The matter has been raised in both the Supercars and Super2 paddocks since track action kicked off yesterday, with some teams adamant the pre-marked hard compound tyres are quicker than the event-marked batch.
It's thought that Zak Best used a set of pre-marked tyres to take pole position for Super2 earlier today, while it is understood a significant amount of running was completed on the yellow-walled tyres, including Garth Tander's 2m04.135s, the fastest time of the weekend so far.
This is the second time this year that tyre batches have been an issue, after Best took a sensational main game pole at The Bend during his wildcard appearance on a different batch of tyres to most of the field.
In this case, however, there won't be an advantage in competitive sessions, given all pre-marked tyres must be returned to Dunlop ahead of qualifying.
Slick tyre pace is also unlikely to play a role throughout qualifying today or the Top 10 Shootout tomorrow given forecasts of heavy rain.
Dunlop has already increased its event allocation of wet tyres from five sets to six sets per car due to expected rain.
As it stands, however, all three practice sessions have taken place in mostly dry conditions.
