Aussie breaks 'unbreakable' 4km record

Australia's Commonwealth champion Jack Bobridge smashed Christopher Boardman's individual pursuit world record, becoming the fastest cyclist over 4000 metres in history.

Bobridge, 21, broke the record set in 1996 by Britain's Christopher Boardman, riding a time of 4 minutes 10.534 seconds in his heat at the national titles on Wednesday.

The South Australian's new record took 0.58 of a second off Boardman's old time.

"I don't think it has really sunk in yet," Bobridge told reporters after retaining his national title in the event.

"Maybe tonight and when I relax a bit it will.

"But I couldn't let this morning's ride overwhelm me, I had to come out and ride the final still.

"So as much as I enjoyed it, I put it aside for a couple of hours so I could come out and try to take the win."

Boardman has already passed on his congratulations to the new world record holder, writing on Twitter, "Wow Jack Bobridge broke my 15yr old world record, 4:10.5 that is an amazing time, congratulations to him."