Why coupling can wear? In CVT, by arrangement like planets orbiting the sun, rotating teeth-stop-motion holding each other in order to get the gear stage one, two, three, or more simple and retreated again. It uses the 'umbrella' front-rear pulley (drive pulley and driven pulley) that spins and will furl each other, and connect with a belt. When 'low gear' or when a new run, the small drive pulley radius, while the large pulley driven. While the current 'high gear' is the opposite, so enlarging the radius of the drive pulley, driven pulley be smaller. Motion was detained by the clutch pulley is centered in the shoe or the coupling. The more frequently used, or even invited to the far or often uphill and carrying heavy loads, the sooner discharged precisely the coupling.