Mat Coch writes:

Teams reaching the final phase of qualifying for tomorrow's Singapore Grand Prix face a difficult decision when it comes to picking a winning strategy.

Pirelli has brought both the soft and supersoft tyre here this weekend, with teams experiencing a significant difference in lap time between the two compounds during Friday practice.

The softer, faster compound rubber, the red-walled supersoft 'option', is as much as a second and a half a lap faster than the slightly harder 'prime' tyre, though it gives up grip dramatically. "Degradation on the supersoft is about three tenths a lap, so quite high," Paul Hembery revealed after practice.

The Pirelli boss also claimed there was no 'cliff', as has been experienced at some races this year where tyres suddenly and dramatically lose performance. "It seems quite linear at the moment," he explained, "so cross over (is) after about five laps between the two."

The harder compound tyre, while slower, loses just a tenth of a second a lap, posing difficult questions for the team's strategists.

With just five good laps before the supersoft tyres begin giving up their advantage teams that qualify in the top ten will face a nervous first stint. Pitting early will likely save them falling in to the clutches of the chasing pack as their lap times slow, but pitting too early will see them back on track among the midfield.

Fuel burn is expected to count for a little over a tenth of a second a lap, off-setting degradation to some extent on the 'prime' tyre and adding to the teams' headache.

With a pitlane time of about 28 seconds smart money is on a three-stop strategy. That decision will be performance driven rather than wear; the tyres are easily capable of a two-stop race in terms of wear but the drop in performance makes it a much slower strategy.

The critical factor however will be making the supersoft tyre last. While Pirelli expects five good laps some teams are burning through them in just two. Managing that degradation and maintaining the performance will stand a driver in good stead, a situation which seems to bode well for the light-footed Saubers.