Here is the full list of all 8 PIPE by BMX Streets achievements.
Make it to the top of the mountain
Land 6 different aerial tricks and 6 different grinds in a combo with using only one Manual or Nose Manual trick.
Land 3 different aerial tricks and 3 different grinds in a combo without using Manual or Nose Manual tricks.
Become one with the cone
Ride the chicken bike
Land a 6X Barspin on the PIPE level
Perform a Tire Ride
Land a 4X Whopper on the PIPE level