A man says he was terrified when his car windscreen was smashed in a road-rage attack involving a group of men on monkey bikes in Melbourne's west.

Brenton Davey, 31, said he was harassed by four men at the intersection of Ballarat Road and McIntyre Road in Sunshine about 10:00pm on Thursday.

He said the men on the low-powered motorcycles cut in front of him, were blocking lanes and riding erratically.

"I blasted my horn at them, as you do when there are people being idiots around you," he told 774 ABC Melbourne.

"I pulled up at the next set of traffic lights ... The one who was a pillion passenger got off the bike and proceeded to attempt to get into my car through the passenger door, which was locked luckily.

"He's then continued to punch at the window, kicking at the door, spitting at the glass then broke the driver's side mirror, then went back round to the front of the car and punched the windscreen, breaking that."

Mr Davey said when the traffic lights changed, the men drove off.

"I was terrified. The aggression he was showing, he was really acting crazy," he said.

"You can see the blood mark on it [the windscreen] where he's impacted. That's come directly off his hand.

"Even thinking back on it leaves me shaking."

Mr Davey drove to the nearby Sunshine police station to report the damage.

He described the man who punched his windscreen as Caucasian, of average height and dark hair, wearing a white T-shirt and dark pants.

All the men are thought to be in their late teens or early 20s.

Police have urged anyone who witnessed the incident to contact Crime Stoppers.