The constantly changing Silverstone weather wasn't what Casey Stoner had hoped for in his quest to dial-out chatter from his RC213V - but he still finished Friday practice on top of the timesheets.

Last year's wet winner was fourth fastest in similar conditions this morning, then led the dry afternoon session by 0.034s despite only completing ten laps.

"We didn't learn very much from today," said Stoner, who start this weekend's British round 20-points behind Yamaha's Jorge Lorenzo. "In the first session we tried to understand the bike in the wet a little better, but it was gradually drying out throughout the session so it was difficult to take any real data.

"It was a similar situation this afternoon, we went out for a couple of laps and it started to rain which destroyed most of the session. We found the bike very hard to ride so we came in and made a change which took a lot of time and we didn't manage so many laps.

"It would be nice if we get some better weather again tomorrow and this wind makes things very tricky, but everyone is in the same position. The chatter is a little better, we made another small improvement but we'll need to check it tomorrow in some more consistent conditions."

Stoner and Repsol Honda team-mate Dani Pedrosa have to adjust to the new spec front Bridgestone slick this weekend, having previously opted for the now unavailable original spec.

Pedrosa, who missed last year's race due to a collarbone injury, spent Friday re-learning the lengthy Northamptonshire circuit and has plenty of tuning ahead to try and make the softer construction tyre work.

"It's been a tough day for me because it's a long time since I was here and it almost felt like a new track to me," said the Spaniard, currently third in the world championship. "I treated both practices as learning sessions, trying to learn the gears, the lines in the corners, the braking points and to find out the low grip areas.

"In the afternoon we used the new Bridgestone front tyre, the softer compound due to the cold conditions here, but we did just a few laps," he added.

"As I said in Barcelona we need to tune the set-up of the bike a little to work better with this tyre because for us it is too soft. Working with the weight distribution we might improve the performance".

Lorenzo was seventh fastest.