McLaren's Jenson Button confused by tyres in Spain

McLaren's Jenson Button is pleased after setting the best time of the day in second practice for the Spanish Grand Prix, but says he is still trying to understand the tyres.

The Englishman was 0.164 seconds ahead of world champion Sebastian Vettel at the Circuit de Catalunya in Barcelona.

Button says if he can resolve his problems with the harder prime tyres, McLaren can be "competitive" this weekend.

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