Here's what you need to do (note these are subject to change, refer to the game for any changes). :)
  • The Micro: Unlocked by default
  • The Monster: Complete City Stage 3 in under 1:11
  • The Joyrider: Complete City Stage 3 in The Monster in under 0:59
  • The Classic: Complete CIty: Marathon in under 3:20
  • The Buggy: Complete Snow Stage 4
  • The Big Rig: Complete Desert Stage 4 in under 1:36
  • The APC: Complete Desert: Marathon
  • The Tank: Complete Snow: marathon
  • The Bouncer: Complete Snow Pro Racers 1 in under 0:57
  • The Lowrider: Complete City: Pro Racers 1 in under 1:07
  • The Trophy Truck: Complete Snow Big Air in the APC in under 1:15
  • The Racer: Complete Snow Rush in the Tank in under 0:55
  • The Beast: Complete Volcano: Marathon in The Trophy Truck in under 2:50