Button outlines importance of no rain in Spain

Perhaps the least significant change to a Formula One car has been under the spotlight here in Barcelona. Ferrari have been forced to remove the controversial barcode on their engine covers after watchdogs ruled it amounted to subliminal advertising for a tobacco manufacturer.

So far, so amusing. But this race will see plenty more important changes than that. Spain marks the start of the European leg of the world championship and is traditionally a crucial event for teams looking to make changes that actually affect how fast their car will go.

"The opening four races just underlined the general trend of winter testing," Fernando Alonso said yesterday. "But from this race on the development race will really get under way. Now that we are in Europe it's time to show who is going to fight for the title and who isn't."

This is where the major players will first try the development parts manufactured back in their opulent factories ,based on the lessons learnt since the championship fight kicked off in Bahrain in the middle of March. That is why both Jenson Button and Lewis Hamilton were so keen to stress why they need a dry race here, even though the wet races thus far have yielded Button two dramatic victories. "It's important we have a dry weekend," the champion said. "If it's wet and we have a good race, it's great and we get some good points. But we need to know where we are, to work with the car we have and with the new parts we have. It's an important race for us, for everyone, this weekend, to know where they stand in comparison to others."

Mercedes have probably the biggest upgrade of the top four teams fighting for the title. Michael Schumacher has a new chassis, albeit to the same specification as his previous one which sustained some damage in the four races so far, but of greater impact have been the revisions to the weight distribution to improve the handling. The front suspension is new and swept forward to increase the wheelbase and put the weight more where team principa,l Ross Brawn, wants it, while a dramatically shaped new engine cover and engine air intakes are part of the aerodynamic enhancements. Schumacher said he was much happier with the car after practice yesterday.

McLaren have new front and rear wings, and minor aero tweaks to the underfloor, all aimed at increasing downforce without increasing drag.

Ferrari have their "blown rear wing" – their version of McLaren's so-called "F duct" which stalls airflow over the rear wing at high speed, reducing drag and thus enhancing straight-line speed – and sundry minor aero modifications to effect improvements in airflow.

Red Bull were fastest in practice yesterday and generally agreed to have the quickest car, with Sebastian Vettel and Mark Webber locking up all four pole positions thus far. They have only one win to their credit, in Malaysia, but they do have what a team insider described as "yet another major upgrade" to their RB6. This embraces the front and rear wings, bodywork and undertray, all in the interests of increased downforce and speed. So far this year, this team's work rate seems to be the highest in terms of ongoing development.

Further down the grid the recent volcanic ash problems frustrated Virgin's hope of having two heavily revised cars available this weekend, but their lead driver Timo Glock has a VR-01 which at last has a large enough fuel tank to go a full race distance. An error of calculation in the design of the original car meant that in Malaysia Glock's team-mate Lucas di Grassi had to start lifting off the gas from the 28th lap to make sure of getting home.