A cyclist has uploaded shocking road rage footage capturing the terrifying moment he was threatened by a knife-wielding driver - on a quiet Warnbro road in Perth's southern suburbs.

The video, posted online by a WA-based cyclist, shows a four-wheel-drive's attempts to get through a roundabout ahead of the bike, causing the pair to come within inches of each other.

The cyclist swerves, clipping the front of the vehicle, before shouting "what the f--- are you doing."

Moments later the driver speeds past the cyclist, who has cameras attached to both his helmet and bike, and can be seen in the distance pulling over.