I found the best and easiest way to get this achievement !
In Career go to the artic open event (second one in the row ).
In here select the Big air skill game.
Right at the start when the ramp starts going down lean you guy forward and bailout and the bike schould roll over you getting you the achievement.
This schould take you few tries only (i got run over 4 out of 10 times doing this )
Good luck and i hope it helps some of you guyz out :)