The quality of the trolley case is mainly judged from three aspects, namely the trolley, the wheel, the material of the fabric, etc. Therefore, as an important part of the trolley case, the choice of the trolley case is very important, so what are the characteristics of the trolley of the luggage?   What are the characteristics of the trolley case?   1. The material of the tie rod can generally be divided into all-iron tie-rod, all-aluminum tie-rod, and outer-iron inner-aluminum tie-rod. It is used more on medium and high-end bags.   2. According to the shape of the tie rod, it can be divided into square tube, oval tube, round tube, D-shaped tube, drum-shaped tube, striped tube, eight-shaped tube, ladder-shaped tube, mouth-shaped tube, fan-shaped tube, etc.;   3. From the position of the tie rod, there are built-in tie rods and external tie rods.The built-in pull rod is the pull rod inside the box, most of which are in the market, that is, the outside of the box is flat, and it seems that the two rods are stretched from the box. When you open the box, you can see or touch it through a layer of cloth. The kind with two sticking poles.   4. According to the length, the pull rod can be divided into 2 sections, 3 sections, 4 sections, and 5 sections. It depends on the size of the luggage. The 16-inch boarding box is generally 4 and 5 sections, and the 28-inch box is generally 2 sections.   Many customers who come to buy a trolley case have many misunderstandings about the shaking of the trolley. I don't know whether the shaking is good or not. Let me tell you why the trolley of the trolley case shakes: The shaking of the tie rod is scientific. The tie rod is composed of multiple sections and has a telescopic function. In order to ensure the smooth use of the tie rod under the phenomenon of thermal expansion and cold contraction, there must be a certain gap between each tie rod. The tie rod that does not shake has hidden dangers and small gap. , The friction force is relatively increased, the pull rod shrinks inflexibly, it is easy to get stuck, and the service life is affected! If the suitcase is bumped during transportation, the tie rod retains a certain gap to buffer the impact force, so that all the impact force will not impact on the tie rod, shortening the service life of the tie rod! But don't shake too much.   How to overhaul the universal wheel   1.Detect the visible wear degree of the tire tread. The "flat spot" on the tire tread can indicate the accumulation of foreign matter, such as wire and other debris that may wrap around the wheel, remove the bolts and nuts on the wheel, and clean the debris. Check whether the wheel bearing is damaged. If the parts are not damaged, you can reassemble and continue to use. If you often encounter the phenomenon that the wheel is entangled by sundries, it is recommended to install an anti-winding cover to avoid it.   2.The loose caster or the stuck wheel can also cause "smoothing point". Proper maintenance and inspection, especially checking the tightness of the bolts and the amount of lubricating oil, and replacing the damaged casters can enhance the rolling performance and flexible rotation of the equipment.   3. Severely damaged or loose rubber tires may lead to unstable rolling, air leakage, abnormal load, and damage to the bottom plate, etc. Timely replacement of damaged tires and bearings can reduce the cost of downtime due to caster damage.   4. After checking and repairing the wheel, determine whether the bolts and nuts are tightened. Use lock washers or lock nuts on all bolts as much as possible. If the bolts are loose, tighten them immediately. If the wheel installed in the bracket is loose, the wheel will be damaged or unable to turn.