我往车后退了两步，妈妈深呼了一口气，将踏板踩到底部，就像我刚才教她的一样，慢慢地，自行车往前滚动了，沿着山坡往下，车的速度越来越快，前轮开始快速地晃动。
My mom took a deep breath and pushed down on the top pedal just the way I'd shown her. Slowly the bicycle rolled forward, picking up speed as it coasted down the hill.
同时，应进一步提高制动器的制造精度，从而限制踏板行程的“非正常”增长，满足双管路制动系统的使用要求。
Meanwhile, the manufacturing precision of the brake should be further improved to limit the non-nor-mal increase of braking pedal travel in order to meet the operation requirements.
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