Over-inflating tires slightly is common when using gas station air pumps, especially if the equipment or gauge is unfamiliar. Maintaining the correct tire pressure, measured in pounds per square inch (PSI), is important for vehicle performance, safety, and tire longevity. Over-inflation reduces the tire’s contact patch with the road, negatively affecting traction, braking distance, and ride comfort. Knowing how to safely release excess air is a necessary skill to ensure your tires are set to the manufacturer’s specifications.
Determining the Correct Tire Pressure
The first step before adjusting any tire pressure is to know the exact target PSI recommended for your vehicle. This number is not the maximum pressure stamped on the tire sidewall, which is a limit set by the tire manufacturer. The correct pressure is determined by the vehicle manufacturer and is found on the Tire Information Placard. This sticker is typically located on the driver’s side door jamb, though it can sometimes be found inside the glove box door or the fuel filler flap. The placard lists the recommended “cold” inflation pressure, which is the pressure measured before the tires have been driven or after the vehicle has been parked for at least three hours, ensuring the most accurate reading.
Step-by-Step Guide to Deflation
Once you have the correct PSI, begin the deflation process by parking the vehicle safely and ensuring the engine is turned off. Locate the valve stem, the small rubber or metal protrusion on the wheel, and unscrew the protective valve cap. The valve stem contains a Schrader valve, which is a spring-loaded poppet valve with a small metal pin at its center that seals the air inside the tire.
To release air, you must gently depress this central pin. The most accurate way to manage this is by using a dedicated tire pressure gauge, as many models have a small nub designed to press the pin. Alternatively, a small, pointed object like the tip of a pen or a key can be used to push the pin inward. Release air in short, controlled bursts, as air escapes quickly under pressure.
Press the pin briefly, listen for the hiss of escaping air, and then immediately use your pressure gauge to check the new PSI reading. Repeat this process of short bursts and re-checking the pressure until the gauge displays the exact PSI listed on your vehicle’s placard. This technique of releasing air in small increments is important to prevent over-deflation, which would require you to add air back using the gas station pump.
Essential Safety and Re-Check Tips
After successfully adjusting the over-inflated tire, it is important to check the pressure of all four tires, as they may have been inflated to the same incorrect pressure. Ensuring all tires match the manufacturer’s specification optimizes the vehicle’s handling and tire wear characteristics. If you accidentally release too much air and the tire pressure drops below the recommended PSI, you must use the air pump to add air back until the correct pressure is reached. Under-inflation is generally considered more detrimental than slight over-inflation, as it causes excessive flexing and heat buildup in the tire’s internal structure, which can lead to premature failure.
The final step is to securely screw the valve cap back onto the valve stem. The cap acts as a secondary seal and prevents dirt, moisture, and road debris from entering and damaging the delicate Schrader valve core, which could otherwise cause a slow leak over time. Monitoring the tire pressure over the next few days is a good practice to confirm the adjustment holds steady.