Here is the full list of all 12 Smash Cars achievements.
Get 30 stars in one level. You must earn a bronze medal or higher in order to unlock the trophy.
Hit 15 objects in any level. You must earn a bronze medal or higher in order to unlock the trophy.
Earn a bronze medal, or better, in every level.
Earn a silver medal, or better, in every level.
Earn a gold medal in every level.
Get 75 seconds of air in any level. You must earn a bronze medal or higher in order to unlock the trophy.
Accumulate 270 stars using your best score from each level.
Complete 15 air tricks in any level. You must earn a bronze medal or higher in order to unlock the trophy.
Beat all base lap times in every level.
Beat all base race times in every level.
Find all the shortcuts in every level.
Complete all levels without crashing or using any respawns.