In the work of car maintenance, tires that are in close contact with the ground are always the first inspection location, and the air pressure is the life gate of the tires, too high or low will shorten the service life of the tires. When many car owners went to pump up the tires, they found that from the auto repair shop on the street to the 4S shop, they did not pump up the tire pressure according to the manufacturer’s recommended tire pressure value. All of them were driven to 2.5 bar. Car owners who know a little bit also found that the car manufacturer’s It is recommended that tire pressure, automobile tire pressure standards and national standards are different. So the question is: a national standard specifies tire pressure, a manufacturer recommends tire pressure, a tire brand specifies tire pressure, and auto repair shop default tire pressure. Which one is correct?
* Tire pressure can refer to two standards
There are two reference standards for tire pressure: international standards and factory standards. The international standards are generally easy to remember, and the factory standards are the most accurate. The international standard recommends tire pressure between 2.4bar-2.5bar, reinforced tires: 2.8-2.9bar, maximum pressure: should not be greater than 3.5bar. This standard tells us that when ordinary tires hit 2.5ABR and reinforced tires hit 2.9BAR, they each reach the highest limit of "safe load-bearing"! Due to individual tires or seasonal changes, the maximum tire pressure cannot exceed 3.5 bar, otherwise it will be dangerous. Then why is the recommended tire pressure of the factory value different?
This is because the same specifications of tires may be used in many different types of cars. Under different tire pressures, the safe weight of the tires will be different. The factory recommended value will be based on each car's body weight, chassis, etc. Factors will make the tire pressure different, the front wheel and the rear wheel are also different. The car manufacturer will accurately mark the recommended tire pressure in the vehicle manual. In addition, find the recommended tire pressure on the main driving door or fuel tank cover. Just fine.
* Why does the auto repair shop default tire pressure to 2.5bar?
The default tire pressure of 2.5bar is actually an insurance method. The number in the national standard represents the "needed pressure under the maximum load capacity", but in actual use of the car, we do not need tires to provide such extreme load conditions. For example, all models of SAIC Volkswagen will give different tire pressure recommendations according to different vehicle conditions such as "empty", "half load", and "full load", which is very complicated.I believe it is difficult for most people to achieve such rigorous inflation.
So why is it 2.5 instead of 2.4? First of all, according to the national standard GB/T 2978-2014: most cars use radial tires, the standard inflation pressure value is 250kpa (2.5bar), but in fact, the calibration tire pressure of many family cars is lower than 2.5bar . Secondly, car tires will be fully deflated due to their own reasons, and the pressure of 0.1-0.2bar will be naturally leaked for up to a month (this is in the case of healthy tires, if the tires are slowly deflated and the valves are aging, the tire pressure will drop faster ), so the tire pressure should be slightly higher when inflating. If the car owner regularly repairs the tire pressure to 2.5bar, there will be 2.3bar after one month, and 2.1bar after two months. This will ensure safety within 2 months. After all, most people do not check every month. The habit of tire pressure.
Another reason is that for the auto repair shop master, 2.5bar is easy to remember, it will not cause problems with the car, but also prevent the apprentice from making mistakes when working, so the tire pressure should be high instead of low, hit 2.5 The advantages of bar outweigh the disadvantages.
According to data, tire pressure accounts for 80% of tire problems. Too low air pressure will increase the deformation of the carcass, increase tire noise, greater wear on both sides of the tire, weakened grip, and understeer. If the air pressure is too high, the tire cord will be excessively stretched and deformed, and the carcass elasticity will decrease, which will increase the load on the car during driving. In case of impact, internal cracks and bursts will occur. At the same time, too high air pressure will accelerate the crown Abrasion reduces the rolling resistance. Therefore, an appropriate tire pressure value is an important factor to ensure tire life.
* Car tire pressure adjustment schemes under different conditions
1. Different seasons:
Winter: According to the principle of car tire standard pressure, it can be appropriately adjusted to about 0.2bar.
Summer: According to the lower limit of the standard air pressure of car tires.
In summer, the car is parked in the open air, and the air pressure can be about 0.1bar lower than the standard to avoid high-temperature tires.
2. Different tire pressure measurement environment:
Hot tire: The pressure of cold tire is different from that of hot tire. Pay attention to it when measuring. The difference between the two is about 0.3 bar.
Cold tires: after stopping at least three hours or the tires driving no more than 2 kilometers. If you can only measure the tire pressure when the tire is hot, subtract approximately 0.2 bar from the measured tire pressure to get the tire cooling inflation pressure.
3. Different tire conditions:
New tire: The tire pressure can be increased by about 0.2bar according to the standard air pressure of the car tire.
Used tires: Adjust the tire pressure appropriately according to the car tire pressure standard. If the wear is serious, press the lower limit of the car tire pressure standard.
Soft tires: tires with a comfortable pattern, which should be properly adjusted up to about 0.2bar according to the standard tire pressure.
Hard tire: that is, controllable tread tire, according to the lower limit of standard tire pressure.
Tire pressure is an empirical value. Of course, it is the most reliable according to the manufacturer’s recommendations. It can maximize the performance of the tires and let the car owner know their car better. However, if you are afraid of trouble in your daily commute and cannot be so accurate, just It is also possible to keep it between 2.0-2.5bar (the tire pressure of a general car). Please note that the four tires must be consistent.
Tisp: Low tire pressure has a higher probability of puncture than high tire pressure. If the tire pressure is 25% below the standard value, the probability of puncture will increase by 3 times; if it is 25% higher than the standard value, the probability of puncture will be doubled.
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