Keiran McKandie, 16, from Elgin, died at the scene of the crash involving a white Volkswagen Golf on the B9010 Forres to Kellas Road on Sunday.
Relatives said in a statement: "Our darling, beautiful son was the love of our lives and the reason for living.
"Keiran lived, breathed, slept and dreamt downhill mountain biking - it was his world."
The statement added: "He was our only child, a devoted grandson, nephew, cousin and friend to many. Always forever in our hearts and he will never leave us.
"Even while he was eating his breakfast, he would be searching for biking videos on the internet.
"He loved all his biking buddies and shredding the tracks, and he was at his happiest when he was biking.
"Keiran was hard-working, genuine, caring, kind, loving, had a witty sense of humour and was ill tricked. He touched the hearts of everyone that was lucky to know him.
"Keiran will be forever missed by all his family, and his friends at Elgin Academy and the biking community. He had been looking forward to going on holiday with eight of his friends in the school holidays."
They added: "As a family we would like to thank the emergency services and all that attended and tried their very best to save him. We would also like to express our sincere gratitude to them at this horrific time."
A teenage cyclist killed in a crash "lived, breathed, slept and dreamt" mountain biking, his family has said.