The main cause of fetal crown cut is the road obstruction, which has been laid in the road better, but often have such as nails, glass and other things, and always threaten the safety of tires. Another example has been introduced in front of the unit gate iron fence fixed on the ground, at the intersection of roadblocks fixed objects, the teeth on the road under the iron rack edges and corners, etc., are threatening the safety of tires. While the laying of the road or site and other places, fetal crown of the "natural enemies" are more. Such as stone, iron nails, steel, angle iron and other sharp objects, can be cut or stabbed fetal crown. Sometimes sharp objects will escape the tread on the pattern, directly cut fetal crown of the fetal base, the pressure of the middle part of the tread of the little stress, mainly by the shoulder on both sides of the ground, to shoulder on both sides of the shoulder soon Grinding, and the middle part of the crown but because the force is very small, the pattern is still very deep.