Carapaz and Sloevnian Tadej Pogacar swapped the Tour de France podium for the dais in Tokyo where they were separated by silver medallist Wout van Aert from Belgium. 

Carapaz - who was third in this month's Tour de France - launched a late attack to ride solo to the line after 244km and win by 1min 07secs from van Aert and Pogacar, who is the reigning two-time Tour de France champion. 

Porte was 48th after more than 6hrs 15mins in the saddle while his Australian teammates Lucas Hamilton and Luke Durbridge were 71st and 72nd. 

"Obviously I'm disappointed that it went the way it did but riding with Luke Durbridge and Lucas Hamilton was brilliant, they did a super job for me and put me in a good position on the final climb but I didn't have the legs," Porte said. 

"It's disappointing, it's always nice to represent the country but when you have days like this it's not ideal. 

"It was one of those climbs where you either had the legs or you didn't, there was no hiding, it was 7km with 10 per cent (gradient) and with the heat it was one of the toughest days I've ever had on a bike. 

"Hopefully I can recover for Wednesday's time trial." 

An eight-man breakaway built a lead of over 13 minutes earlier in the race before the peloton began reeling it in with 128km remaining. 

Great Britain's former Tour de France champion Geraint Thomas was forced to abandon after a nasty crash, as was defending champion Greg van Avermaet from Belgium, while the race for gold heated up on the slopes of Mount Fuji. 

Pogacar launched an attack with 37km to go but it was the counter move from Carapaz and American Brandon McNulty which proved race defining. 

An emotional Durbridge said he was proud of the Australian team for giving its all. 

"I tried to give the guys the best chance, I knew my job would be getting as much food and nutrition to them as possible and I'm really proud of them, Richie coming off the Tour de France and Lucas off a crash and they both gave 100 per cent," Durbridge said. 

"I'm just really happy to be here, it gives me a lot of pride and I'm a bit emotional really." 

Hamilton said he was still coming to terms with making his Olympic and Tour de France debut in the past month after a brutal road race in Tokyo. 

"Solid way to start, a really hard day, the strongest guy won today, the humidity and course it was solid," Hamilton said. 

"It was only three of us and Durbo did a job for 10 men, and we did the best we could."