Here are the 360 Achievements that can be unlocked by completing the tasks below, the pts after the - sign is the amount of points you earn for each:

Challenge Expert - 30 pts
50 challenges completed

Challenge Master - 60 pts
All challenges completed

Extreme Bike Collector - 50 pts
Purchase all extreme bikes

GP Champion - 60 pts
Win career mode grand prix season on champion difficulty

GP Professional - 30 pts
Win a career mode grand prix season on pro difficulty

GP Legend - 100 pts
Win a career mode grand prix season on legend difficulty

Seeded #1 - 75 pts
Seed #1 achieved

Seeded #10 - 50 pts
Seed #10 achieved

Seeded #25 - 30 pts
Seed #25 achieved

Seeded #50 - 20 pts
Seed #50 achieved

Seeded #75 - 15 pts
Seed #75 achieved

Seeded #90 - 10 pts
Seed #90 achieved

Stunt Mode Rider - 10 pts
Win a Stunt Mode game in any multiplayer mode

Extreme Mode Champion - 10 pts
Win any extreme mode championship at any difficulty

Extreme 1000 - Legend - 60 pts
Win a career mode extreme 1000 season on legend difficulty

Extreme 1200 - Champion - 50 pts
Win a career mode extreme 1200 season on champion difficulty

Extreme 1200 - Legend - 75 pts
Win a career mode extreme 1200 season on legend difficulty

Extreme 1200 - Professional - 25 pts
Win a career mode extreme 1200 season on pro difficulty

Extreme 600 - Legend - 30 pts
Win a career mode extreme 600 season on legend difficulty

Accredited - 100 pts
All rider credits awarded

GP Rookie - 10 pts
Win a career mode grand prix season on rookie difficulty

50 Races (50)
Play 50 races online or offline.