When Richie Porte, Rohan Dennis and Jack Bobridge took out the top three places in the elite men's Road Nationals individual time trial on Thursday, the order might have surprised some, but the end result did not.

Dennis was long touted as the favourite for the 40.9-kilometre route down the Buninyong Mt Mercer Road, but it was Porte who prevailed by just seven seconds in bitter wind and constant rain in his first national time trial title.

The Tasmanian rallied from a slow opening 20 kilometres - in which he trailed Dennis by as much as 30 seconds - to finish in 51:50.86.

"To win this time trial against such a class field - it's fantastic," Porte said.

"It was a great course for me (and) I haven't done a good time trial on a course like this for a long time.

The result mirrors Porte's and Dennis' efforts in the 2014 World Time Trial championships, in which the pair finished fourth and fifth respectively.

The 29-year-old's victory at Buninyong, just days after his engagement, has capped off what he describes as a "brilliant" off-season after a poor 2014 marred by health issues.

"It looks like I'm back on top of it (my health) and what a great podium we've got," Porte said.

"I've put a lot of work on my time trial position and I'm absolutely thrilled to have this jersey riding over in Europe.

"I've trained brilliantly, I haven't been sick and you can count on one hand the amount of nights I've had drinking or letting the hair down.

"I'm focused and it's a big year for me this year - there's a lot of people questioning me and my ability but, for me this year, I've got some big goals (Giro d Italia) and it's a fantastic way to start it."

Dennis was left ruing his poor pacing after the race, and needed to lie down before addressing the media due to severe fatigue stemming from his 51:58.04 ride.

"I was starting to get a little bit light headed," he said.

"It was just a a little bit of over exertion and probably just the shock of going that deep.

"I think I probably went out a little bit too hard.

"I've got a little work to do on the pacing side of things."

Both Dennis (BMC) and Bobridge (Budget Forklifts) will make attempts at the world hour record in coming weeks.

Reigning World Under-23 Time Trial champion Campbell Flakemore (BMC) rode impressively to finish sixth in his first senior ITT, while fellow newcomer Damien Howson crossed in fifth.

Past champion Luke Durbridge crossed in fourth, reigning champion Michael Hepburn rode well to finish seventh, while triple World Champion Michael Rogers finished eighth.

Top ten positions

1. 4 Richie PORTE (TAS) AUS19850130 51:50.86

2. 7 Rohan DENNIS (SA) AUS19900528 51:58.04 +7.1

3. 10 Jack BOBRIDGE (SA) AUS19890713 52:17.68 +26.8

4. 8 Luke DURBRIDGE (WA) AUS19910409 53:02.06 +1:11.1

5. 11 Damien HOWSON (SA) AUS19920813 53:14.28 +1:23.4

6. 9 Campbell FLAKEMORE (TAS) AUS19920806 53:37.74 +1:46.8

7. 1 Michael HEPBURN (QLD) AUS19910817 53:55.75 +2:04.8

8. 6 Michael ROGERS (ACT) AUS19791220 54:16.05 +2:25.1

9. 50 Ben DYBALL (NSW) AUS19890420 54:18.79 +2:27.9

10. 35 Lachlan NORRIS (VIC) AUS19870121 54:24.94 +2:34.0