Jenson Button admits McLaren must find a way to extract more performance from the hard tyres in use at Barcelona in time for Sunday\'s race after struggling on the compound in Friday practice. Although the former World Champion ultimately set the day one pace at the Circuit de Catalunya in the new-look McLaren with a strong lap on the faster soft compound tyres mid-way through Practice Two, in the early stages of the afternoon session he was heard complaining over the radio of understeer on the more durable \'prime\' compound. Button spoke on Thursday of the difficulty in consistently exploiting the full potential of Pirelli\'s tyres so far this season and on Friday afternoon reiterated that view, particularly with regards to the hard compound. \"It was a good afternoon,\" he told Sky Sports News after lapping 0.164s faster than Red Bull\'s Sebastian Vettel. \"But still I think a tough afternoon still trying to understand the tyres - and still don\'t quite understand them. \"The car seems to be working pretty well on the softer of the two tyres, but on the hard tyre I just can\'t get it working.\" Despite the sweltering track conditions in Barcelona, Button confessed that McLaren had struggled to get the silver-banded tyres up to operating temperature. \"I just can\'t get the temperature into the tyres,\" the 32-year-old added. \"I don\'t know why that is but it\'s something to sort out for Sunday.\"