The Australians were just over a kilometre into their 4000m ride when Porter, riding at the rear of their four-man formation, had his shock equipment failure.

They were given a re-start and qualified fifth-fastest, meaning they are out of contention for the gold medal.

But they could ride off for the bronze, with the first round on Tuesday and the medals on Wednesday.

Porter's handlebars and stem came off the bike and he was lucky to walk away from the crash.

It was also fortunate for the Australians that Porter was at the rear of their pace line - if anyone had been behind him, they would have gone down as well.

He suffered a torn skinsuit and was furious as he walked back to the Australian team pits at Izu Velodrome.

The Australians were given a re-start after the medal round of the women's team sprint, less than half an hour after the crash, meaning they ended the day-one track program.

Despite face planting onto the track and sporting a nasty graze on his chin, among several other wounds, Porter rode in the re-start and lasted more than half the 4000m before pulling out of the paceline.

Porter, Kelland O'Brien, Sam Welsford and Leigh Howard clocked three minutes 48.448 seconds to be fifth-fastest, just behind Great Britain's 3:47.507.

World champions Denmark broke the Olympic record to qualifying fastest with 3:45.014.

Seven Network commentators Anna Meares and Scott McGrory, who between them won three Olympic track cycling gold medals, could not recall a similar crash.

It continued a tough start on Monday to the track cycling program for Australia, who were second-last in the women's team pursuit qualifying as Germany made a stunning statement.

The Germans broke the world record in team pursuit qualifying and also qualified fastest in the women's team sprint.

But China beat Germany for the women's team sprint gold medal, with the Netherlands taking the bronze.

Germany clocked four minutes 7.307 seconds in the team pursuit to beat the 4:10.236 that Great Britain clocked to win the gold medal at the Rio Olympics.

The British were on track to better the Germans' mark at 3000m, but faded to finish second-fastest in 4:09.022.

The Australian combination of Georgia Baker, Annette Edmondson, Ashlee Ankudinoff and Alexandra Manly rode 4:13:571 and are out of contention for the gold and silver medals.

They will face sixth-fastest team New Zealand in the first round and could progress to the bronze medal ride-off on Tuesday, but the Australians will need a big lift in performance.

Australia has never won an Olympic medal in the women's team pursuit.

Stephanie Morton's retirement means Australia did not enter the women's team sprint, which will be the only event to be decided on Monday.

Australian Associated Press