SEPANG, Malaysia (Reuters) - Pirelli defended their tyres on Friday after Formula One champion Sebastian Vettel and Red Bull team mate Mark Webber said tyre wear was becoming too dominant a factor in racing this season.

Red Bull Formula One driver Sebastian Vettel of Germany stretches as he watches the first practice session of the Malaysian F1 Grand Prix at Sepang International Circuit outside Kuala Lumpur, March 22, 2013. REUTERS/Edgar Su

"The whole category is geared around tyres at the moment," Webber fumed despite topping the timesheets in the morning session ahead of Kimi Raikkonen's Lotus.

"Everything is around tyres. Tyres, tyres, tyre, tyres, tyres," the Australian added, while noting the wet track following a downpour in the second session was "the only conditions the slicks work in".

The Red Bulls locked up the front row in last week's season-opener in Melbourne but their one-lap speed was negated by tyre degradation in long runs as Raikkonen took full advantage to romp to victory.

Vettel dropped from pole to third at Albert Park and, while the German clocked the second fastest time of the day in Sepang on Friday behind Raikkonen, the triple world champion was less than enthused by his own battle with the Pirellis.

"It looked pretty okay but it was quite a mess if you look at how long the tyres lasted," said Vettel, who complained over his team radio that the car was vibrating badly after 16 laps on the hard tyres in the morning.

"Today, tyre wear was pretty severe for everyone, so obviously you drive way under the potential of the car.

"I hope we have enough tyres to survive the race and it is not a lot of fun and that is how it is."

Pirelli motorsport director Paul Hembery reacted by saying the tyre wear experienced at Sepang was within the expected limits.

"As we expected, we saw quite a high wear rate today, due to the more extreme nature of our 2013 tyres as well as the high temperatures and abrasive track surface," Hembery said.

"Nonetheless, degradation stayed within our anticipated parameters."

Pirelli have changed the tyre compounds for this season to try and ensure more pitstops during races and enliven strategy.

"We have also seen differences in the way that individual teams use the compounds, with the hard compound lasting 15 laps for some teams and 21 laps or more for others," said Hembery.

"We'll be looking at all the data tonight to establish a more precise picture for qualifying and the race."

(Editing by Patrick Johnston and Alan Baldwin)

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