Marcos Ambrose has broken his public silence on the shock decision to step down from full-time driving at DJR Team Penske ahead of his home event at Symmons Plains.

The 38-year-old has cited a variety of factors for the decision, which shocked his team and the wider V8 Supercars community when it was announced last week.

Ambrose will be at Symmons Plains this weekend working with his replacement Scott Pye, who has been charged with helping the team’s technical direction.

Having returned from nine years in NASCAR, Ambrose feels his own adjustment process is slowing the new DJR Team Penske alliance’s development to an unacceptable degree.

“It was a combination of a lot of factors,” Ambrose told V8 Supercars’ media partner News Ltd.

“It became obvious to me that returning to be the lead driver in this one-car team, and trying to improve the car — ultimately by race results and also by engineering the car — was harder than I had expected.

“So the duty on my shoulders, as a relative rookie in a series that has moved on, was to improve the racecar and the results.

“When it became obvious I couldn’t do that … it became an untenable position on me personally.”

Stay tuned to Speedcafe.com for the full story on Ambrose’s decision, including an extensive interview, to be published later this morning.