Bicycle tire specifications 559, 571, 584, 590. 
1. 53-559 units of bicycle tire specifications are millimeters, meaning that the tire width is 53 millimeters and the rim diameter is 559 millimeters.  26*1.95 is an Inch unit, meaning the wheel diameter is approximately 26 inches, and the tire width is 1.95 inches. 26 is available in a variety of sizes, including 559, 571, 584, 590, etc. Mountain bikes are generally 559, commuter cars are 590 and 571, and the 650C road car is also 571. 
2, the function of the outer tube is to protect the inner tube from injury, according to the grain on the outer tube to judge the cross-country tire or snow tire.  Cross-country mountain tire has an obvious deep tooth structure, the distance between tooth lines is quite large, good grasp ability, the smooth tire grain is very small, the smooth tire resistance is small, can quickly increase speed, and can make the mountain speed to the limit.