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Taking care of your tires will not only save you money, but may also save your life and the lives of others. Maintaining the correct tire pressure is one of the most important car maintenance considerations, and it’s arguably the easiest to perform – but it’s the task that’s most often overlooked.
Tire pressure can affect a car’s gas mileage, acceleration, steering, braking, ride, and handling. However, unlike a smoking engine, terrible smell, loud noise, or car that won’t start, tire pressure isn’t always as obvious to drivers. Fortunately, many newer cars have tire-pressure monitoring systems, but you can’t completely rely on them (more on that later).
In order to properly inflate your tires, you need to know what the pressure should be, and have the proper tool. Finally, you’ll need a way to refill them.
Where to Find Your Car’s Recommended Tire Pressure
There are many places to find your car’s recommended tire pressure, which is measured in pounds per square inch (psi).
- Driver’s door jamb: Most often, it’s printed on a sticker inside the driver’s door jamb.
- Glovebox or trunk: You may also find it posted in the car’s glovebox or on the inside of the trunk.
- Owner’s manual: In addition, it’s always listed in the owner’s manual.
If you can’t find the sticker or don’t have an owner’s manual, you can call a dealership or find the information online. However, be sure to consult a few sources to make sure the number is accurate.
Typically, manufacturer-recommended psi is between 30 and 35, though there are exceptions.
One place it’s not: On the tire itself. Tires will show the maximum amount of pressure allowed, but that’s virtually never the amount you want to fill it to.
How Do Car Companies Determine Recommended Tire Pressure?
Tire manufacturers rely on a set of standards and guidelines to determine maximum pressure and load for each size of tire. However, those tires will end up on vehicles of different styles, weights, and sizes. For this reason, automakers use a series of tests to come up with the ideal tire pressure for each car or truck. Ideal pressure provides the best possible balance of performance, fuel economy, safety, and tire life.
Why Filling Your Tires to the Recommended PSI Is Important
To get the best performance, gas mileage, and tire life, keeping the tires at their recommended psi is paramount. It greatly reduces the chances of tire failure.
Some common car issues can make it difficult to drive your car without getting it fixed, but it’s easy to drive a car with improperly inflated tires. In fact, a tire can be very low on air and still look normal. However, in the event of an emergency maneuver to avoid an accident, an improperly inflated tire won’t respond as well as one that’s got the proper amount of air. Even worse, a blowout can leave you stranded or cause an accident.
What Tire Pressure Is Too High?
Tires can usually be inflated to a pressure that’s much higher than the automaker recommends. If you look at a tire’s sidewall, you’ll see a maximum inflation pressure number that can be nearly double the vehicle’s recommended number. However, overinflating your tires is not a good idea.
Some people suggest that adding extra pressure is good: They claim it’ll improve fuel economy, allow the car to carry extra weight, or even improve some performance metrics. While this could be true in some cases, it’s not consistent. The extra air pressure reduces the tire’s contact with the road, which not only reduces friction, but also decreases traction. Your car could become more difficult to control, the ride will be rougher, the stopping distance will increase, and there’s a greater likelihood of having a blowout.
What Tire Pressure Is Too Low?
Low tire pressure tends to be more dangerous than high tire pressure. Generally, tire pressure monitoring systems alert you when your tire pressure drops by 10 percent and/or when a tire’s pressure is 25 percent below the automaker’s recommended psi.
If you notice that your tire pressure is down a few pounds, and it’s a short trip home on local roads, you can probably wait until you get home to assess the issue.
However, if you have a tire that’s underinflated by several pounds and/or losing pressure rapidly, it’s best to stop. This is especially true if you’re driving at high speeds and have a reasonable distance left to travel.
When tire pressure is too low, the tire has greater contact with the road, and the tire’s sidewalls flex more. This causes extra friction, which leads to increased wear and tear, as well as reduced fuel economy.
If a tire is more severely underinflated, it can make the vehicle much more difficult to control. It can also take a toll on the car’s suspension, steering, and braking systems.
Why Did My Tire Pressure Light Go On?
Many newer cars come standard with built-in tire pressure monitors. They’re linked to a dashboard light that alerts you if your tire pressure is incorrect – it’s usually yellow or orange and looks like a cross-section of a tire with an exclamation point or the letters “TPMS,” which stands for Tire Pressure Monitoring System. Sometimes the car will have a tire pressure menu that allows you to view a readout of each tire’s current psi.
If your tire pressure light comes on, take it seriously. Sometimes it flickers or turns on briefly and then turns off; other times it flashes repeatedly or stays on. No matter what the light does, you should check your tire pressure immediately (as soon as it’s safe).
The flickering or brief illumination could be as simple as a change in pressure due to temperature or an imperfection in the road. Flashing sometimes indicates that the sensor or the sensor’s battery needs replacing. If the light stays on solid for a time, there’s a good chance you have a tire pressure issue. If you check the pressure and it’s fine, you may have a failing sensor, and you should get it replaced as soon as is practical.
Why Do My Tires Have Green or Blue Caps?
In the mid-2000s, filling tires with nitrogen got very popular.
Nitrogen is a popular and inexpensive alternative to air with some additional benefits. Nitrogen is dryer than air, reducing the impact water has on inflation. Nitrogen is also bigger at a molecular level. This reduces the amount of gas lost to microscopic leaks.
The bottom line is that nitrogen is more stable than the air we breathe, and many people feel it is a better choice for filling tires.
When a shop fills tires with nitrogen they will typically replace the valve caps with ones that are green or blue. This is to let the next person filling your tires know what is in them.
Mixing air and nitrogen is perfectly safe, but doing so dilutes the nitrogen and offsets the benefits.
How Do I Check My Tire Pressure?
For about $5 to $15, you can get a simple, manual tire pressure gauge. You can find them at your local auto parts store or retail outlets such as Target or Walmart. You can also find countless options on Amazon.com.
Follow these steps to check your tire pressure:
- Take off the valve cover cap.
- Press the gauge onto the nozzle.
- Listen for a burst of air.
- Placement and pressure of the gauge on the nozzle are critical to getting an accurate reading.
- We suggest doing it a few times to make sure you’re getting a consistent reading.
Types of Tire Gauges
A manual tire pressure gauge is easy to use and cheap, though they can sometimes be hard to read.
For a more reliable reading, you can use a digital tire pressure gauge. Some cost as little as $10, but you can spend up to $50 on a fancy one. They’re less finicky and easier to read, but they do require batteries that will eventually need replacing.
Check Your Tire Pressure Before You Drive, Not After
Regardless of which type of gauge you use, it’s important to check your tire pressure when the tires are cold. Once you start driving, your tires heat up and the pressure rises. Checking pressure after the car has been sitting for several hours will ensure the most consistent reading. Moreover, the manufacturer’s suggested tire pressure assumes you’re testing the tires when they’re cold.
Check Your Tire Pressure at Least Once a Month
It’s wise to check your tire pressure at least once a month, and every time the temperature changes by about 10°F.
That’s because the rubber of the tire and the metal rim can expand and contract at different speeds, especially when the temperature changes in wide swings. That can let air escape from the tire, even if it’s not being used much.
In addition, even when the change in temperature doesn’t impact the amount of air in the tires, it will still affect the tire’s air pressure.
Options for Filling Your Tires
If you need to add air, you can use a hand pump, though a compressor is a better option. If you don’t have a compressor, you should be able to find a local gas station or car wash that has one available for use. Be prepared and bring quarters; many stations charge to refill tires. The site freeairpump.com has a handy map of places with free air for your tires.