Supercars drivers fear a hairy qualifying for the Sandown 500, with a borderline track surface and wet weather forecast creating a wild situation.
Track records fell on Friday at the Melbourne circuit, which seven-times champion Jamie Whincup said was "radically different" from his previous visits.
A thunderstorm, up to 10mm of rain and potential hail on a cold day present a huge challenge for the field on Saturday as they gear up for the first endurance event of the season.
Track owners Melbourne Racing Club made adjustments to the track to ensure its preparedness for the weekend, including additional safety measures at the notorious turn six.
The use of resin to seal problem spots this week allowed Paul Dumbrell to set a new race lap record on during Friday's practice.
By the end of three sessions, resin was populating the track surface, leading Whincup to air his concerns.
"Days of research have gone on between the engineers behind the scenes to get ready to roll out on Friday then they decided to seal the cracks two days before the event," Whincup said.
"It's the biggest event that's here at Sandown.
"It's a little bit frustrating but it is what it is ... we've got to be a little bit careful.
"The sensible thing to do would be to throw the safety car out early if its wet and see."
Whincup was the quickest of the regular drivers, meaning his Triple Eight ZB Commodore is the car to beat.
Series leader Shane van Gisbergen also suggested Saturday could be wet and wild.
"The challenge is going to be tomorrow. If the grip goes away ... we don't know what the surface is going to be like with rain on it," he said.
"Basically it's just rubber which is slippery when wet.
"But we'll put wets on and deal with it."
Qualifying for the long-distance race takes place on Saturday and Sunday's race starts at 1.20pm (AEST).