Last Updated December 9, 2022
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The maximum safe pressure for your tires is displayed on the sidewall of the tire. However, the recommended tire pressure is vehicle-specific and can be found in two main areas. Firstly, the recommended tire pressure will always be located in the user manual. Secondly, most vehicles have the recommended tire pressure listed on the door jamb sticker.
You should not fill your tires to maximum tire pressure, which is displayed on the sidewall of the tire. Among other things, this can lead to structural failure of the tire. Such a failure will most likely result in a blowout. Unless you are off-roading, you should try to keep your tires at your vehicle’s recommended tire pressures.
What's In This Guide?
Filling your tires to maximum pressure is a dangerous game to play. The main reason is the risk of a blowout. Even coming close to the thresh hold of maximum tire pressure is dangerous. As the tires heat up while being used, the pressure inside the tire increases. This is caused by a process is called thermal expansion.
As the tire experiences thermal expansion, the pressures inside the tire can build up way past the maximum PSI. Eventually, this will pop the tire just like an overinflated balloon, which we call, a blowout. The blowout is the most dangerous problem caused by over-inflation of the tire, however; there are a few other issues that can not only cause great discomfort but can also lead to accidents.
Some of us tend to forget that the tire is a part of the vehicle’s suspension system. The air inside the tire acts as a cushion that absorbs impacts from an uneven road surface. Many people that use extremely low-profile tires suffer from bent rims. When a low-profile tire hits a pothole there isn’t enough cushion to protect the rim.
This can be offset by the tire if its sidewall is extremely rigid, but the occupants of the vehicles will feel every little bump. This can also be your experience if you over-inflate your tire. If the PSI is too high in the tire it cannot give way to cushion the blow from a bump or pothole.
Furthermore, because of the high air pressure in the tire, the side wall is held rigid, preventing it from flexing. This in itself can cause a blowout. Because the tire cannot flex or bend, the force and mass of the vehicle bearing down on the edge of a pothole, or a bump causes the rubber of the tire to crack or tear.
Your tire is the only thing keeping you on the road and going in the direction you want to. It does this with surface tension The more of the tire that is touching the road surface, the better your traction will be. Unfortunately, an overinflated tire bulges out on the centerline.
With overinflated tires, you only have a thin centerline of rubber keeping you attached to the road. This translates to worse handling and less stopping power. It also means that over time the tires will have increased wear down the center, which will dramatically reduce the life span of your tires.
Why are you more likely to receive a puncture with higher levels of PSI in your tires?For the same reason, you are going to feel every bump and dip, you are more likely to get a puncture. Due to the higher pressure, the tire is unable to give way. This makes it easy for a puncture to occur.
You can demonstrate this by trying to pop and semi-inflated balloon and a fully inflated balloon. The fully inflated balloon will pop long before the semi-inflated balloon does.
The safe bet with tire pressure is to stick to the recommended PSI values found on the door jamb sticker. However, there can be some exceptions to this rule. When the manufacturer sets these values, they have a certain tire in mind. Let’s say the tire the manufacturer is working with has a maximum PSI of 35 and they recommend that you use 32 PSI for the fronts and 28 PSI for the rears.
By the time you need new tires, you buy the ones you like, and it turns out their maximum PSI is 44. No big deal, right? You are still well within the maximum limit. Wrong, 32 PSI on a tire with a max of 35PSI will not handle the same on a tire with a max of 44 PSI. The correct pressures for a tire with a max of 44PSI will most likely be 41PSI on the fronts and 36 PSI on the rears.
Additionally, pickup trucks will often have much higher PSI recommendations for the rear than the fronts. This is done so they can support weight in the back or support the weight of a trailer. However, when there is no load, the back can bounce around quite a bit, especially on dirt or gravel roads. For this reason, it is not a bad idea to decrease the PSI from say 72 PSI to 50 PSI. Just make sure you readjust the pressures before adding a load again.
As long as you stay within the recommended range the manufacture provides, you should be good. However, if you need to increase the PSI because you are towing or moving something heavy, or you simply don’t have the recommended specification, you can use the maximum PSI as a rough guide.
A good rule of thumb to use is 75% of the total maximum pressure displayed on the tire. For a tire of 50PSI, the more pressure you want to safely use is 37.5PSI. This number is easy to get, just take the maximum PSI (50) and times it by .
75. You could go as high as 90% of the maximum but at the end of the day, you will want to stay as close to the recommended manufacture’s values as possible.
Filling your tires to the maximum tire pressure is a bad idea. Not only will it give you a myriad of issues such as an uncomfortable ride and bad tire degradation, but it can also be extremely dangerous. The main thing you want to do is match your vehicle manufacturer’s PSI recommendations as closely as possible. The best time to check and adjust your tire’s PSI is early in the morning while they are still cold.
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When it comes to driving safety, tire pressure is always one of the hottest topics. Why does tire pressure matter? What the heck is that little annoying symbol on my dashboard? Should I under-inflate my tire during the winter? How often should I check my tire pressure?
We got tons of questions like this from our community, so for today, let's dive deep into the world of tire pressure, put our geeky glasses on and figure out everything you need to know about your tires.
1. What's The Recommended Tire Pressure For My Car?
The recommended tire pressure varies based on the vehicle makes determined by the manufacturer after thousands of tests and calculations. For most vehicles, you can find the ideal tire pressure on the sticker/card inside the driver’s door for newer cars. If there’s no sticker, you can usually find the info in the owner’s manual. Normal tire pressure is usually between 32~40 psi(pounds per square inch) when they are cold. So make sure you check your tire pressure after a long stay and usually, you can do it in the early morning.
2. How To Check The Tire Pressure?
After knowing the proper tire pressure of your vehicle recommended by the manufacturer, you should check your tire pressure regularly to make sure that you are in good shape.
You can check your tire pressure in auto part stores, the mechanics, gas stations, and at home. To check tire pressure at home, you need:
As tire pressure changes with the temperature a lot, and recommended tire pressures are cold inflation pressure, you should start with cold tires if possible.
We mostly check the tire pressure after one night's rest to avoid the heat from the friction of the last drive, and before the temperature goes up.
Unscrew the valve cap and press the tire gauge onto the valve stem hard enough until the hissing sound disappears. There should be a reading as long as the gauge is well connected to the tire.
You can then note down the tire pressure of each tire, and compare them with the ideal psi you read from inside your driver’s door or in the owner’s manual. Make sure you read in detail, as for some vehicles, front and rear tires have different recommended psi.
If you find a tire underinflated, use the air compressor to fill your tires. You can either buy an air compressor in the auto parts store or use one in a gas station. Remember to rest your tires for at least half an hour to make sure they’re cold and the reading is accurate.
If you have to fill your tires when the tires are hot, inflate them 3~4 psi above the recommended psi, and check again with your gauge when they are cold. It’s ok to overinflate a bit when filling the tires, as you can let the air out with the gauge.
After filling the tires, use your tire pressure gauge to check the tire pressure again and make sure they are in a good range. Let the air out a bit if they are over-inflated by pressing the gauge harder on the valve stem.
3. How To Maintain Proper Tire Inflation?
Tire maintenance is essential for the overall performance of your vehicle, and we highly recommend that you check your tire pressure every time you inflate your tire, each 10°F (5.6 °C) temperature change, and every 30 days.
Be mindful that don’t wait until the TPMS(Tire Pressure Monitoring System) light come on before you check the tire pressure, as the normal TPMS may:
..For more information about the tire pressure monitoring system, please check our post about TPMS: What is TPMS and Why Does it Matter?
Thus, we highly recommend that you check your tire pressure regularly, especially before a long drive or heavy load driving. Also, temperature affects the tire pressure a lot, and we will explain it in the next section.
4. How Does Temperature Affect Tire Pressure?
First of all, the rule of thumb is for each 10°F (5.6 °C) decrease in temperature, the tire pressure will drop by one psi for most passenger vehicles. When it comes to commercial truck tires, which are often inflated to over 80 psi (twice as much as a passenger vehicle tires), the change of tire pressure according to temperature is doubled to 2 psi for every 10°F.
For the non-nerdy readers, just remember this rule of thumb and keep in mind that you will need to monitor your tire pressure during different seasons or a sudden temperature change.
For those who want a deeper dive into how psi's are determined, here's the science behind it.
The equation we use to calculate the relationship between tire pressure and the temperature is called the Ideal Gas Law. It is a good approximation of the behavior of many gases under many conditions. (Appx1) It works well for most low-pressure gases. When applied to tire pressure calculation, the error is less than 1%.
First, we take the Ideal Gas Law equation and apply it to our circumstance:
where,
P = absolute pressure
V = gas volume in the tire
n = the number of molecules of gas in the tire
R = universal gas constant
T = temperature
Since we are trying to examine the pressure change according to the temperature, let's assume two tire pressures P1 & P2 at their set temperatures T1 & T2.
Given the n and R are both constants, and the gas volume in the tire is also a constant, we can take those constants out of the equation, and suddenly we get this straightforward one:
Let's say the temperature drops from 100°F to 50°F, the tire pressure at 100°F is 35 psi, so what's the tire pressure now at 50°F?
(the metric system is getting in the way, huh?)
Absolute Pressure = tire pressure + sea level air pressure (14.7 psi). So,
Put all that into the equation,
So a 50°F drop in temperature lowers the air pressure by 4.5 psi, which is pretty much the same according to our rule of thumb.
5. 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.
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 wearThe 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.
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%.
6. Special Conditions For Tire Pressure Manipulation
There are of course circumstances where you want to manipulate your tire pressure to meet specific requirements.
Like the aforementioned track race, or if you are driving on sand, mud, etc. However, as a daily commuter, we strongly suggest you regularly check your tire pressure, preferably once a week and anytime you might take a long road trip, and always keep the tires properly inflated!
Conclusion
Tire pressure is always a hot topic regarding driving safety, and it's important to keep an eye on the tire pressure to maximize fuel efficiency and safety.
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Appendix 1 - Ideal gas law - Wikipedia.
Appendix 2 - Aquaplaning - Wikipedia.
Consumer disputes over the age of tires have not subsided for several seasons. Buyers are excited that the warranty period for tires is limited to 5-6 years according to GOST, and after the expiration of this period, the rubber becomes unusable.
Is this really the case, read this article.
Manufacturers of most brands on their products set Shelf life is 5 years and service life is also 5 years .
The shelf life of a tire is the period during which it retains its performance when properly stored.
The end of this period does not mean that the tires have become unusable . A shelf life of 5 years is given by manufacturers because, by law, they cannot set a shelf life higher than the service life. Tires over 5 years of storage cannot be called damaged or defective, their technical characteristics may be slightly reduced.
American researchers argue that the period of storage of "shoes" must be at least 10 years. Experts from Germany are sure that it cannot exceed 6 years.
The expiration date of tires is the warranty period during which the manufacturer is responsible for the quality and condition of the tire if it was used for its intended purpose without violating the operating rules.
According to Russian legislation (GOST 5513, GOST 4754-97) , the service life of tires is 5 years from the date of manufacture.
How can I find out the date of manufacture of tires?
You can find out the age of tires by a special DOT code. Tires manufactured after 2000 in the DOT code contain two pairs of numbers, where the first pair indicates the week number of the year, and the second pair indicates the year. Earlier tires before 2000 have 3 numbers in their composition, where the first two digits are the week number, and the last one is the year (see the transcript in the photo).
Determination of the average shelf life of a tire according to GOST and operating conditions.
- The symbol ZR denotes tires for high-speed cars. They are recommended to be used at speeds over 240 km/h. up to 6 years
- Tires with the H symbol are used at a maximum speed of 210 km/h. within 5 years.
- The sign S symbolizes the maximum permissible speed of 180 km/h. and operational period of 4-5 years.
Most tire manufacturers do not agree that tire life is limited to 5 years. Each company has its own opinion on this matter. We analyzed several of them and the information they posted on their official websites.
Michelin
The French tire manufacturer Michelin has become famous for its active fight against the perception of the rapid aging of tires as a perishable product. Her information campaign "Tires Are Not Bananas" created a lot of noise in the automotive environment.
According to the representative office, several test trials were carried out in Saudi Arabia, South Korea and Germany. As a result of testing, no difference was found between new tires and tires stored for 3 years. They were tested for various characteristics such as rolling resistance, high speed durability, etc. Tires with a year life were approximately equal in performance to 10-year unused tyres.
Michelin focuses the attention of car owners on the fact that tires are not a perishable product, their shelf life is not as important as the service life is important, starting from the date the tires are installed on the rims. It is from this moment that the tire is subjected to all tests: pressure, temperature changes, wear, contact with uneven and sharp coatings, etc.
Continental
On the Russian official website of Continental, we found the following information on the expiration dates of tires.
“When a tire is stored in the correct position and under the recommended conditions, it will not lose its original balanced performance for 5 years from the date of manufacture of the tire.
A properly maintained, unused tire less than 5 years old can be sold as a new tire and used normally.
Continental recommends replacing all tires (including spares) with a sidewall date greater than 10 years.
Nokian
The following information is posted on the Nokian official website:
“Tire life is not defined by law, but tires can only be considered “new” if they have been manufactured within the last five years. The recommended service life of tires is six years and the recommended maximum period is 10 years.
The opinion of our specialists, based on many years of experience, coincides with the opinion of manufacturers: the shelf life is 5 years + the service life is up to 10 years. Moreover, more "adult" tires, in our opinion, are of better quality.
To keep tires as long as possible, they are stored in compliance with all rules and recommendations. The main condition is a cool, ventilated, darkened room away from oils, paints, ozone, and heat sources.
Rubber products tend to lose their performance over the years. To prevent and slow down this process, manufacturers add polymers to the rubber compound. They prevent oxidative processes that occur due to the interaction of protectors with oxygen and ozone.
The following are the main conditions for the proper storage of tires in accordance with GOST 24779-81:
Maintaining a constant regime without sudden jumps, slight temperature fluctuations from -30°С to +35°С are allowed;
Provide a low humidity level of 50-80% in a dry, ventilated cool room;
Avoid direct sunlight, use darkened hangars, shield heat sources;
Keep away from sources of heat;
Tires should not come into contact with corrosive, copper materials.
Avoid kinking, loading or positioning on an uneven surface.
Avoid contact with oils, organic solvents, acids, alkalis, fuels and lubricants on the tire surface. It is forbidden to lay tires on a wet and dirty surface.
In the warm season, when storing tires outside, they should be covered with light-tight material and raised above ground level to ensure ventilation and prevent the occurrence of the greenhouse effect.
Storage on reflective, light and heat absorbing surfaces is prohibited.
Keep away from chemicals, oils, paints, open flames, electric motors that produce ozone.
Used tires must be washed and dried.
Tires without rims should be stored upright.
The service life depends on many factors: the load on the car, the quality of the roads, the driving style, the distance traveled, tire damage, etc.
To increase their service life, follow these rules:
Check tire pressure every 2-3 weeks. With reduced pressure, tire wear increases by the equivalent of a % reduction. For example, a 15% reduction in pressure can result in a 15% reduction in service life. Inflated tires are less scary.
The wear of the front tires is always significantly higher than the rear ones, so it is recommended to swap them after some time, carefully watching the direction of the tread pattern and the direction of rotation.
Proper alignment of tires in relation to rims. If the direction is not the same, then performance is significantly reduced.
To prevent damage to the sidewalls of tires, avoid close proximity to curbs and high ledges.
Wash off dirt from the surface of the rubber and from deep grooves with special cleaning agents.
Adhere to an even driving style without harsh brakes and quick starts.
Do not overload the car beyond the norm. 20% excess weight leads to a 30% loss of tire life.
Keep the wheels balanced and check the alignment angles annually.
The main condition for a long tire life is:
- high quality products,
- careful operation,
- proper storage of tires in the off-season,
- timely diagnosis.
The age of tires in standard storage is a minor non-determining factor that should not be taken into account when buying them.
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How do you know when tires are completely worn out and it's time to change them? Everything is simple. For summer tires, the limit is 1.6 mm of residual tread depth, and for winter (or all-season, used in winter) - 4 mm. Modern summer tires can cover from 40,000 to 70,000 km depending on driving style and vehicle characteristics.
An average motorist rolls such a mileage on summer tires in 2-3 seasons. Moreover, wear implies not only a decrease in tread depth. For millions of cycles of deformation, the strength of the carcass and its adhesion to the layers of the rubber compound are violated. In short, every 2-3 years you should buy a new set of tires.
In case of irreparable damage to one of the tires and a relatively high total mileage of the kit, it is also worth considering replacing it. Well, or about buying at least a pair of new tires, which, for any type of drive, should be installed on the front axle. We put two tires back - the most decent of the remaining ones.
Many motorists drive only a few thousand kilometers a year. This does not mean that the tires will serve you for several decades. According to Russian requirements (GOST 4754-97), the service life of passenger car tires is 5 years from the date of manufacture. And for example, Continental recommends that all car tires (including the spare tire) older than 10 years old should be replaced with new ones.
Therefore, with small runs, you can navigate for ten years. The date of manufacture of the tire is indicated on the sidewall. Usually it is an oval with four numbers. The first two are the ordinal number of the week in the year, the last two indicate the year.
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Tires should be rotated periodically in accordance with the vehicle manufacturer's recommendations - information on this can be found in the owner's manual.
We can advise you to carefully use the tires and, most importantly, to store them correctly in the off-season. First of all, during storage, it is important to exclude direct sunlight from hitting the tires, which greatly age the rubber. Tires without rims should be placed vertically, and stacked on rims.
And before installing tires on a car at the beginning of the season, evaluate their condition.
There should be no cracks in the tread and sidewalls. The tire should not be dry, it should remain rubbery and not look like baked plastic.
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Winter tires have a much shorter life span. They almost always fail due to the wear of the treadmill, because the tread of a new tire is 7–8 mm, and only 3–4 mm remain working height. If the tires are studded, then with such wear there are very few metal elements left, and the tire will not provide adequate safety when driving on a winter road. However, not only spikes, but also Velcro, with such a degree of wear, also lose most of their capabilities.
The real life of winter tires rarely exceeds 30,000 km. "Bald" winter tires without studs can be re-rolled in summer, but their grip on hot road surfaces will be very poor. This must be taken into account, especially when braking.
