More than a few of us have spent time looking for the placard with a vehicle’s tire pressure recommendations. And more than a few consumers have looked at their owner’s manual or that elusive placard and wondered why the pressures there are different from the maximum pressure on the tire’s sidewalls.
How do the automobile manufacturers and their tire suppliers come up with those numbers?
It starts with the load the vehicle is designed to carry and the size of the tires installed on it. Worldwide, several organizations exist with the primary purpose of establishing and publishing interchangeability standards for tires, wheels, valves and allied parts.
In the U.S., this standardizing body is the Tire and Rim Association (TRA). Its European equivalent is the European Tire and Rim Technical Organization (ETRTO). The Japanese Automotive Tire Manufacturers Association (JATMA) has that respon-sibility in Japan. There are other similar organizations, but those three are the major players.
None of the major standardizing organizations is government mandated or regulatory. The organizations, and the standards that they set, are all voluntary. There is no legal obligation for any tire or auto manufacturer to abide by the standards. However, for practical and legal liability purposes, it simply makes sense to follow the standards and all vehicle and tire manufacturers use them.
While TRA, ERTO and JATMA all use slightly different protocols, they consult with each other and their standards are all very close. These organizations establish a range of standard dimensions for each tire size so that the proportions of all tires of a particular size are very similar. This assures that all tires of a specific size are interchangeable, at least in terms of their physical dimensions.
They also set each tire’s “load curve,” which is the relationship between inflation pressure and the tire’s maximum load carrying capacity. Like the size standards, there are some slight variations among the different organizations’ load curves, but they are not significant.
Part of each load curve standard is the point at which the load curve stops going up. For TRA p-metric standard load tires, it is at 35 psi. Equivalent ETRTO and JATMA tires peak at 36 psi. Interestingly, all of the standardizing organizations agree that standard load passenger car tires can (and should) use optional higher inflation pressures (44 psi or 51 psi) for certain circumstances such as high speed driving. However, these higher inflation pressures generally provide no increase in load carrying capacity and in some circumstances specify a reduction in load for high-speed use.
So the auto manufacturer knows what a vehicle weighs and knows how much weight can be added in fuel, passengers, cargo, etc. They can look at the load curve of the particular size that they have selected. To this number, auto manufacturers usually add a safety factor of around 10%.
For passenger cars, SUVs and light trucks, the load curve number launches a series of negotiations.
The engineers responsible for the vehicle’s handling are likely to lobby for additional inflation pressure to improve handling. Similarly, lower rolling resistance results in better fuel economy and leads to demands for higher inflations. Cars likely to see high-speed bring with them engineers insisting on more air pressure. On the other hand, ride considerations are an important consideration and that calls for lower inflation pressures.
Today, the results of these nego-tiations are inflation pressures typically in the 32 psi to 35 psi range. If the champions of improved ride had their way, the 26 psi to 28 psi range that was common a few years ago would be more common. The safety factor of the higher inflation pressure seems to be carrying the day with automakers. After all, no one wants a repeat of the fiasco of when Ford set the recommended pressures on first generation Explorers at 26 psi.
In that situation, recommended inflation pressures too low to provide an adequate safety factor were frequently combined with poor maintenance, overloading and high ambient temperatures to produce a series of often-deadly accidents (250 deaths and 3,000 serious injuries were attributed to the problem).
Other factors keep the process of determining recommended pressures from being completely cut and dried.
Aesthetics is often a big factor when automakers choose tire sizes, and the emphasis on style versus substance can complicate the negotiations. The popularity of extreme low-profile tires has required significant increases in recommended pressures. Cars likely to see significant high-speed often force auto manufacturers to lower load limits, move to higher tire speed ratings such as W or Y, or go to recommendations of up to 51 psi.
Although the process starts with load and seems like it would be simple, nothing is etched in stone.
The recommended pressures go onto the vehicle’s tire information placard once the engineers make their final decisions. Beginning in 2003, federal regulations required automobile manufacturers to place tire information placards in a standardized location and follow a common format. The tire information placards identify the OE tire sizes and inflation pressures (including the spare), along with the vehicle weight capacity.
All new vehicles must now have a placard located on the driver’s side doorjamb (the B-pillar). If a vehicle does not have a B-pillar, then the placard is to be placed on the rear edge of the driver’s door. And if the vehicle does not have a B-pillar and the driver’s door edge is too narrow, the placard is to be affixed on an inward facing surface next to the driver’s seating position.
In addition to providing the OE tire size(s) and recommended inflation pressure(s), vehicle manufacturers must also identify vehicle load capacity with the following sentence: “The combined weight of occupants and cargo should never exceed XXXX pounds.”
For vehicles produced between 1968 and 2003, the original tires size(s) and inflation pressures were listed on a placard usually found on the driver-side door or doorjamb, rear passenger doorjamb, fuel filler door, glove box or center console door or inside the engine compartment.
Sometimes alternate pressures based on load or speed conditions are also provided.
Consumers are often confused because federal safety regulations also require tire sidewalls to contain information about a tire’s maximum load capacity and maximum inflation pressure. For P-metric standard load tires, the maximum pressure listed on the sidewall will be 44 psi or 51 psi, even though the pressure where the maximum load occurs is 35 psi or 36 psi. On the sidewall, this would look like “Maximum Load XXXX lbs. Maximum Pressure YY psi.”
A few manufacturers interpret the regulation to mean the maximum load and the corresponding inflation pressure (“Maximum Load XXXX lbs. at YY psi”). Either way, too often consumers see the maximum inflation pressure on the sidewall and believe that is the correct pressure for their car.
Look at some of the online forums and you will see that the arguments about relying on the placard or the tire sidewall can be animated.
Regardless of the information on the tire sidewall, assuming the right size tire is installed on the vehicle the placard is the correct information.
While the maximum load of the vehicle is the primary factor in establishing the recommended pressures, many other considerations went into the calculations. Don’t make changes lightly. Varying from the vehicle manufacturer’s recommendations requires careful consideration of why you want to make the change and the possible safety implications.
In this article:tire technology
Maintaining proper tire inflation is relatively simple and essential to the overall tire performance of your vehicle. A properly inflated tire will provide longer life, quicker steering response, better fuel efficiency and a smoother ride than an improperly inflated tire. Both underinflation and overinflation can cause headaches like premature treadwear and possible tire failure. The best way to ensure you're getting the most out of your tires is to check your tire pressure on a monthly basis.
Knowing how to use a tire pressure gauge is very simple.
Here’s how to check tire pressure and refill your tires.
Items You Need When Checking Tire Pressure
Tire pressure gauge
Air compressor
Pen and paper
Your tire pressure gauge can be digital or standard. Auto parts stores typically carry both. Many auto parts stores sell portable air compressors that run from your car battery or 12v power port. Alternatively, you can use the air compressor found at most gas stations. They usually cost $0.50 or $1.00 to use.
Vehicle manufacturers specify PSI – literally “pounds per square inch” of pressure – assuming tires are cold. Tires are considered cold when the vehicle has been parked for three hours or more, or if the vehicle has been driven less than a mile (1.6 km) at moderate speed. PSI is the unit your pressure gauge uses to provide readings.
Look on the driver’s side door jamb or your owner’s manual to find the recommended cold tire PSI for your front and rear tires.
If you cannot find it, you should consult your vehicle dealer, manufacturer, or a qualified tire professional.
If your front and rear tires require different pressure levels, write down the correct PSI for each to avoid getting confused as you move around your vehicle checking tire pressure.
Remove the valve cap from one of your tires. Then place the pressure gauge on the valve stem and press down hard enough so the hiss sound disappears and your gauge provides a reading. With a standard gauge, the air pressure will push a small bar out from the bottom of the gauge. Measurement units are etched into the bar. A digital gauge will show you the reading on a screen.
Write down the reading and repeat this process for all four tires.
Use an air compressor to refill any tires with low pressure. Many air compressors are different, so read directions carefully to be sure you’re using it correctly.
If you’re using the air compressor at a gas station, be sure to park so that the hose will reach all four tires. Insert change into the machine until you hear the motor running. Fill each tire by placing the end of the hose over the valve stem and pressing on the lever.
Using a gas station air compressor means your tires might be “hot.” If it is necessary to adjust inflation pressure when tires are “hot”, set their pressure to 4 psi (14 kPa) above the recommended cold inflation pressure. Recheck the inflation pressure when the tires are cold.
After filling your tires, use the gauge to check pressure again. At this point, it’s ok if you overfilled the tires because you can always let some air back out. Never drive on overinflated tires. Overinflation can result in decreased traction, premature wear, and decreased impact absorption.
Make the above procedure a monthly ritual. Regularly checking your tire pressure is the best way to ensure your tires never dip far below the optimal PSI.
Accuracy matters and you should keep that in mind when choosing a gauge. For just a few dollars, you can find a quality, accurate tire pressure gauge that gives accurate readings. If you’re not sure which one to purchase, ask a professional technician which he or she prefers.
A digital tire pressure gauge will provide accurate readings, but don’t forget that it operates on a battery. If you think having to replace the battery will prevent you from using it, it’s best to go with a standard gauge.
It’s best to use your personal tire gauge versus those available attached to air hoses at service stations. Of all the pressure gauges out there, they’re the most likely to be weathered, and possibly inaccurate.
There’s never a good time for a flat. That’s why Bridgestone DriveGuard tires are masterfully engineered to keep you moving for up to 50 miles at speeds up to 50 MPH without disruption.
There’s never a good time for a flat.
That’s why Bridgestone DriveGuard tires are masterfully engineered to keep you moving for up to 50 miles at speeds up to 50 MPH without disruption.
See Details Find Your Fit
What should be the pressure in the tires of the car? Does it need to be adjusted and what will happen if the pressure is changed in one direction or another?
Two friends conversation:
- Hello, I lowered the wheel!
— Absolutely?
- No, only from below ...
Humor from the Web
Let's start with platitudes. The pressure must be as specified by the vehicle manufacturer. And since the average modern driver usually does not have such information, especially for him, a "cheat sheet" with the necessary numbers is hung on the middle pillar on the driver's side or on the gas tank hatch cover.
A relatively rare solution: the "reminder" is located on the gas tank cap.
A relatively rare solution: the "reminder" is located on the gas tank cap.
An important point: pressure should be measured only on cold tires. By the way, especially for pedants: cold tires are those on which the car has been without movement for at least 5 hours.
This "cheat sheet" nestled on the driver's door. An example of how tire pressure recommendations change depending on tire size.
This "cheat sheet" nestled on the driver's door. An example of how tire pressure recommendations change depending on tire size.
Since car manufacturers allow the use of tires of different sizes, the pressure may also be different. In addition, the pressure in the front and rear tires has the right to both differ and be the same.
And here there is no difference in recommendations: what is in front, what is behind is the same.
And here there is no difference in recommendations: what is in front, what is behind is the same.
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Reduced pressure leads to an increase in tire deformation, more heating during wheel rolling, accelerated wear of the outer tread tracks. Perhaps even a violation of the integrity of the frame. As a result, fuel consumption increases. If you hit a hole in the road, the likelihood of damage to both the disk and the tire is higher.
Increased pressure is an overstress of the cords, increased wear of the middle part of the tread. In addition, when driving on a bad road, the shocks that are transmitted to the suspension and body will become more noticeable for riders.
When hit in a pit, the likelihood of a tire burst increases.
Uneven pressure on all four wheels is the worst thing! At the same time, the car, while driving, inevitably leads the wheels with lower pressure to the side - in fact, sideways movement begins.
Tube tires of the past required a weekly check, especially before the advent of butyl tubes. Then the pressure began to be checked less often, and nowadays, as a rule, they are limited to visual inspection.
Tube tires of the past required a weekly inspection, especially before the advent of butyl rubber tubes. Then the pressure began to be checked less often, and nowadays, as a rule, they are limited to visual inspection.
In a good way, you need to check the tire pressure at least once a month. And before a long journey - just a must.
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Budget Tire Compressor Test: Wrong Bees
The air pressure in an enclosed space changes by approximately 0.
1 bar for every 10 degrees of temperature change. This allows, having installed summer wheels in April, not to worry about the pressure in them until the end of August, when the air temperature begins to drop. Having pumped up the wheels at the end of summer, you can already reach the seasonal shift. But having installed winter tires in October, with the first frosts, you should check the pressure a couple more times: when the temperature drops to minus ten, fifteen, and when it goes over minus twenty. But from the middle of winter until the moment of changing the wheels to summer ones, there is again a period of relaxation.
Electronics are increasingly thinking for us. Now, a tire pressure monitoring system is being installed on parts of production cars. Moreover, some simply read the wheel speeds through the ABS sensors: after all, a flat tire rotates faster, since its radius is smaller than that of inflated wheels. There are also sensors that evaluate the amount of air pressure and send information via radio to the "brains" of the car.
Such devices can also be purchased separately: sensors - in the wheels, and the receiver - in the car.
By the way, a lot depends on the road you are going to take.
The operating instructions supplied with the vehicles indicate that it is recommended to increase the pressure by 0.2-0.3 bar before driving for a long time on expressways. We advise you to follow these recommendations on all cars: it will not get worse.
The operating instructions supplied with the vehicles state that it is recommended to increase the pressure by 0.2-0.3 bar before driving for a long time on highways. We advise you to follow these recommendations on all cars: it will not get worse.
I don’t want to discuss overload: this, you see, is not the case. But, unfortunately, many deliberately overload the car several times a year, not only stuffing the interior and trunk to the eyeballs, but also attaching a trailer, which additionally loads the rear wheels of the tractor.
In such cases, we advise you to increase the pressure in the rear tires by at least 0.2–0.3 bar. Tires will only thank you.
If you doubt the accuracy of your pressure gauge, then we advise you to check it immediately after leaving the tire shop, where you were set the obviously necessary pressure, to measure it with your own measuring device (separate or as part of the compressor). So you determine whether your pressure gauge is "lying" a lot. For the future, right on the dial, you can put a mark of the correct value.
Of course, it is better to have your own, known to be correct pressure gauge, but such a toy is not cheap.
Of course, it is better to have your own, known to be correct pressure gauge, but such a toy is not cheap.
If terrible ice caught you on summer tires, say, in the country, and you need to drive some distance along an absolutely icy road by any means, then you should reduce the tire pressure to approximately 1.
6 bar. Is it bad for tires? Yes. But an accident will cost more. In addition, in such a situation, one does not have to wait for high speed, and overheating of tires at near-zero temperatures most likely will not happen.
Everyone knows what caused the excellent maneuverability of Soviet tanks? That's right: wide tracks, that is, low pressure on the ground. We, having an ordinary, non-all-wheel drive car, are also able to provide it with a similar cross-country ability. If the wheels of the car sink into sand, snow or sticky mud, then it makes sense to lower the tire pressure. And not only driving, but also driven wheels.
We know from experience that you can often get out of the "black spot" by reducing the pressure to 1.2 bar.
We know from experience that it is often possible to get out of the "black hole" by reducing the pressure to 1.2 bar.
In a very critical situation, if you know that you have a fairly narrow disc and a relatively wide tire (such a wheel has a lower chance of self-disassembly), you can reduce the pressure to 1.
0 bar.
Stalled on wet grass? Try to relieve pressure.
Stalled on wet grass? Try to relieve pressure.
Pressure reduction is also useful in other cases - for example, to overcome diagonal hanging. If you reduce the pressure in the wheels on which the car rests, their height will decrease and there will be a chance to “hook” on the suspended wheels. Of course, if the car has already laid down on the bottom, then it is too late to reduce the pressure - this will only get in the way.
A concrete example of the effect of pressure on flotation. In this case, the pressure is very low, and the contact patch of the wheel with the coating is much larger than that of a conventional car.
A concrete example of the effect of pressure on patency. In this case, the pressure is very low, and the contact patch of the wheel with the coating is much larger than that of a conventional car.
In general, the pressure in tires, as well as in vessels, is better to keep normal. Any deviation has its negative consequences. Tell us, have you ever had to adjust tire pressure to improve flotation?
Tire pressure: your norm
Tire pressure: your norm
See also
Tires are the only vehicle element that is in constant contact with the road. One of the main indicators of their serviceability is pressure. It affects not only fuel efficiency, but also safety.
As a rule, car manufacturers recommend maintaining tire pressures between 2.0 and 2.8 bar. But in practice there are situations when it is necessary to deviate from this norm.
adv.
rbc.ru
Tire pressure should be checked at least once a month, there are several ways to do this. We understand why it is so important to observe the optimal pressure indicator and what it affects.
In this story:
Tire pressure is the resistance with which air "presses" on the inner area of the rubber. Properly inflated tires will last longer, give you better ride quality and improve your driving safety. If the pressure in the tires is too low or they are pumped over, then the car owner runs the risk of facing a number of problems: from buying new tires to the threat of an accident.
Properly inflated tires will last longer (Photo: Global Look Press)
Under-inflated tires are tires that are below the recommended pressure.
In this case, the contact patch of rubber with the road increases, which leads to increased friction or rolling resistance. A worn out outer edge of the tread can visually give out such a problem.
Increased friction with the road can cause the tire to overheat, slip and even burst. In addition, low tire pressure leads:
When tires are over-inflated, that is, above the manufacturer's recommended rate, the contact patch decreases. As a result, the main friction with the road is taken over by the central part of the tire.
Excessive tire pressure leads to excessive sensitivity to road irregularities and the risk of tire damage, even destruction. Inflated tires also cause the following:
For overinflated tires:
Excessive tire pressure leads to excessive sensitivity to road irregularities and the risk of tire damage (Photo: Shutterstock)
For each car model, the manufacturer sets its own optimal tire pressure. This indicator depends on the mass of the car, the speed of operation, the number of passengers (partial or full boarding), as well as the load on the trunk [1].
The recommended tire pressure can be found in the vehicle owner's manual or on one of the plates/stickers in the passenger compartment. They can be:
Tire pressure is measured in several units. In Russia, they usually indicate in kg / cm 2 (or atmospheres) and bars (bar). These two indicators are almost equal, which is why they are often used as synonyms:
Foreign models often use pounds per square inch (pound per square inch), or psi:
For convenience, car manufacturers can indicate pressure in two units at once - bar and psi. Thus, the need to independently calculate according to the formulas disappears. Otherwise, you can do this in one of the online calculators or check the table of popular values.
| 2.0 bar | 2.1 bar | 2.2 bar | 2.3 bar | 2.4 bar | 2.5 bar | 2.6 bar | 2.7 bar | 2.8 bar |
| 29psi | 30psi | 32 psi | 33 psi | 35 psi | 36 psi | 38 psi | 39 psi | 41 psi |
Temperature has a significant effect on tire pressure: when it drops, the pressure in the wheels decreases with it. When the temperature drops by 10 °C, the tire deflates by an average of 0.07–0.14 bar or 1 to 2 psi [2].
Temperature has a significant effect on tire pressure (Photo: Shutterstock)
Summer tires typically use manufacturer's recommended readings.
But in winter, it is advised to add about 0.2 bar to these figures [3].
Experts also recommend checking and correcting tire pressure at outside temperature. In the cold season, swapping is best done not in a warm garage, but on the street. In summer, before such a manipulation, you should make sure that some of the wheels of the car were not under the scorching sun, while others were in the shade.
Sometimes the tire pressure needs to be adjusted according to the situation. For example, when the machine is fully loaded or a trailer is towed. For such cases, automakers, as a rule, separately indicate the optimal pressure.
But there are moments that fall into the category of extreme and non-standard (especially if before that the car most often drove around the city). Automotive expert Tatyana Eliseeva analyzed the most common of them.
Causes tires to heat up, especially in summer, so you should follow the manufacturer's recommendations before such a trip.
We do not know what we will meet: patched road repairs or heavy rain. After all, for each of these situations, the recommendations will be opposite. Athletes can play with pressure when track conditions are known and engineers can always change the settings. For a long journey, the layman just needs to choose the average.
Tires must be bled off, especially on sand. The question is for how much? You can bleed up to 0.7 atm, but a not very experienced motorist can slip the wheels with an inaccurate movement, and if the driver turns the steering wheel sharply (for example, trying to catch on the edge of the track), then the tire can come off the disk. And such cases occur regularly.
At near-zero temperatures on packed snow, ice or sludge for new wheels (velcro or studded) it is better to pump the wheels a little so that water and sludge are squeezed out of the central zone of the contact patch and the tread is better worked.
The wheel must be cleared for the tread to work. When it is clogged with snow, the braking distance and traction deteriorate greatly.
If the car has worn wheels, but with an acceptable tread depth for winter tires (4 mm), then you should not hope for the correct operation of the tread. Such a low checker no longer pushes the snow. In this case, it is necessary to reduce the pressure in the wheel, thereby increasing the same contact patch.
Photo: Global Look Press
On a country road, the weight of the machine will be an important factor. In this case, we select the pressure according to the load - specific indicators must be viewed on the central pillar of the body. There you will see something like the following recommendation: the more the car is loaded, the higher the pressure in the rear wheels should be.
But a badly broken road can lead to herniations, ruptures and tire damage. Therefore, if we increase the pressure, then we drive on a bad road as calmly and measuredly as possible.
Or we slightly deviate from the manufacturer's recommendations and raise the pressure not as much as the manufacturer recommends.
The main factor in changing the behavior of the wheel is not the pressure difference at altitude, but the presence of a large number of sharp turns and long braking. The tire will heat up not only from the loads, but also from the operation of the brake mechanisms. Therefore, the idea that due to low pressure it is necessary to increase the pressure in the tires is wrong, because the temperature of the wheel has a much greater influence in this case.
The recommended pressure is always given when the tires are cold. This means that the vehicle has not been driven for three hours or has traveled less than 1 mile (or one mile).
There are two ways to check tire pressure: on your own or at a workshop. In the first case, it is enough to use a public pump at a gas station or purchase a pressure gauge.
This tire pressure measuring device comes in three types:
Another option is to install special pressure control caps on each nipple. Such a gadget works as follows: the upper part of the cap is transparent and, depending on the level of pressure, an indicator of three colors appears in it. Green - the pressure is normal, yellow - the tire is flat, red - the pressure has exceeded the norm.
Photo: Shutterstock
The easiest way to monitor tire pressure is with the automatic TPMS (Tire Pressure Monitor System). Today it is installed on almost all models, and in some countries its presence is a prerequisite for releasing a car from the assembly line.
In these systems, the electronics automatically detect changes in the tire, and if the pressure drops below the recommended value, a warning signal lights up on the on-board computer screen.
There are two types of TPMS:
Car manufacturers recommend checking tire pressure every two weeks, but at least once a month. Indeed, even under ideal conditions (for example, the car is idle for a long time), the wheels lose approximately 0.069bar, or 1 psi, per month [4].
The pressure should be monitored before and after a long trip, during a sudden change in temperature (for example, during the first frost or warming), and also after changing tires or driving with a load.
