The practice pace-setters have played down the effect of Supercars’ centre of gravity adjustments despite Holden teams turning the tables on the opening day of the Tyrepower Tasmania SuperSprint.

While Ford Mustangs of Shell V-Power Racing’s Scott McLaughlin and Fabian Coulthard, and Tickford Racing’s Chaz Mostert, have accounted for all six race wins and all six Armor All Pole Positions to date, ZB Commodores filled the top five in Friday practice at Symmons Plains.

Jamie Whincup set the pace with a 50.5084s while Red Bull Holden Racing Team team-mate Shane van Gisbergen also went under the former’s old practice record.

Third through fifth on the timesheets was filled by Penrite Racing’s David Reynolds, Irwin Racing’s Mark Winterbottom, and Mobil 1 Mega Racing’s James Courtney, making for three different ZB chassis builders in the top five.

Despite the mandated movement of ballast to the top of the ZB Commodore and Ford Mustang since the Albert Park event, summing to 6.7kg and 28kg in the respective models, the fastest drivers at Symmons Plains claimed there was no discernible difference.

“I don’t think you’re going to notice six kilos around here; I don’t think centre of gravity’s a big thing,” said van Gisbergen.

“I’m 15 kilos heavier than Jamie and we’re pretty evenly matched every week, our car weighs the same in total, (but) I run a bit less lead, and we’re separated by nothing.

“I don’t think you’re going to get any answers this weekend; Phillip Island will be the real test.”

Whincup, who stated that he set his fastest lap on four new tyres but believed that others had used only two, suggested that difference in tyre freshness as well as considerations around the new parc ferme procedure meant that little could be read into the apparent form reversal.

He alluded to the possibility of aerodynamic disparity between the Mustang and rival models, which would not be apparent until the Virgin Australia Supercars Championship arrives at the wide, open Phillip Island Grand Prix Circuit next weekend.

“The biggest factor today is tyres,” he declared.

“It would have been fantastic if everyone had have run greens at the end there and we see who’s positioned where, but our main opposition chose to save tyres, so we don’t know their true performance.

“Another big factor is the parc ferme and they’re probably just running a race car (set-up), or they may not be, we just don’t know.

“But on top of all that, as SVG said, this is not an aero track at all. The true test is going to be at Phillip Island to see if we’re as even as we should be.”

McLaughlin similarly claimed to have not felt a difference in his Ford from its Albert Park state to that of Symmons Plains, where the extra weight has been wrapped around the top of the roll cage.

“I think on a test day, if we had put it in and back-to-backed it, I would have been able to say, ‘Yeah, it was the difference,’” he explained.

“But just jumping in the car today, I can’t 100 percent tell you this is completely different. It just looks ugly.”

The championship leader was seventh fastest in Practice 2, in which all but wildcard Jack Smith improved on their earlier efforts, but refuted suggestions that he had less favourable rubber than the likes of Whincup and van Gisbergen for his flyers.

“They’re talking shit,” claimed McLaughlin.

“I ran four (new) tyres; we just had a different warm up phase. What we did, we heated the lefts up, and then put the right sides on. But over the years I’ve tried a bit of both and my preference is probably four tyres. So might find a little bit of time in that too maybe, I don’t know.”

The field returns to the track for Practice 3 tomorrow at 1110 local time/AEDT.