求翻译：教练车的调整与维护会影响到发动机的性能与汽车行驶阻力。例如一般驾驶员常用滑行距离来检查底盘的技术状况。当教练车的前轮定位正确、制动器摩擦片与制动鼓有正常间隙、轮胎气压正常、各相对运动零件表面光洁、间隙恰当并充分润滑时，底盘的行驶阻力减小，滑动距离大大增加。是什么意思？

Adjustment and maintenance of the coach cars will affect the performance of the engine and the car resistance. For example driver common gliding distance in General to check the technical condition of the chassis. When coach cars front wheels positioned correctly, brake drums and brake clearance, normally the relative motion of the parts of the tire pressure is normal, when appropriate and adequate lubrication of smooth surface, clearance, chassis reduce driving resistance, sliding distance has increased considerably.