What should my tire pressure be? Having your car’s tires inflated to the right pressures can help with fuel economy, handling and tire life. So, if you’ve noticed that your car is sitting a bit lower to the ground or that a tire looks a little flatter, it may be time to add some air. But how do you know what the proper tire pressure is for your vehicle?
What Should My Tire Pressure Be?
Because maintaining your tires is so crucial to your safety and your car’s overall performance, it’s important to know what tire pressure is correct for your vehicle. The recommended pressure for tires varies by the type of car and tire. If possible, it’s advised to check the pressure while the tires are cold because driving generates heat and increases the tire pressure.
To learn what your tire pressure should be, look for your manufacturer’s recommendation, which is printed on a label inside your car. Depending on the vehicle, this label may be on the edge of the vehicle’s door, on the doorpost, or in the glove box.
The label will usually give recommendations for the front and rear tires as well as the spare, and it’s important that you stick to those guidelines. Even after you’ve replaced your tires, the same pressure guidelines on your car’s label apply to new tires of the same size.
Pressure recommendations are based on readings taken from a tire pressure gauge. To get a proper measurement, check the pressure first thing in the morning or wait at least 3 hours after driving; this provides sufficient time for the tires to cool down.
Why Correct Tire Pressure Matters?
Keeping the correct air pressure in your tires can do wonders for your vehicle while also helping to ensure safety. Proper tire inflation can ensure even weight distribution, help your tires last longer, reduce rolling resistance, and promote fuel efficiency.
In general, tires lose or gain 1 PSI for every 10℉ change in temperature. That’s why it’s recommended that you check air pressure every other time you stop to fill up your gas tank. Keep in mind that many vehicles have different tire pressures on the front and rear axle. And don’t forget to check the pressure in your spare tire.
What Does Psi Mean On A Tire?
Tire pressure and PSI (pounds per square inch) are closely related but refer to slightly different concepts. Tire pressure generally refers to the amount of air inside the tire, which creates internal pressure that supports the weight of the vehicle.
PSI — or pounds per square inch — is a specific unit of measurement used to quantify tire pressure. In short, tire pressure refers to the actual amount of air in the tire, while PSI is the unit of measurement used to express that pressure.
The recommended PSI for tires can vary depending on the vehicle, tire size, and load requirements. It is essential to regularly check and maintain the correct PSI level to maximize tire lifespan and maintain a safe driving experience.
How To Check Tire Pressure?
You will need a tire pressure gauge and air compressor to check and adjust your tires’ PSI. These can often be found outside of gas stations and auto service centers and are typically available free of charge or for a minimal fee. Additionally, you can use a digital or analog tire pressure gauge. Digital gauges are generally easier to read.
Once you’ve located a tire pressure gauge, follow these steps:
- Check tire pressure when your tires are ‘cold’: The friction and heat caused by driving can affect tire pressure. We recommend checking your tire pressure before or at least three hours after driving.
- Remove the valve cap: Unscrew the valve cap on the tire’s valve stem. Keep the cap in a safe place.
- Attach the tire pressure gauge: Press the gauge firmly onto the valve stem to get an accurate reading. You may hear a hissing sound, which is normal.
- Read the tire pressure: Compare the gauge’s tire pressure reading to the recommended PSI for your vehicle. If the pressure is too high or too low, it will need to be adjusted.
- Adjust tire pressure if needed: If the tire pressure is too low, use an air compressor to add air until it reaches the recommended PSI. If the pressure is too high, release air by gently pressing the valve stem with the gauge until the PSI reads at the correct level.
- Repeat for all tires: Repeat the process for all four tires, including the spare if applicable.
- Reinstall the valve caps: Once you’ve checked and adjusted each tire, twist the valve caps back on securely.
- Perform TPMS reset (if applicable): Some vehicles will require you to manually reset the TPMS system by pressing and holding the TPMS button if the low pressure light was on. Most vehicles will automatically turn the TPMS light off after a short drive.
How To Check Tire Pressure Without A Gauge?
If you happen to find yourself without a tire gauge and your car doesn’t have an indicator for low tire pressure, there are several things you can do to figure out whether your tires need to be inflated.
- Feel the tires. Press on your tires using your hand or foot. Are the tires firm or do they have some give? If they feel soft, you may need to add more air.
- Do you see any flattening in the tires? If yes, then your tires probably need more air.
- Load weight onto your vehicle. If you see your tires sagging a bit with more weight added to your car, then you probably need to inflate them more.
- Pay attention to how your ride feels. Do you notice any noise from the tires when turning? Do you have difficulty steering? Does the ride feel rougher? These are signs that your tires might be low on air.
Finding Your Car’s Recommended Tire Pressures
Nearly every vehicle lists the manufacturer-recommended tire pressures on a sticker affixed to the driver-side door jamb, which is the body pillar the door locks into. It could also be on the rear edge of the door itself, in the glove box or on the inside of the fuel-filler door. You can also find it in the owner’s manual.
Although this may seem like a clear, simple answer, there are a few things to keep in mind:
- The recommended tire pressure is a cold inflation pressure, which means the pressure check should be done after the vehicle has been sitting in the shade for a while. This can be trickier than you might think. Things that can throw off the reading include the car being in a garage that’s warmer (or colder) than the outside temperature, having the sun hitting one or two of the tires, or having driven on them for more than a couple of miles. (See the section on how temperature affects tire pressures below.)
- Some vehicles have different recommended inflation pressures for the front and rear tires, and sometimes a higher pressure (usually for the rear) will be listed for if you’re carrying a heavy load.
- If your car has a spare tire (some newer ones just have a sealing kit and a pump), don’t forget to check the pressure in that, as well, as air can leak out over time. (Note that some are small “doughnut” temporary spares that run much higher pressures than the regular tires.) Unfortunately, this isn’t always easy. Spare tires mounted under the rear of the vehicle are particularly troublesome in this regard, as they may need to be removed to check the pressure.
- The pressures listed are for the tire size that originally came on the vehicle, which is also listed on the sticker. If different-sized wheels and tires have been installed, the listed pressures won’t necessarily be optimal.
While the sidewall of the tire usually lists a pressure, that’s a maximum safe inflation pressure, not what’s recommended for its use on a particular vehicle.
How Temperature Affects Tire Pressure
A general rule of thumb often quoted is that tire pressure fluctuates by 1 pound per square inch for every change in temperature of 10 degrees, as air in the tire expands when it gets hotter (raising the pressure) and contracts when it gets colder (lowering the pressure). Though the rule is easy to remember, it isn’t really accurate for all tires and can be closer to 2% per 10 degrees.
This mostly affects you when the temperature drops in the late fall or winter if the tires were last checked and inflated in the heat of summer. In that case, a tire could easily lose 7-10 psi between June and January, and that could mean trouble. Low tire pressures can result in poor handling characteristics, particularly in emergency maneuvers; increased risk of a blowout; and premature tire wear.
Drivers of modern cars often get this called to their attention when the tire pressure monitoring system warning light, which typically looks like a “U” with an exclamation point in the center, illuminates on the instrument panel.
The light usually comes on when the tires are determined to be 25% below their recommended pressures. This can also work in reverse: Tires properly inflated in the winter can be running too high a pressure as the weather warms; thus, some air should be let out to drop them to proper pressure — though running a slightly higher pressure than recommended isn’t as bad as running too low a pressure.
Driving the car will heat up the tires due to friction with the road, and it takes some time for them to cool down. Sun shining on the tires can also heat them up. In either case, the added heat increases the air pressure inside the tire, which is why it’s best to check pressures early in the morning after the car has been sitting overnight.
How Does Tire Pressure Affect Driving
Both overinflation and underinflation affect your tire performance a lot, and serious problems might occur. According to NHTSA(National Highway Traffic Safety Administration), driving on underinflated tires increases a driver’s chance of being in a serious accident by 300%. So how will a bad tire pressure affect driving safety? We will explain in detail below.
How tire pressure affects grip
The grip is mostly associated with the size of the contact patch between the tire and the road. An over-inflated tire radically decreases the contact patch while an under-inflated tire does the opposite.
A larger contact patch gives you more grip, and this is the exact reason why lots of racers will intentionally decrease their tire pressures to create a larger contact patch on a dry race track.
However, despite the fact that an under-inflated tire will cause more fuel consumption and improper tear and wear of the tires, for most daily commuters, it might cause an even scarier problem, which is hydroplaning.
Hydroplaning is a hazardous event when a layer of water builds between the wheels and the road surface, leading to a loss of traction that prevents the vehicle from responding to control inputs. (Appx2)
Hydroplaning occurs when the pressure of the tire pushing on the ground is equal to the water pushing back up on that tire. The size of the contact patch, given the force or the weight of the tire, is the same, directly affects the average pressure the tire’s putting down on the road.
The larger the contact patch (by deflating the tires), the less pressure it puts on that same area. So there’s a causal relationship between your tire pressure and the possibility of a hydroplaning event.
Here’s a more visual explanation of what is happening between a properly-inflated tire and an underinflated tire when driving on a wet road.
To avoid a hydroplaning event, ALWAYS inflate your tires properly. Also, check your tires’ treads, which make the water flow around the tires more efficiently, and of course, driving slow is always a big plus.
How tire pressure affects tire wear
The contact patch directly decides the pattern of the tire’s wear and tear. You don’t want your tires to wear out prematurely just because you have an over or under-inflated tire.
How tire pressure affects fuel economy
Imagine you are a ball rolling on the ice, there’s no friction between the two surfaces, how much extra force do you need to apply to keep the ball moving? Zero (Thanks, Newton). The same applies to your fuel consumption when it comes to driving on the road.
The rolling resistance between your tires and the road significantly affects fuel economy, and by now we should all know the logic behind this, lower tire pressure leads to a larger contact patch, which causes higher rolling resistance, and thus, poor fuel economy.
A Michelin study showed that your tire is accountable for at least 1/5 of your total fuel consumption and a 1-bar of pressure drop (14.5 psi) would increase your fuel consumption by 3-5%.
How Often Should I Check My Tire Pressures?
The common rule is to check your tire pressures once a month, but who wants to do that? Unfortunately, even that may not be enough. It’s ultimately your call on how frequently you check them, but a visual check (comparing the ground contact patch on the front tire to the rear on the same side to see if one looks low) is worth doing every time you approach the car.
However, with modern low-profile tires, differences aren’t as noticeable as they used to be.
Aside from the aforementioned pressure changes due to temperature swings, tires often lose a little bit of air just from normal leakage. Worse is that they can also lose some due to a slow leak from a nail or screw in the tire, or if they suffer a harsh road impact such as from hitting a pothole. Thus, even if you live in a very temperate climate, the pressure can drop over time, which may well be less than a month.
As for an actual tire pressure check, a minimum would be a warm day in late spring and a cold day in late fall due to the change in temperature, keeping in mind what temperatures lie ahead.
For instance, if it’s a 32-degree day in late fall and you know zero-degree temperatures are likely coming, you may want to add a few extra psi to compensate. It’s not really a problem if your pressures are a little higher than recommended, as you’ll mostly just have a slightly stiffer ride.
How To Maintain Proper Tire Pressure
Of course, knowing your recommended psi isn’t enough. You must ensure that you’re checking your tires regularly. It’s recommended that you check air pressure once a month. Your car’s tire pressure monitoring system (TPMS) measures the amount of air in your tires to let you know whether your tires are properly inflated.
Frequently checking your psi becomes even more important in the fall and winter, when outside temperatures drop and weather conditions fluctuate, causing your tires to lose pressure more quickly.
Generally, your tire will gain or lose psi for every 10-degree change in temperature, which means if you have a sudden drop of 30 degrees, you could lose 3 psi overnight. If your tires were already low, this could cause tire damage, steering problems or even a flat tire.
How do I know the correct tire pressure?
Your vehicle’s recommended tire pressure can typically be found on a sticker inside the driver’s door. It’s also usually listed in the owner’s manual, says Cars.com. Tire pressure is measured in pounds per square inch (psi). You may also notice that the sidewall of the tires lists a tire pressure.
What causes low tire pressure?
Low pressure could result from a leak or simply from the tendency of a tire to lose about a pound of air pressure every month, as well as a pound for every 10-degree drop in temperature.
Is higher tire pressure OK?
There are a variety of issues that can occur if you drive on overinflated tires. Most seriously, overinflated tires are at greater risk for a blowout. A tire blowout can cause you to lose control of your vehicle and negatively affect braking distance, endangering yourself and others on the road.
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