The right way to calculate your used tires optimal air pressure


As we have discussed in previous articles, it is very important that your vehicle’s used tires have the correct pressure for reasons of safety, efficiency and reliability and premature wear and shorter life of the used tires will occur, and be a safety hazard. We have already touched on the effects of temperature on tire pressure making it difficult to get correct readings of the pressure due to the pressures increasing with increase in tire heat caused by running even a few miles at speed. But if you reside in a region with fluctuating or extreme climate conditions, the environmental temperature alone can affect the tire pressure readings. This is why you are well advised to calculate and maintain your used tire’s optimal pressure.

In the tire maintenance section of the owner’s manual for your vehicle, look for the suggested pounds per square inch (PSI) rating. This rating is based on tests carried out by the manufacturer to measure optimal tire performance by your vehicle. Make sure the car has been sitting still overnight or in as close to ‘normal’ temperature (around 70°F) and check the used tire pressure. This is called a cold reading. Now, by checking the sidewall of your tire, find out the maximum amount of air pressure your tire can hold. Also check that all four used tires call for the identical air pressure.

Next, make a record of the conditions your vehicle will be most exposed to while driving. This means that if you happen to store your car in a temperature-controlled garage but the outside temperature when you drive it is many degrees more or less than that, then record that temperature. Then use the recommended pounds per square inch (PSI) in your owners manual to calculate optimal pressure based on the air temperature. Tire pressure decreases by around half a pound for every ten degree (Fahrenheit) drop in temperature. So add a pound for every ten degree increase in the temperature of your driving environment. After your calculations are complete, inflate your tires to the optimal tire pressures.

As always, be sure that the tire pressure gauge being used is a reliable one, made by a reputed brand and recommended by your tire maintenance professional and never inflate the used tire above its maximum capacity or it could blow while on the road.