The Holden Racing Team (HRT) withdrew their No.2 Commodore from the Great Race following the incident with veteran Craig Lowndes in Saturday morning's session.

"Unfortunately due to the damage to our car we will be unable to start the race," co-driver Luff tweeted.

"Absolutely gutted for the team, they have worked so hard all week. Once again if want to thank everyone for their support and concern."

Luff was behind the wheel when his brakes failed upon entering turn two on the Mount Panorama circuit - throwing the car sideways, into the tyre barrier and onto its roof.

Luff clipped Lowndes' Red Bull Racing Commodore on the way, sending the veteran into the concrete wall and destroying the rear of the car.

Lowndes emerged unscathed and immediately ran over to Luff to help him out of the wreckage, before the pair embraced on track.

"I'm fine, just obviously very disappointed for the team and obviously for Craig and those guys up the road," Luff said after the incident.

"Big thanks to Craig for helping me get out of the car, that was great."

Luff said he floored his brake pedal heading into the corner, but the car wouldn't stop.

"Something happened," he added.

"I'm not 100 per cent sure what, obviously the guys need to ascertain what's gone wrong."

Lowndes and Luff were co-drivers at Red Bull last year, winning the Enduro Cup with podium finishes at Sandown, Bathurst and Gold Coast.

Luff was later dropped by the team to make way for Steven Richards - who won the 2013 1000km classic with Ford Performance Racing's Mark Winterbottom.

The two Commodores had been among the frontrunners to take out the Great Race and were due to fight for pole position in Saturday afternoon's Top 10 shootout.

Tander and Luff's exit, however, opens the door for their HRT teammates James Courtney and Greg Murphy to take their spot in the shootout.

Lowndes and Richards have all but been ruled out of the one-lap qualifier but Red Bull are quietly confident of being ready for Sunday's race.

The frighteningly fast mountain claimed two other victims during qualifying on Friday, with championship leader Jamie Whincup and FPR's David Reynolds both crashing.

Winterbottom was quickest in Saturday's sole practice session, followed by Volvo's Scott McLaughlin and Shane van Gisbergen of Holden. Whincup was 19th.

The top 10 grid positions will be determined from 5.10pm (AEDT).

AAP