Casey Stoner has admitted struggling to solve a temperature issue with his rear Bridgestone tyre at the legendary Assen circuit in Holland today.
The Australian ended the opening practice session for Saturday’s Dutch TT in second place with a best time of 1.35.180.
That left the 2007 world champion just 0.011s behind runaway series leader Jorge Lorenzo but well clear of factory Ducati team-mate Nicky Hayden in third spot.
But the 24-year-old conceded he was plagued again by a tyre temperature issue that struck during last weekend’s British GP at Silverstone.
Conditions were unusually hot and humid at Assen today with track temperatures peaking at 44 degrees.
But Stoner said: “I felt more comfortable today. By race day at Silverstone I felt a lot better but I couldn’t show our potential and had some problems with the arm pump. Here we’ve got a little bit more feeling with the front-end but I’m struggling a little bit with rear grip now.
"By the end of the session we improved the rear grip but lost the turning so we have to find a balance. We just need to get a little more comfortable with the settings we’ve got and see what we’re capable of tomorrow. I’m struggling to get temperature in the tyre. We’re having the same issue with Silverstone on the left side of the tyre.
"Each time we exit the grip gets worse and the temperature gets lower. We’re running 80 degrees when we should be running one hundred. It is similar on the right side too so we’ve got to change some things to increase the temperature again.
"When we try and increase the temperature it changes the feeling of the bike and the way our bike likes to work. It is making things difficult for us at these past couple of weeks.”
Stoner said he was at a loss to explain the cause of the issue but he will try and remedy the problem by running a stiffer version of Ducati’s carbon fibre swingarm.
He added: “We’ve no explanation at the moment. I’m planning on doing a test tomorrow with the stiffer swingarm. We’ve tried a few things over the last weekend and today but we’re still struggling to get the tyre temperature up.
"It’s an issue I’ve had in the past but with the tyres that Bridgestone are giving us they seem to be running very hard compounds. The softer and the harder option have the same option on the left.”
Stoner also said he had an issue with former factory Ducati team-mate and experienced Italian Loris Capirossi during today’s session.
Capirossi apparently baulked Stoner and he said: “Twice he got in my way big time today. For such an experienced rider he looked behind and saw me coming but took his time to get out of my way.
"I was coming into the pits but he wasn’t and he wanted to follow but he was right on the racing line. When they shut off the gas in a fourth gear corner it is not the nicest thing. I was a little bit disappointed with Loris today.”