The Sixty-Six Add-on for Trials Rising has 8 achievements worth 125 gamerscore.
Beat all the Stadium Finals in Sixty Six
Get a gold medal or better in all the career tracks from Sixty Six, including extreme tracks
Get your first diamond medal on any Sixty Six track
Find 14 squirrel collectibles in Sixty Six tracks
Travel to a different reality in "Ghost Town"
Navigate the underground caves of "The Petrified Forest"
Brave the burning building in "The Windy City"
Travel 15 miles through the Sixty Six tracks