back turn pulley

例句：

1. 1. The car's back wheel is worn out, so I need to replace it.
   汽车的后轮磨损了，所以我需要更换它。
2. 2. The rear wheel of the bicycle is loose, causing the bike to wobble.
   自行车的后轮松动了，导致自行车摇摆。
3. 3. The rear pulley on the elevator is broken, which makes the elevator unstable.
   电梯的后轮装置坏了，使得电梯不稳定。