V8 Supercar Series leader Jamie Whincup had to settle for the sixth quickest time on the opening day of practice at the Falken Tasmania Challenge at Launceston's Symmons Plains Raceway on Friday.

Whincup was out of the top ten for much of the day and admitted that despite experimenting with the set-up, it still wasn't quite right.

"I had a relatively tough day today. We made a few little errors at the start of practice which put us behind the eight ball for most of the session," explained the TeamVodafone man.

"We also had some mixed weather conditions which interrupted our practice plans a bit. Not wanting to waste laps I sat out when it was raining while Craig had a run on wet tyres so we know what to expect if we do get wet weather tomorrow.

"It is just so close around here that I honestly think pole is going to go to the person who wants it the most. I will though be on my game tomorrow."

Craig Lowndes meanwhile was a lot more competitive in the sister car and the three-time champion was on the pace from the moment he hit the track.

After recording the fastest time in the second practice session, Lowndes also sat atop the timesheets right up until the last minute of the final session when he was piped by Mark Winterbottom.

"We had a pretty good day," Lowndes added ahead of what will be his 150th V8 Supercar start. "We had a list of changes we wanted to try and one of those changes gave us a good direction early on.

"We had a run in the wet, then sat it out while we waited for the track to dry as we didn't want to use up too many laps.

"The car is smooth and precise which will give us a really nice race car but the disappointing aspect was that we didn't really make the gains on new tyres like we thought we would."