Why is there a discrepancy between the tire pressure monitoring system and the air pump display?
3 Answers
Strictly speaking, any instrument will have some degree of error. Between the air pump pressure gauge and the tire pressure monitoring system, the tire pressure monitor is more accurate. Here's relevant information: 1. Tire pressure range: Cold tire pressure of 2.3, 2.4, or 2.5 bar is normal, and after driving some distance, 2.5 or 2.6 bar is considered normal - it should not exceed 2.8 bar when the pressure is high. 2. Considerations: When tire pressure is high, the contact area between the tire and the road is smaller, resulting in poorer grip, longer braking distances, more noticeable bumps, and reduced comfort, but with lower rolling resistance and relatively better fuel efficiency. When tire pressure is slightly lower, the contact area with the road increases, improving grip and comfort, but with higher rolling resistance and increased fuel consumption.
I found that the readings from the tire pressure monitoring system and the air pump often don't match, mostly because the air pump itself has poor accuracy. Ordinary portable air pumps may not be precise, with errors reaching 2-3 psi, while the vehicle's built-in tire pressure monitoring system is calibrated and more reliable. I recommend first checking the accuracy of the air pump using a professional pressure gauge or confirming it at a service station to avoid misleading operations. Also, weather factors are important—tire pressure increases when driving in high temperatures, and measuring after the vehicle has cooled down will show lower readings, while the TPMS can display real-time values. It's best to compare readings in the morning when the vehicle is cold, as the difference will be smaller. Regular maintenance of the air pump to avoid long-term dust buildup affecting readings can also reduce this issue. If inconsistencies persist, don't overlook TPMS battery issues—sometimes, low sensor battery levels can display unreliable data, affecting driving safety.
I think this is a common issue, mainly caused by changes in ambient temperature. When the car is cold, the tire pressure is low, and after driving when the car heats up, the tire pressure rises. The TPMS captures dynamic values, while the air pump measures static values, so naturally, there's a difference. From my experience: in summer, after driving and parking on the roadside, the air pump shows normal pressure, but the TPMS alarm indicates it's high—this is due to hot tire expansion. For an accurate assessment, wait for the car to cool down for an hour before checking, and the two readings will be closer. Also, don't forget the impact of air temperature and atmospheric pressure—differences are smaller on dry sunny days, while errors are larger in high humidity. If the air pump is an old model or of poor quality, the readings can fluctuate significantly; switching to a digital tool is more accurate. Incorrect tire pressure greatly affects tire wear: low pressure saves fuel but increases the risk of a blowout, while high pressure reduces comfort. It's recommended to calibrate monthly according to the recommended values in the vehicle manual.
