A video of a mountainbiker allegedly assaulting another Christchurch cyclist on a Port Hills track has gone viral online.

The incident was caught on film using a helmet video camera by mountainbiker Jordan Brizzell.

Brizzell, 24, said the incident began when he asked another cyclist to give him room to pass on the Flying Nun track on Sunday afternoon.

The man said "yes" but allegedly would not give Brizzell space to pass.

"Trail etiquette says you pull over to let faster riders by," Brizzell said.

He said he was polite at first but "got less polite as he refused to stop".

Brizzell told the man he was rude for not allowing him to pass, and "that set him off".

A scuffle ensued in the course of which "he put his hand over my nose and mouth", Brizzell said.

Brizzell said he "did the only thing I could do without letting go of the camera  bit down on his finger".

After "a bit more struggling", Brizzell said, he managed to get away.

"I rolled down the road and spoke to a couple other guys at the car park," he said.

"They said I should ring the police, so I got my phone out and that's when the guy showed up again, so that's when I took a photo."

Brizzell said he suffered bruising on his neck and jaw from where the helmet strap was pulled, along with sore neck muscles and grazes on his ankle and arm.

He posted the video online on Sunday to see if anyone could identify the man.

Most responses had been positive, but some people had tried to blame him for the incident, he said.

"I'll admit I didn't act in a textbook fashion and I have learnt from this, but I still don't think that anything I said or did was unreasonable or out of line," he said.

He had given a statement to the police and was waiting to receive more information.

"Nothing like this has happened to me before," he said.

- © Fairfax NZ News