Practice at the Chinese Grand Prix has caused some headaches for the teams and Pirelli after a number of left-rear failures for both Williams and Renault.
From Andrew Benson's race report for the BBC:
Felipe Massa suffered two left-rear tyre failures and Kevin Magnussen a left-rear problem on his Renault. Both were using the 'soft' Pirelli tyre.
Pirelli said the Williams failures were not punctures but "technical trouble".
Pirelli said investigations into Magnussen's problem were still ongoing. The Dane's left-rear suspension failed and he had a puncture but it is not clear which was the initial cause of the problem.
Rosberg meanwhile topped the times in the final moments of FP1 taking the edge over Hamilton who had a number of spins himself and will cop a five-place grid penalty for qualifying after a gearbox change.