Hamilton shows improved speed

World champion Lewis Hamilton put his McLaren team's troubles behind him by setting the quickest time in first practice for the Chinese Grand Prix ahead of compatriot Jenson Button on Friday.

The 24-year-old Briton, whose title defence has been marred by struggles on the track and controversy off it, swept around the 5.451km track in one minute, 37.334 seconds on a bright but breezy morning in Shanghai.

A day after his long-term mentor Ron Dennis severed ties with McLaren's racing team, Hamilton topped the time sheets with the 15th of his 22 laps at the circuit where he claimed his last victory in the penultimate race of the 2008 season.

Button, who is chasing a third straight win this weekend, was second quickest with a lap of 1.37.450, ahead of Brawn GP team mate Rubens Barrichello (1.37.566), a winner here for Ferrari in 2004.

The Brawns were expected to dominate the weekend after their rear diffuser was declared legal by the sport's governing body on Wednesday but Heikki Kovalainen proved his team mate Hamilton's time was no fluke by finishing fourth fastest in 1.37.672.

Australian Mark Webber continued Red Bull's good showing so far this season for fifth place but Toyota's Jarno Trulli and Nico Rosberg of Williams, both using the rear diffuser, will be disappointed to have finished six and seventh in the times.

Ferrari's travails continued, however, with Finn Kimi Raikkonen 11th fastest and Brazilian Felipe Massa managing only the 15th best time for the reigning constructors' champions.

Raikkonen was one of several drivers who came off the track as teams struggled with grip as they weighed their tyre choices for the weekend.

A second 90 minute practice session takes place later on Friday.