Here is the full list of all 35 Shredders achievements.
Complete 25 gaps
Unlock all the gear in the game
Play in a private session
Call the snowmobile 500 times
Collect 40 collectibles
Complete 10 gaps
Complete the AirBorne Mission
Complete the Cliff Drop Mission
Complete The Village Roof Run Mission
Complete the Canyon Jump Mission
Call the snowmobile 50 times
Jump over the Rugby pole at the park
Ride 10 km with the snowmobile
Rock the invitational!
Complete the We Own The Sky Mission
Complete The Lawn Darts Mission
Spin a total of 360.000
Complete The Dammed Mission
Complete the Hit The Streets Mission
Complete the Factory Worker Mission
Complete the Spin Dizzy Mission
Collect 10 collectibles
Bail 100 times
Jump 1000 times
Complete the Forest Cross Mission
Complete The Beat The Street Mission
Collect all the SHRED letters in a mission
Ride 10 km of deep snow
Ride 50 km
Complete the Fast As Hell Mission
Get a Score of over 6666 in a single trick
Land a 1080
Transfer 3 rails
Land a 540 Indy
Land a double backflip