He limped car #88 back to the pits and returned to the circuit to ultimately finish 19th.
“Broken brake bias cable,” Whincup told Speedcafe.com when asked of the cause.
“The bias went all the way to the rear and I was locking rears, overheated the rear tyres, and then they blew out.”
The six-time champion is unsure of the cause of the cable breakage, but lamented his poor luck after being set for another strong result to back up his second place finish in Race 3.
“We were on for the win,” said the 34-year-old.
“We'd done a good job, solid over the four races, and we were box seat for the win until the brake bias cable broke and that's the way it goes.
“We were competitive but unfortunately luck didn't go our way, which is disappointing.”
Meanwhile, DJR Team Penske is yet to determine the cause of the issue for the #12 Shell V-Power Falcon.
Coulthard said he had no warning when the tyre let go while leading.
“I hit the brake pedal and at the same time I had an issue with the left front tyre. There was absolutely no warning,” said Coulthard.
Dunlop has confirmed to Speedcafe.com that it will investigate the cause of the Coulthard blow-out.
The Virgin Australia Supercars Championship continues at the Tyrepower Tasmania SuperSprint from April 7-9.