In the summer, how to run flat tires has become the most concerned thing for many car owners. According to statistics, about one-third of traffic accidents on expressways are caused by tire failures, and the most important one is a puncture. Ever since, knowledge about car summer run-flat tires emerges endlessly. It is said that lowering the tire pressure can cause a run-flat tire, and it is also said that a nitrogen-filled tire can be run-flat. So, are these methods of run-flat tires on the Internet reliable?
Speaking of summer run-flat tires, the first idea that many people have in their heads is usually to lower the tire pressure. Because everyone has learned the principle of thermal expansion and contraction. Gas expands when heated. If the air pressure inside the tire is too high, it will easily burst when heated. Therefore, many car owners will naturally lower the tire pressure by 0.1-0.2BAR after entering the summer. However, this seemingly reasonable approach will actually backfire.
Because there are many steel wires inside the tire to hold the entire tire. When driving under the condition of insufficient tire pressure, due to the irregular deformation of the tire, the steel wire inside the tire continuously deforms. As a result of the continuous deformation of the steel wire, the temperature of the steel wire rises sharply and it is easy to break. Coupled with the increase in tire temperature during driving, the possibility of a tire blowout will increase. Increasing the tire pressure by 0.1 or 0.2 BAR from the normal value can effectively reduce the deformation and fracture of the steel wire inside the tire caused by the deformation of the tire, thereby reducing the possibility of tire blowout. Therefore, reducing tire pressure is not reliable!
Nitrogen filling is also considered a “good” method for run-flat tires in summer. Because nitrogen is an inert gas, the free path of molecules is larger than that of oxygen, and the permeability in rubber is low. Therefore, the tire pressure drop rate is greatly reduced, and the time to maintain the normal tire pressure increases. At the same time, the volumetric expansion of nitrogen gas is much lower than that of air containing moisture when the temperature changes, thus reducing the chance of puncture.
However, someone once did an experiment in which nitrogen and air were respectively filled on the left and right tires of the same car. Then, record the tire pressure and temperature every 10km, and the final result is that the characteristics of “nitrogen’s low thermal expansion coefficient, low thermal conductivity, and slow temperature rise” are not effective in practical applications. Therefore, it is not advisable to inflate the tires with nitrogen to prevent punctures in summer.