Wind. whipping at your hair which writhes alive as your two narrow wheels catapult down & down the grainy earth in loose clouds of dust while you turn corners, trusting rubber treads to cleave to the trail as gravity changes direction.
It's a steep, slick path and all you hear is Wind and all you feel is Wind and it's like you're standing still with an avalanche of trees and rocks and time crashing past your line of vision as if planet earth suddenly discovered it could fly and at that moment you discovered the perfect vantage point.