right land:sea ratio - that is the size of the contact patch between rubber and road [land] and the amount, depth and shape of grooves to drain water away [sea].

"If one increases the sea ratio [ie. the number of grooves], the blocks will be smaller, which means there is less contact patch on the road," Suganuma explained, "This causes more force to be put through the blocks which, in turn, causes more movement in the tyre. This can make the car feel unstable and ultimately make it slower.

"An intermediate tyre, designed to be used in damp conditions, has bigger blocks to increase the stiffness and make the tyre capable of going faster through corners. In this case, the sea ratio is decreased, making the tyre less able to disperse water. Consequently, intermediate tyres are not appropriate when it is raining heavily or there is standing water on the track."

Despite having this knowledge, when Bridgestone first entered Formula One in 1997, the only way of proving its rain tyre performance was to design a pattern using existing technology in the laboratory and then track test it.

However, this approach was advanced considerably with the introduction of Bridgestone's exclusive Hydro Simulation Technology. Using computer software, for the first time researchers were able to realistically simulate tyres travelling through water.

"We used this cutting edge technology to see what we could not see before with our eyes," Suganuma pointed out, "From this information, we were able to develop a pattern which efficiently disperses water and works in harmony with the compound."

The result is Formula One intermediate and wet tyres that look quite different to Bridgestone's competitor's tyres. The intermediates have vertical and lateral grooves which evacuate the water from the tyre as a whole, and small cuts called sipes that disperse the water from the individual blocks.

"We have worked hard to develop the best tyres for wet conditions that we can, and I think Sunday demonstrated how that has paid off," Suganuma concluded, "Nonetheless, the work continues...."