Pirelli heads back to Barcelona for this week's rearranged F1 test session focusing on the tyre compounds that it will be providing for the first three rounds of the season.

Following the announcement that the Bahrain Grand Prix will not take place as the opening round of the 2011 campaign, as a result of civil unrest in the island kingdom, the planned pre-race test has been switched back to the Circuit de Catalunya - the venue for the most recent session - as the teams get one final four-day test to prepare for the year ahead. Although the session is due to take place from 8-12 March, the teams will test for a maximum of four days each, bringing their total number of pre-season days up to the 15 days agreed between them.

With Pirelli recently announcing the hard and soft PZero compounds that will be taken to the first three races in Australia, Malaysia and China, all twelve teams will concentrate their work on those this week, with the Italian firm bringing 35 sets of tyres per team to the Spanish Grand Prix venue. In addition, five sets of intermediate tyres and three sets of wet per team will also be on hand if required - considerably more than the two sets of intermediates and three sets of wets that had been earmarked for Bahrain.

Although there is some concern over the lack of wet-weather running during the pre-season so far, the teams will be hoping for warm conditions in Barcelona, in order to more accurately replicate the conditions that they are likely to encounter over the course of the season.

"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," Pirelli motorsport director Paul Hembery 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."

A priority for the teams at this week's test will be to complete set-up work that optimises the balance of the cars on the new PZero rubber. The compounds are identical for both front and rear tyres, but the rears - as is the case with all rear-wheel drive cars - warm up quicker because of the traction going through them. The front tyres take longer to reach ideal temperature, provoking a change of balance, which the drivers and engineers must make the most of by adjusting the set-up.

Despite criticism from drivers, Pirelli believes that the hard PZero compound offers a good balance between performance and durability, making it an ideal choice of prime tyre over a long run in warm conditions, while the softer tyre takes less time to warm up and is quicker over a shorter period of time, but is also designed to work at its best in temperatures of more than 15 degrees centigrade, the ambient conditions for the vast majority of F1 races.

"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 concluded, "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 pit-stops at every race."