Pumping up to the PSI number on your tire is a terrible idea: here’s why – Jalopnik

So you notice that one of your tires is low on air and you pull into a gas station to use the air machine. Or maybe you have one of those handy portable tire inflators. But wait! The air machine asks for the PSI number: which is pounds per square inch. How do you know how much air to put in the tire? Simple! Just look at the side of the tire, right? After all, the number is right there, right next to ‘PSI’, right? Wrong! That’s not the number you should pay attention to!

Inflating your tire to the PSI number printed on the side of it can cause the tire to be over-inflated, putting you in danger. But why would the tire manufacturer do that to us? Before you start feeling betrayed by the Michelin Man, you might want to take a closer look at what’s actually on the side of the tire. It usually says ‘max PSI’ or ‘maximum PSI’. In other words, that is the upper limit of air pressure that the tire is built to withstand. It is certainly not the pressure your tires should always have.

The recommended tire pressure is set by your car’s manufacturer and is usually well below the maximum PSI number printed on the side of your tire. You can usually find it somewhere in the car, usually on a sticker on the driver’s side door jamb. It’s important to stick to this number because driving on over-inflated tires can cause a lot of problems and, if you’re like us, you’ve had enough of that.

Too high tire pressure causes the tread of your tires to wear unevenly. This is because the increased air pressure pushes the center portion of the tread outward, rather than creating a punctured tire surface that makes contact with the road. This can significantly shorten the life of your tires. By the way, here are some ways to extend the life of your tires. Also expect a less comfortable ride. Overinflated tires are stiff and inflexible, meaning they don’t provide much cushioning in contact with the road.

But over-inflated tires can also make it harder to control your car, especially on wet roads. That’s because less of the tire grips the road, resulting in less traction. And because there is less traction, it can take longer for the car to come to a complete stop on any surface. Excessive inflation also increases your chances of a blowout, for a few reasons. One reason is that the stiffness and inflexibility make the tire more vulnerable to bumps, foreign objects and potholes. Over-inflated tires can also puncture more easily (think of how much easier it is to pop a very full balloon rather than a partially inflated one). And excessive pressure is placed on the sidewalls, making it more difficult for them to withstand the force of the impact.

But what if you haven’t had a nice new car built with one of those newfangled TPMS things in the last ten years? How should you determine the correct PSI? The most common reference people use to find the recommended air pressure is usually found right on the door jamb of your driver’s side door. There is a sticker with a number of numbers, including the recommended PSI. If the sticker is missing, damaged, or has been painted over, you can look for a similar sticker elsewhere on your car, or look in the owner’s manual. If all else fails, you can always check with Google.

There may be situations, such as when towing, where you may want to temporarily inflate the tire slightly beyond the recommended PSI, but not go beyond the maximum PSI. Sometimes – for example when driving on soft roads – you may want to underinflate your tires. But in most scenarios, make sure your tires are inflated to the recommended PSI, and never to the maximum PSI.