Section width Ratio Radial Rim Diameter Loading Indexr Speed Level
Section width (mm) :
the distance between both sides when inflated.
Also called aspect ratio, section height / section weight. The section weight is half as the difference between outside diameter and rim diameter.The lower the ratio is, the wider the section width will be, which means it will be safer to drive. The elasticity of sidewall will increase corresponding to the section width to make driving more stable. The high-speed cars using low ration tires is a trend nowadays.
The speed level is marked on sidewall of every tire, which will indicate the maximum speed. For example: for the size 255/45R20 105W, the speed level is W, so that the max speed will be 270Kilometer/hour by referring the speed comparison table. The speed level and specific info will be marked on all the stickers for every brand。
The tire has bigger chance to get damage when driving at high speed, and the reaction time to avoid the accident will be reduced as well. For your own safety, you are suggested not to exceed the max speed according to the legislation at every driving condition.
The loading index is marked on sidewall of every tire, and the max loading capacity is marked as well. For example: for the size 255/45R20 105W, the loading index is 105, which corresponds the max loading capacity is 925 kilograms. Overloading will make tire over heated and break abruptly.