Beat the Heroes Story Mode to get Storm's Missions and The Babylonian Story.
Beat Babylonian Story to get Wave's missions.
Get 50 points on the Heroes and Babylonian Prix and beat Wave's and Storm's missions to get Jet's missions.
Beat both Team Rose and Dark missions to unlock
Get all gold medals on all missions By Hunter Ho
you have to complete all Storm and Wave missions with any rank
You have to complete the Team Heroes and Team Babylon missions to unlock Shadow and Rouge.
Impossible to obtain Super Sonic without getting Gold rank in all missions.
Complete all missions to unlock Ulala, Aiai and Nights. For Sonic Riders: Zero Gravity, complete all missions to unlock Nights, Amigo and I think Billy Hatcher, I have them unlocked I just haven't played the game in ages.
Same with NiGHTS and Billy Hatcher. Complete all the missions
You have to defeat all story missions in team heros and team Babylon.
You are supposed to get all gold medals on Storm's and Wave's missions. You will unlock NiGHTS, AIAI, and you will get the Emerald Board, which in if you are Sonic while riding the board, you will transform into Super Sonic, and go faster than ever!Complete all missions regardless of rankings.
You can't but if you get all extreme ranks on all missions then you can unlock him (it is only usable by sonic) By Hunter Ho
to unlock it you need to beat all of storms missions and waves and unlock the 2 carnivals (day,night)
Silver is not in Sonic Riders. However, he is unlockable in Sonic Riders: Zero Gravity by completing the Babylon story.