Over-inflated tires have long braking distance and are easy to slip on rainy days, also the middle part of the tire will wear too fast. Under-inflated tires need to consume more fuel while driving, not good for purses and the environment. A resonable inflated tire save fuel, increase the tire's lifespan, improve the driving experience, and insure the driving safety. Please use tire pressure gauge to test the wheel pressure every week regularly when the tire is cold, especialy before long distance travel.