Reigning Bathurst 1000 champion Chaz Mostert topped the sixth and final practice session ahead of a top-10 shootout expected to be decided in heavy rain at Mount Panorama.
In a sign of how quickly racing conditions changed on Saturday, Alex Hadden lost control in the Toyota 86 series competition following practice six and rolled his car into Bradi Owen, who came off the track before the penultimate corner of the circuit.
The track had dried out before the Toyotas went out but quickly turned into a water park, causing Hadden to spin into the sand and collect Owen's already strewn car.
Brave fans who had lined up for the Supercars drivers' autograph session remained under the downpour by pit paddock before the top 10 from Friday's opening qualifying duel for pole.
In the premier categories' final practice, it was Mostert who registered a 2:05.510 ahead of Shane van Gisbergen and Will Davison to go fastest.
The signs are ominous ahead of final qualifying with the rain much heavier than any other day at Mount Panorama.
All 56 drivers have braved wet, intermediate and dry conditions attempting to gauge the best set-ups for Sunday with the weather bureau forecasting more wet weather.
The Bathurst 1000 top-10 shootout begins at 5.05pm AEDT with Cam Waters last to drive after securing provisional pole on Friday.
