Final test to reveal true tyre picture

All four Pirelli compounds have been available in the winter tests held so far, but for this week's Catalunya session only the hard and soft tyres will be in use, as these compounds have been chosen as the selection for the first three grands prix of the season, making this the most representative test so far according to Pirelli's motorsport boss Paul Hembery.

"Having announced our compounds for the start of the year, most of the teams will concentrate on testing the hard and soft PZero tyres," Hembery said.

"We're expecting them to focus on long runs and race simulations, which should confirm the results we have previously extrapolated from our testing data: two or sometimes three pitstops at every race."

The likelihood of an increased number of pitstops in 2011 has been one of the key topics of the winter, with Pirelli deliberately designing its rubber with less longevity in the hope of spicing up the action through tyre wear and strategic variety. But this move has drawn criticism from some drivers.

McLaren's Lewis Hamilton said at the previous test that the driving style required to make the Pirellis last through a stint was "like driving an out-lap, very slow and not particularly exciting. It lasted a little bit longer but it didn't feel like I was really racing the car."

Fernando Alonso has also argued that introducing too many pitstops will lead to chaotic races that penalise the top teams.

"From what we have seen so far, degradation is very significant, which means we will have races with lots of pitstops," the Ferrari driver said at a sponsor event last week.

"I'm not keen on that because I think this increased uncertainty does not favour the strongest teams. It's as if in football, it was decided to have a penalty per team each half hour in which case Barcelona and Real Madrid would not be jumping for joy."

Hembery pointed out that low temperatures so far this winter had made testing conditions unrepresentative of likely grand prix weather. He suggested firm judgements about tyre wear and pitstops could only be made if conditions warmed up for this week's test.

"Our last test in Barcelona was held in temperatures of just six degrees in the mornings, which didn't help to rubber the track in or gather the information necessary to base strategies on over the course of the season," he said.

"We're hoping for warmer weather this week, although it's unlikely to be as warm as the temperatures we are expecting for the first race in Australia."

The Red Bull drivers have been more open to the change in strategy, with world champion Sebastian Vettel admitting that three pitstops were likely, but intrigued rather than concerned by this.

"I think one stop is impossible and at this stage also two stops, so I think it will be a three or four-stop race. I think it will make it very interesting," he said.

"The question is if it is a good thing for us or a bad thing. It's hard to say now because obviously we have to get going first and see how the races unfold."

His team-mate Mark Webber warned that tyre performance in testing could be irrelevant when the season starts.

"This has happened in the past. Last year at Jerez we were completely s**tting ourselves with the Bridgestones doing long runs, thinking 'oh my God, we're going to be stopping every...' you know, then we get to the first races and drive around all day [on one set]," he said after the last test. "We need to go racing."

But at present he feels the Pirellis' characteristics are adding to the challenge for drivers.

"It's easier for us to look average," said Webber. "You're even talking to yourself in the cockpit 'come on Mark, that was messy, that was scrappy', it's very easy to be losing time when the tyre goes away a little bit, so you've got to have that in mind."

The Barcelona test commences tomorrow, with the majority of teams running until Friday. But Williams, Mercedes, Ferrari and HRT will start a day later than their rivals on Wednesday and run through to Saturday instead.