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