Tires are consumables. As soon as the wheels turn, they begin to wear. The speed of wear is related to many factors. The service life of the same tire varies depending on the road surface, load, driving technique, maintenance and maintenance level. Therefore, when the tire travels to a certain mileage, it should be replaced. Generally, the tire groove should not be less than 2mm, otherwise, it will cause side slip on the curve due to its poor grip, and there may be a dangerous accident such as a flat tire when driving at high speed. These are all related to the safety of the driver's life, so they should be highly valued.             

　　If the tires are to be roughly classified, they can be divided into tires with inner tubes and tires without tubes (usually called vacuum tires by car repairers). The principle of a tubeless tire is to save air inside the tube, and does not require precise contact between the tire and the rim. Even if the air pressure is low, there is no need to worry about the tires falling off the wheels, causing air leakage. Therefore, inner tube tires are commonly used in off-road vehicles and American street vehicles that use rims and steel wires. The principle of tubeless tires is to use the special structure of the rim of the steel ring (rim) and the edge of the tire to seal the air in the tire body. Even if this tire is stabbed by a foreign body, the air will not disappear immediately, and the repair of the flat tire is also very convenient, so it is very popular with Moyou. In recent years, tubeless tires have also been gradually used in ordinary motorcycles. It can be seen that the two types of tires have their own advantages.

　　Generally, qualified tires are marked with specifications, maximum load, inflation internal pressure, standard rim and trademark factory name and direction. If the tire is marked with specifications 90 / 90-18 51S, the first 90 means the width is 90mm; the 90 after "/" means the flatness ratio (%), that is, the height is 90% of the width; 18 indicates that the inner diameter of the tire is 18 inches (1 inch = 2.54cm),

　　Some tires are not marked with an aspect ratio, which means that the aspect ratio is 100%, that is, the width is equal to the height *.