Sebastian Vettel set the fastest time of the final practice session ahead of qualifying for the Canadian Grand Prix, as a KERS problem kept Mark Webber from getting out on track.

10457 - Vettel on top as Webber hits trouble

Drivers were finally able to display their true pace using the super-soft tyres although a crash for Pedro de la Rosa did bring out the red flag at the end of the session. Vettel's time of 1:13.381 beat Fernando Alonso by 0.3s, with Nico Rosberg a further 0.2s back. Felipe Massa was fourth quickest ahead of the McLaren's of Jenson Button and Lewis Hamilton.

Webber was never in his car as a KERS problem left Red Bull having to take the RB7 apart to address a battery issue, but the problem proved terminal and he was put firmly on the back foot ahead of qualifying.

The Mercedes pair of Rosberg and Michael Schumacher were keen to make the most of the hour-long session as they attempted to find ways of preserving their rear tyres in race trim having shown impressive raw pace. Rosberg was the busiest man of the morning as he completed 29 laps.

The pace on the soft tyre was impressive, Rosberg and Vettel trading fastest times at the top with Vettel lowering the benchmark to a 1:14.162. Rosberg only managed to find 0.2s when putting on the super-soft tyres, a time which Alonso matched to the thousandth of a second. Later in the same run, Alonso finally went quicker by 0.2s, before Vettel also set the fastest time after a number of laps showing that the option tyre can deliver sustained performance.

After three red flags yesterday it was almost inevitable another would be forthcoming, and so it proved right at the end when de la Rosa lost the rear of his Sauber on the exit of turn four, hitting the wall with the right rear before spinning across the track. After Kamui Kobayashi required a new chassis overnight an already busy weekend for the team got a lot harder as they work to repair the car in time for qualifying.

Lewis Hamilton was one of many to outbrake themselves in to a chicane, bouncing across the grass at turn four, while Rubens Barrichello also went off at turn nine and Jaime Alguersuari went very deep under braking for turn eight and had to take a trip through the gravel.

The work done this morning could prove to be redundant, however, as dark clouds gathered around the circuit late on. Rain is expected and the teams could find themselves doing their first competitive laps on the wet Pirelli tyres in this afternoon's qualifying session.