To unlock the given bike, complete all of the listed tasks.

Bike	How to unlock
Acrobatic Bike	Race 100% wheely and get 3 stars; do 2 front flips and get 3 stars; do 4 black flips and get 3 stars.
Bronze Bike	Get 24 stars in first three areas (Desert, Arctic, Dunes); win 3 consecutive races.
Ghost Bike	Play with 20 Facebook friends.
Girl Bike	Get 12 stars; do a backflip and get 3 stars.
Gold Bike	Earn 24 stars each in Desert 2 and Arctic 2; win 12 consecutive races; win 5000 games in multiplayer; beat a Silver Bike in multiplayer.
High Tech Bike	Create a game with a Facebook friend, with a random user, via SMS, and via email.
Hog Bike	Beat a Ninja Bike, a Ghost Bike, a Police Bike, and a Super Bike in multiplayer.
Ninja Bike	Win 250 multiplayer games.
Police Bike	Play with 5 Facebook friends.
Retro Bike	Win 5 games on multiplayer; Like Bike Race Page; Like Top Free Games Page.
Silver Bike	Get 24 stars each on Hills, Beach, and Savana; win 7 consecutive races; beat a Bronze Bike in multiplayer.