Sepang star Sergio Perez endured a difficult start to the Chinese Grand Prix weekend after braking issues hampered him during Friday practice in Shanghai.

The Mexican goes into the weekend on a high after his fine second place finish in Malaysia but could only set the eleventh best time in the two sessions in China.

Although a solid fourth in the mixed conditions in FP1, Perez was unable to run as high up the order in FP2 as an issue under braking prevented him from pushing as much as he wanted.

Indeed, one major lock-up almost saw Perez run out of road and led to him flat-spotting a set of his Pirelli tyres.

"The balance of my car had actually been better in the first free practice session compared to the afternoon," he said. "I wasn't too happy in the second free practice. I had problems with the brakes, which didn't work the way they should, and I lost too much front tyre temperature on the back straight. It was too easy to lock the front.

"We need to improve the car's overall balance for qualifying. We have a bit of homework now, but we have gathered quite a good amount of data."

Sauber team-mate Kamui Kobayashi however was happier with his performance during the two sessions, with the Japanese driver ending the day with the seventh quickest time.

"We had a few minor issues to fix, but overall today's practice sessions went smoothly," he said. "Sometimes the visibility was a bit poor and this didn't help to predict where the track was and wasn't slippery. My car definitely felt better balanced in the afternoon's practice session than it did in the morning, and I believe we look okay here on this track.

"Of course there is still room for improvement in regard to the set-up. When we make our decisions for tomorrow we will not focus too much on today's track conditions, as we expect the temperatures to be a bit higher then."