The apparently innocent victim was wearing a video camera on his helmet when he came across a slower rider on the popular Flying Nun trail on Christchurch's Port Hills.
The dramatic footage shows 24-year-old Jordan Brizzell asking the slower man to move to the side of the path and let him pass.
An extended version of the video depicts the man saying Mr Brizzell can pass while refusing to make room for him.
"He was holding me up pretty badly,'' said IT systems administrator Mr Brizzell.
"Trail etiquette says you pull over to let faster riders by. He kept saying yes but wouldn't give me a space. There were plenty of spots for him to pull over but he wouldn't.''
When asked again, the slower rider, wearing a yellow Rock Shox Racing top and tinted sunglasses, gets off his bike and confronts Mr Brizzell, saying he "doesn't need a f****** lecture while I'm enjoying a ride''.
The man appears to knock the faster rider to the ground, where a struggle ensues.
"On the longer version (of the video) you see that we collide at one point when I try to pass him, but he carries on.
"At the end of the track I told him he was rude for not letting me past, that set him off,'' the shaken-up Mr Brizzell says.
"He just went berserk, he lost total control. It was quite scary. When we were on the ground he said he was going to kick my head in, and that's when I started to yell.
"You can see how it unfolded in the video. He tried to strangle me with my helmet while he was trying to steal my camera, and when I started yelling for help he put his hand over my nose and mouth.
"I was getting pretty fearful for my life by that stage so I did the only thing I could do without letting go of the camera, bit down on his finger. That got his hand away.
"After a bit more struggling I managed to get up to the road where I yelled for help, another cyclist came over. The assailant started saying I was assaulting him, and the cyclist seemed to be taking his side. I got my stuff and got the f*** outta there.''
Mr Brizzell, who was cycling alone, says he phoned the police and gave a statement at Christchurch central police station on the incident which happened at around 4.40pm yesterday.
He claims that his alleged attacker later approached him in a car-park and asked him to delete the files from his video camera, but Brizzell refused.
"He kind of apologised then, but I think he was just hoping that I would delete the film.
"I tried to grab it off me, but I took a step back and another cyclist who was there told him to p*** off and he went away.''
Mr Brizzell, who lives in Christchurch, says he posted the video online to try to identify his alleged assailant.
The video, uploaded on You Tube yesterday has already received more than 2,500 hits and prompted dozens of comments.
One poster writes on TradeMe: "Wow!!! Crazy stuff. I'm sure he will be identified.''
Another posted: "I found that so distressing, gross over reaction to something, hope your ok.''
Mr Brizzell said this afternoon that one person had offered the identity of his alleged attacker.
See the video here (Warning: strong language):
