Daniel Ricciardo is confident his Red Bull is faster than the car he drove to third place in the Formula One drivers' championship last season.

Whether it's fast enough to catch the Mercedes entries, he says, only time will tell.

Ricciardo is back in Melbourne for Sunday's season-opening Australian Grand Prix, where F1 rule changes requiring wider tires, greater aerodynamics, bigger fuel loads and increased downforce are expected to make the heavier cars significantly faster than previous years.

Nico Rosberg won the Australian GP last year, and held off Mercedes teammate Lewis Hamilton for the 2016 title. Rosberg's retirement leaves Hamilton the favorite to win a fourth F1 championship.

Ricciardo is expected to again be among the leading contenders, and he's back on his home track feeling content with progress over the off-season. He placed fourth in Melbourne last year, but improved during the season and won the Malaysian GP, got his first pole position and picked up seven other podium finishes.

The 27-year-old Australian said winter testing at Red Bull, alongside teammate Max Verstappen, had been the best he'd been involved with. He said he was less than a half second behind the Mercedes.

"Testing is never really a clear picture. I expect Ferrari and Mercedes to be quick and I hope we can be with them as well," he said. "We're coming here pretty confident."

The newly developed F1 cars have tires which are 25 percent wider, have more grip and - crucially - are more durable, enabling drivers to push harder and limiting the cyclical pit stop strategy that made many races easy to call.

Ricciardo produced the fastest lap in the 2016 Australian GP and predicts his new Red Bull vehicle is 40 kph (25 mph) faster through corners.

"We've gone from 220 (137 mph) to 260 (162 mph), so that's a big difference and that's more fun for sure," he said. "I think as a spectator now when you're paying money to see a race and you see us corner at these speeds, you're getting more for your money as well."

Forecast rain may slow the cars down, though, with showers expected on Saturday for the qualifying and Sunday during the GP. The first practice sessions are set for Friday.

Australian race fans, who flock to the Albert Park street circuit in their tens of thousands, are hoping to see the Ricciardo's now famous Shoey, where he celebrates success by drinking from his racing boot.

Ricciardo is hoping there'll be plenty of Shoey shows in 2017, saying his aim is to be the world champion and he'll be doing everything he can to make it happen this year.