Why is the car tire always underinflated?

[RoseLynn]

Car tires frequently being underinflated is usually caused by air leaks in the tires or valve stems, which requires inspection at a tire shop. Deformation of the wheel hub can also reduce the tire's sealing performance. Long-term overloading of the vehicle causes uneven tire stress and thermal expansion/contraction. Due to manufacturing variations in tires, thermal expansion/contraction may lead to insufficient tire pressure. Below are relevant details: Low car tire pressure increases fuel consumption: Maintaining proper tire pressure can reduce fuel consumption by 3.3%. If tire pressure drops by 30%, when driving at 40km/h, fuel consumption increases by 5%~10%. Just one tire being underinflated by 40PSI will reduce that tire's lifespan by 10,000 kilometers and increase the vehicle's total fuel consumption by 3%. Low car tire pressure accelerates tire wear: When a car's tire pressure is insufficient, it means the tire will experience more wear, which is detrimental to the tire's service life. From the perspective of tire wear, if the pressure is too high, the center part wears more heavily; conversely, if too low, the edges wear more. Either too high or too low will affect the tire's lifespan.

[NolanFitz]

It's quite annoying when the tire pressure is always insufficient. I've encountered this issue a few times in my driving experience. The main reason is that there might be small holes or damages on the tire, such as being punctured by nails or scratched by small stones, leading to slow air leakage. This is especially common when frequently driving on rough roads. Another common issue is the aging or loosening of the valve stem (the valve), which can cause slow air leakage. I once solved the problem by replacing the tire valve when I got new tires. The tire material itself, like aging rubber, can also lead to poor sealing, particularly for tires that haven't been replaced for several years. I recommend buying a simple tire pressure gauge and checking the pressure every time you wash the car or refuel. Maintaining the correct pressure ensures safety, improves fuel efficiency, and extends tire life, rather than waiting until you feel the car drifting or unstable while driving.

[DiHannah]

Insufficient tire pressure can lead to major issues. I pay close attention to safety in my daily driving because it involves the risk of tire blowouts, especially on highways. Possible causes include small cracks on the tire sidewalls, which can worsen air leakage under high-speed pressure, or poor sealing due to rust and corrosion at the rim-tire contact point, leading to air seepage. Temperature changes have a significant impact—cold winter air contracts, causing pressure to drop faster, so monthly checks are necessary. Don’t rely too much on the vehicle’s alarm system, as it can sometimes be insensitive. I usually have a professional mechanic use ultrasonic equipment to detect leaks, ensuring a thorough fix and avoiding frequent refills. Additionally, I adjust my parking habits to avoid sharp objects on the roadside, preventing accidental damage and ensuring safe family travels.

[StColeman]

The most likely reason for frequent low tire pressure is still air leakage. When I first started driving, I was also confused—for example, not realizing the tire was punctured by small foreign objects or the valve wasn't tightened properly, causing air to slowly escape. Every time the tire pressure is low while driving, you'll feel the steering is unstable and fuel consumption increases. Checking it yourself is simple: apply soapy water to the tire surface; if bubbles appear, that's the leak point. Immediately go to a repair shop to patch the tire or replace the part, and it'll be fixed—don't delay too long. Develop a daily habit of using a manual pump to regularly check and maintain normal pressure. This saves money and gives peace of mind, avoiding the hassle of repeated repairs.