Ducati's Valentino was unable to go for an outright laptime at the end of this afternoon's second MotoGP free practice session as chatter from the soft Bridgestone meant a planned run of laps was brought to a halt early on.

The Doctor had scheduled in time to spend evaluating the white-striped front tyre but said that a changed setting had invoked the vibration and he had to switch plans. He did, however, continue to use the harder rear but didn't get to stick in quick lap at the end.

"This afternoon we have some problem as the plan was to do the long run for Bridgestone but I had a lot of chatter, so unfortunately I have to stop and change the plan of the practice but I use all the practice the same rear tyre. We did more than 20 laps and fastest lap at the end so I think for Sunday we won't have particular problems from the rear tyres. Maybe the setting with the fork is the cause because we modify the setting and the chattering disappear with the same tyre, so maybe not the tyre, the setting," said Rossi, speaking to bikesportnews.com this evening.

"We are a bit more behind than what we expected because the other guys at the end put the soft tyre and they are able to improve a lot their laptime. We decided to continue to work on the hard because we lost some time at the beginning with this problem. At the end we don't know exactly what the potential with the soft. We can discover tomorrow in the qualifying.

"We have some problems to fix, especially in the second half of the lap. I lose a bit too much in some places so we have to modify something for tomorrow and then understand the potential with the soft for qualifying for try to start more in front. Our pace is not fantastic but not so far from the guys in front. We just two or three tenths for stay together so that is the target tomorrow."