• Amanda Reid is hoping for gold in Tokyo, but has already won the hearts of fans at home. (AAP)Source: AAP
The Guringai and Wemba Wemba woman was the only cyclist to go under 39 seconds.

Amanda Reid has broken her own world record to win Australia's third track cycling Paralympic gold medal.

The 25-year-old clocked 38.487 seconds on Friday morning to win the C1-3 500m time trial at the Izu Velodrome and was the only rider to go under 39 seconds.

The Rio Games silver medallist, broke the 38.918 world record for the C2 class she set last November at Brisbane's Anna Meares Velodrome.

Reid, who has cerebral palsy and an intellectual impairment, swam at the London Paralympics.

But in 2015, Reid was jaded and she said a clean-up at home spurred her to change sports.

"I found my old cycling jersey from when I was little," Reid said.

"And I'm like, well, let's give this a go again, because I wasn't enjoying swimming anymore, so that's sort of how I got back into the sport."

At Rio, Reid won silver on the track in the 500m time trial and is the favourite in Tokyo, having reduced her own world record to 38.918 seconds in December.

But the Paralympics routinely throws up surprise results.

"You can never go in saying you're the favourite because you never know what everybody else has done," she said.

"You just have to go in and do your best."

While Reid is careful not to talk up her medal hopes, the Izu Velodrome was a happy hunting ground for world records during the Olympics and she wants to join that party.

"I'm hoping to break my mark again, that would be nice," she said.

"I've done the training so hopefully the training will pay off."

But Reid's switch from cycling to swimming hasn't all been success and speed.

Three years ago, she was accused in the media of exaggerating her symptoms.

The Australian Paralympic Committee, now Paralympics Australia, strongly backed Reid at the time, saying she has "multiple impairments".

"It's best to leave the classifying system up to the classifiers," Reid said this week.

Reid breaking cycling barriers
The Gurinagi & Wamba Wamba woman is a rarity in her sport, but wants to encourage more mob to join her in the elite ranks.