Tough choices on tyres at Silverstone

Due to its mixture of fast and medium corners, the former airfield track is something of an unknown when it comes to rubber. Williams is the lead Michelin team and will be keen to maintain the momentum in its battle with Bridgestone rivals Ferrari, so the choice of tyres on offer will therefore be key.

"Silverstone requires a harder tyre than the last few circuits," said Williams chief operations engineer Sam Michael. "The circuit has a good mixture of low, medium and high speed corners. High speed sections mean that tyre degradation is an issue and as such, selecting between Michelin's Prime and Option tyres will be a difficult choice."

In recent races Williams drivers Juan-Pablo Montoya and Ralf Schumacher have suffered for pace as their tyres go off in the middle section of race stints and then improve again towards the end.

What is more, Schumacher Jr lost a lot of time due to a poor second set of tyres during the French Grand Prix, causing concerns over consistency. With Silverstone's unique characteristics, solving problems won't be made any easier this weekend. Montoya said of the Northamptonshire circuit: "Silverstone is a bit of a question mark on the tyres."

Bridgestone, which supplies both Ferrari and McLaren, is of course faced with exactly the same problems as its French counterpart and according to Bridgestone Motorsport's technical manager Hisao Suganuma, the variety of criteria which must be met for the Northamptonshire circuit makes selecting the right tyre something of a lottery.

"Silverstone's combination of high-speed and slow corners requires good balance and tyres that give stability under braking and in cornering," said Suganuma. "The challenge lies in finding a tyre to suit all Silverstone's characteristics - concentrate too much on stability through the fast corners and you may end up with not enough grip in the slow corners.

"The surface at Silverstone is quite abrasive compared to recent tracks, so the tyres must have a good wear rate and heat durability in order to keep degradation to a minimum."

Bridgestone runners will use a compound chosen during testing at Silverstone in June, whereas the Michelin teams are thought to have been carrying out final evaluation work at Monza last week.