Mercedes team boss Ross Brawn has said there is no guarantee the new Pirelli tyres will help Michael Schumacher in 2011.

Schumacher struggled during his F1 comeback last season and while he did finish the year on a relatively positive note, the German, who turned 42 this week, remained unhappy with the grip from the Bridgestone tyres.

Brawn is certain though that Schumacher will have a 'better time' this season, although he is not convinced the switch to Pirelli rubber will answer all of his problems.

"It's a little premature to say that," Brawn confirmed to Italian newspaper, La Gazzetta dello Sport.

"During the tests in Abu Dhabi we didn't see any big differences in performance compared with Bridgestone. But it is clear that in changing the supplier, the car will have to be different and there may be a lot of changes during the winter tests [too]."