Nick Heidfeld denied Lewis Hamilton a perfect practice ahead of Saturday`s qualifying for the Chinese Grand Prix.

Hamilton described Friday as one of his best of the year after topping the timesheets at the end of both 90-minute sessions.

In the final hour-long practice run at the Shanghai International Circuit and with the top teams running with considerably heavier fuel loads, Hamilton had to settle for second behind Heidfeld.

There was also one hair-raising moment for Hamilton at a time when he thought he had conquered his pit-lane demons.

Having just set the fastest lap midway through the session, the 23-year-old opted to return to the garage.

Last year during the race the pit-lane gravel trap proved his undoing as, on severely-worn tyres and a damp track, he slid off and beached his car, a moment that helped wreck his title hopes.

Hamilton mentioned yesterday after the two practice sessions he "went at it" on entry to "get rid of any bugs" he might have been carrying from last year.

On this occasion, Hamilton went in a little too hard as he missed the apex of the pit-lane bend and although he avoided the gravel, he was forced to use the exit road to the right.

After a nifty reverse manoeuvre and with tv cameras picking up what must have been a wry conversation with team principal Ron Dennis, Hamilton eventually made it back to the garage.

His eventual best time around the 5.451km track was one minute 36.135 seconds, just 0.074secs down on BMW Sauber's Heidfeld but half a second off his hottest lap from Friday.

Their team-mates in Robert Kubica, still in with a shout of the title as he trails Hamilton by 12 points, and Heikki Kovalainen, were third and fourth quickest respectively.

Toyota's Jarno Trulli and Nico Rosberg in his Williams were fifth and sixth with Sebastien Bourdais again performing well as the Frenchman finished seventh for Toro Rosso.

Red Bull's David Coulthard, Williams' Kazuki Nakajima and Nelson Piquet in his Renault completed the top 10.

Felipe Massa, five points behind Hamilton and Ferrari team-mate Kimi Raikkonen were a lowly 12th and 13th but unquestionably heavy on fuel.

Jenson Button was 15th for Honda with the Force India duo of Adrian Sutil and Giancarlo Fisichella again bringing up the rear, the latter almost two seconds down on Heidfeld.

Mark Webber's Red Bull team, meanwhile, face a race against time to prepare his car for qualifying after the Renault engine blew at the end of the long main straight 45 minutes into the session.