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Discussion Starter #1
Hi All

Some updates from 3 months ago a week after I purchased my 2019 Toyota RAV4 Limited and discovered my Tire Air pressure to be 28.5 psi in all 4 tires. I used my Intercomp 360060 PSI Glow Air Pressure Gauge and Accutire MS-4021 Digital Tire Pressure Gauge which are rated #1 by Consumer Reports and my JACO SmartPro Digital Tire 12V Portable Air Compressor to get all 4 tires back to 33 psi.

So I started checking every week in the early morning hours before using the SUV and discovered the pressure dropped by 0.5 to 1 psi in the 4 tires.

My final test which I completed this morning after waiting 3 full weeks to check my air pressure, I discovered all 4 tires to be at exactly 29.5 psi.

I have been reviewing tire reviews for both the Yohohama, Bridgestone, and Firestone tires the Consumer Reports, Tire Rack, and others rated the best from their testing. However the customer reviews varied greatly by their customer reviewers with complaints leaded by tires not lasting long, to poor mileage, noisy, poor wear, etc... None mentioned their air pressure or testing them as I have been doing. Most said they had their tires rotated every oil change with some mentioning theuse of nitrogen. I too complained about my Bridgestone Alenza and Firestone Destination LE 2 Tires I been using for over a decade on 3 different SUVs owned by my immediate family members, loved the tires but the 60,000 mile tires had to be replaced with even tread wear between 33000 and 38000 miles instead of the published 60,000 miles.

I just replaced the Firestone Destination LE 2 P235/70R19 tires on my wife's 2002 Jeep Liberty which only got 33000 miles, but they were the safest tire with little road noise and provided a comfortable ride so I replaced them with the same tire after the Firestone Service Center discounted them for me because of the poor lifecycle of the previous tires I bought from him. I forgot to mention I have been buying Bridgestones and Firestones from him for 30 years, get the lifetime alignment, and tire maintenance agreements, rotate tires every 6000 miles, but seldom checked my air pressure unless a tire looked low, feeling they checked it when they did the tire rotation, sound familiar to you all. So I did the same testing on the Jeep, I did on my RAV4 only to discover, the loss of air pressure was the same in the Jeep as in the RAV4.

Checked the air pressure in my Father in Law's new 2019 RAV4 Adventurer a month before me which has Continental tires and his was exactly 6.5 psi low in all 4 tires and no warning of a low pressure on his system.

My conclusions are that if you want your tires to last their longest, get the best mpg, and be less noisy you need to check and adjust the air pressure to what is on the door. If you want more comfort, you can lower the psi, but you sacrifice mpg and will have a little more road noise. As you drive on the highway for a long time, the tires heat up and psi increases which is why you get better gas mileage and less noise, but the ride may be a bit bouncy. Old dogs know these tricks, but seldom pass them down to the next generation. I remember my dad letting a little air out of his tires when it snowed rather than buy snow tires.

I hope the above experiences and my testing is beneficial to others purchasing Toyota Products with the OEM tires and making them last longer, and purchasing tires, I always use consumer reports, my experiences, and take reviews of others with a grain of salt.

Toyota recommends tire rotations every 5000 miles and oil changes every 10000 miles, most folks will wait till 10000 miles to do the tire rotation at the same time and this is a big mistake. I will use Toyota for the two year free maintenance checkup, but use my Firestone Dealer for non warranty after that since they are a lot cheaper than the local Toyota Dealer. I keep every Maintenance Invoice from Firestone to support any Warranty Issues should I have to argue should a part breakdown under warranty and they claim poor preventive maintenance on my part, which I never had that problem, and if I did, no problem filing a lawsuit. I work for the government and the name of the game is good record keeping of everything, no matter how small.
 

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I've owned various cars for over 50 years. Here's my experience...

1. All tires slowly lose pressure. They should be checked monthly (at least). It's safe to raise cold pressure to the max allowed on the tire sidewall (usually between 45 and 55). You'll get the best MPG but have a harsher ride. Modern radials will not wear out at the center. High-performance cars used to recommend 5 to 10 psi above the door sill sticker when running continuous high speeds.

2. The only tire rotation I've ever done is while the car is moving. However, because it was on Toyota's dime, I let my dealer rotate them (if he actually did) at 5K miles. IMHO, paying for this is a waste of money and time. The exception to this is AWD. Those systems like tire diameters to be identical. Of course, while checking tire pressure one can also check tread depth and then make a decision about tire rotation if differences are spotted. My RAV is FWD and I'll continue to let Toyota pay for it, then I won't bother.

3. I've tried Firestone and Bridgestone a couple of times. I didn't like them because their mileage life is way overrated. Continental has been good for me and they've had free hazard warranty for the first 12 months. Tire mileage warranties are pro-rated. You have little coverage as the tire ages.

Thanks for your research. It's a great way to get young folks aware.
 

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Discussion Starter #3

All Car Tires Lose Air Over Time: Find Out Why

All car tires lose air over time, and there are normal and abnormal causes for it.


The normal causes are:


  • Osmosis (permeation).
  • Temperature change.
The abnormal causes are:


  • Wheel parts damage.
  • Tire damage.
It’s important to check your tire pressure once per week/month. When a tire loses more air than 25% below the pressure recommended by the vehicle manufacturer, the tire-caused crash possibility increases threefold. Plus, if you drive on such a tire for some time, you may need to remove it from service as it would be considered flat.

Normal Reasons Why Car Tires Lose Air Over Time
Osmosis (Permeation)

Osmosis or permeation is the ability of air to pass through the structure of the tire rubber. It exits the tire at the rate of 1-3 psi per month. The exact air loss is usually determined by the model and make of the tire. Different rubber blends provide different rates of permeation.


About 1-3 psi per month is normal for air loss, but you still should check inflation rates often, and re-inflate your tires. Neglecting tire inflation for 6 months may take out 6-18 psi, and with the most frequent recommended rate being 30-35 psi, this is a big loss.


Some drivers prefer to fill their tire casings with nitrogen instead of air. The molecules of nitrogen are bigger, so they penetrate the rubber at a slower rate. However, there are pros and cons to this method.

Nitrogen vs oxygen molecules in tires

Image source: ricksfreeautorepairadvice.com

Temperature Change

Car tires lose air over time when the weather becomes colder – every 10°F drop in temperature removes about 2%. The inflation rate also rises by the same 2% with every 10°F temperature increase. In the US, the change between day and night temperatures may be about 20°F, so tires lose about 4%. So, if your vehicle was outside during a cold night, you may see a decrease by about 1-4 psi, depending on the recommended inflation rate. Don’t inflate the tire more in such a case, as the pressure will return to normal as it becomes warmer and the tire heats.


The theory that car tires lose air over time, due to temperature change, was proven, as shown in these tests.


The key thing to note is the amount of air in the tire is the same, even though the pressure gauge may show otherwise. When the temperature cools down, the air within the tire shrinks. In the same way, when the temperature rises, the air within the tire expands.


In winter though, tires should be re-inflated, as the difference between summer and winter temperatures can be about 50°F. Neglecting tire air pressure checks may sacrifice winter traction and handling.

Abnormal Reasons Why Car Tires Lose Air Over Time
Wheel Part Damage

Wheel part damage may create a hole for the air to escape the tire casing. There are two main kinds of damage that can become air loss causes: a poor valve stem or a bent/damaged wheel.

Poor Valve Stem
Cracked velve stem


Cracked valve stem

Valve stems may deteriorate, due to permanent chemical exposure, promoting air loss. They are the channels that allow us to fill the tire with air or deflate it if necessary. It’s usually recommended to change the valve stems whenever you buy new tires (about every 6-10 years).


However, it can be damaged earlier than that, due to harsh road conditions, hits, and bumps. If you tend to over-tight the valve stem cores after inflating your tires, this may also lead to air leaking. In order to avoid this, keep the torque at about 4 inches per pound. A pre-set wrench can help you maintain this.


So, if you notice your car tires lose air over time at the rate of more than 3 psi a month, you may need to replace the valve stems or their cores.

Bent/Damaged Wheel

A wheel that has partially lost its round shape will not hold the tire tight on it. Thus, the bead area allows some air out of the tire, and it may become flat in a couple of days or a week, depending on the severity of damage. A wheel may bend due to age, or after you hit a road curb or a pothole.


Corrosion is another factor influencing the rate at which car tires lose air over time. Especially if the rim corrodes on the edges where the tire is mounted. Damaged metal will become rusty and may cut the bead or make the surface it sits on become uneven, letting car tires lose air over time. So, if you notice the leak, make sure to run a full diagnosis on your wheels.

Corroded wheel bead seat.


Corroded wheel bead seat. Tire Damage

Tire damage will let air out directly, no matter how small it is. Some of the most common kinds of damage likely to cause an air leak are:


  • Nails
  • Bead damage.
  • Other road-hazard related damage.
Nails
Nail in a tire


Nail in a tire
A nail in the tire can let out about 2-3 psi daily. Even two days with such an air leak may make the tire’s performance much worse, or even make it dangerous to drive. If the nail stays in the tire tread, the loss of pressure will not be significant, but you shouldn’t leave it like that. While the tire is rotating, more pressure is put on the nail, and it can damage the tire further, causing a blowout.


A puncture from a nail is only reparable if it’s in the tread part of the tire. Any sidewall damage means the tire is no longer fit for purpose, and the repairs should be considered only temporary.

Bead Damage
Damaged tire bead


Damaged tire bead
Even the smallest space from the chunk of rubber in the bead area makes car tires lose air over time. Chunking usually develops as a tire ages, so it’s critical to know the date your tire was manufactured. You can find this out as it’s part of the DOT (Department of Transportation) code on the tire’s sidewall. The last four digits stand for the week and the year of manufacture. You can learn more on date codes from this article.


A piece of debris situated between the bead and the rim, can also let air out. Therefore, when driving on a surface with lots of debris, make sure to inspect your wheels and tires when the drive is over. By removing any foreign objects carefully, you will stop a leak from occurring and avoid rim and/or bead damage.

Other Road Hazard-Related Damages

Hitting a large road curb or pothole may damage a tire. However, multiple hits will most likely make car tires lose air over time. The sidewalls may flex, developing bulges, which means the air is trying to escape through the inner damage. If it succeeds when you hit another road hazard, the tire may blow out.


So, after every minor accident or a curb/pothole hit, check the tire pressure. Also, inspect the tire-wheel unit for any minor damage. Beware of cuts, bulges, and punctures, and if there are none, try to re-inflate the tire. If no air leaks, it means no harm was done. However, if you notice your car tires lose air over time (in a week, for example), consider driving to a tire shop for an inspection.

Tips to Maintain Proper Tire Inflation

These are some things you can do to avoid driving on underinflated tires:


  • Check pressure regularly.
    Some recommend checking pressure once a week, others prefer checking it once a month. You can choose depending on the roads you drive on, your driving style, and the type of your tires. If the roads are harsh and there are many curbs, or if you are a rough driver, inspect the tires more often. Furthermore, sports and performance tires are usually softer and have thinner sidewalls than off-road tires, so they also need more frequent checks.
  • Check air pressure on cold tires.
    All recommendations for tire pressure imply you pump the tires up when they are cold. This means the tires weren’t used in the past two hours (at minimum), or they are cool after a night in a garage. The vehicle also has to be in the shade if you want to check the pressure when the sun’s up. If you check the tires after more than 15 minutes of driving, remove about 1-2 psi from the rate you see.
  • Calibrate your pressure gauge.
    You can give your pressure gauge to a specialist at almost any tire station to calibrate it. This will help you get the most precise reading possible. Every psi is important for the performance and safety of your tires, and even new gauges may show +/- 3 psi before you calibrate it. So, when using a new or poorly calibrated gauge, you may not notice that your car tires lose air over time.
Recommended Tire Pressure Information

You can find the recommended tire pressure in your owner’s manual that comes with your vehicle. Also look at the door jamb to find information placard with tire size and inflation information. Make sure you read the right number, as there are both the recommended pressure and the maximum inflation rate at the maximum load the tires can carry.


Remember, tires will only perform well if they are of the same (or exceeding) load index and speed rating as specified on the placard. You can check all these specs on the sidewall of the tire as a part of its code.

Tire Pressure Monitoring System (TPMS)

Tire Pressure Monitoring System helps determine at what rate your car tires lose air over time. It’s preinstalled in every vehicle manufactured after 2007. The system will tell you whether one of the tires loses air more than the others, and when to check and inflate them. You will see the warning light every time one or all of the tires lose 25% of pressure.

Tire pressure monitoring system alarm


Image source: www.autoserviceprofessional.com
This survey shows how resentful some drivers are towards the TPMS. Only 58% of those surveyed can recognize the waring light of the system. 21% of drivers don’t want to rely on it and prefer to continue driving until they feel the damage themselves. Regardless, this system is recommended and fully approved by the National Highway Traffic Safety Administration (NHTSA).

The Importance of Tire Pressure

Some influences of car tires losing air over time are:


  • The tires’ load-carrying capacity.
    It’s not the tires what carries the mass of the vehicle, driver, passengers, etc. It’s the air within them that does, and the capacities are only working if there’s enough pressure in the rubber casing.
  • Tires’ lifespan.
    If there’s always enough air in the tire, it will perform better and last longer. Driving on under- or over-inflated tires causes uneven wear, which that may lead to blowouts, vibration, decreased life expectancy, and other issues.
  • Fuel economy.
    Proper tire pressure will reveal all fuel economy abilities of the tire. When the pressure is out of the ordinary, fuel consumption may increase by about 3%.
  • Your safety.
    Neglecting tire pressure checks causes about 75% of flat-tire issues.
Most passenger vehicles require a tire pressure of about 30-50 psi, while off-road vehicles may need about 80-100 psi. Following the 25% pressure decrease rule, a tire on a light car may become dangerous at about 23-39 psi, while tires on heavy vehicles at 60-75 psi. Considering, at this rate, the tires may be considered dangerous, keep in mind that every 5-7 psi matters for your safety. Therefore, the amount of air within a tire is highly important and needs your attention.
 

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Discussion Starter #4

When It Comes to Tire Pressure, Too High Is Better Than Too Low

Dear Car Talk

Dear Car Talk | Jul 20, 2017



Dear Car Talk:

My 2017 Toyota Tacoma calls for 33 pounds of air in all four tires. Where I live, during certain times of year, temperatures can range from a high in the 70s to a low in the 20s and back to a high in the 50s, all within two or three days. This makes tire pressure difficult to maintain. My question is: What are the safe high and low limits for tire pressure? I know if I go with 35 psi, I will have a hard ride and better gas mileage. If I go with 29 psi, I will have a softer ride and worse gas mileage. But for safety, when do I need to actually adjust it, in either direction? -- Gary



It's always better to go too high than too low with tire pressure, Gary (to a point).

As you say, tire pressure changes along with the outside temperature. For every change of 10 degrees in the outside temperature, tire pressure changes about 1 psi. So if you fill your tires to 33 psi when it's 75 degrees out, and it drops to 25 degrees at night, your tires will be at 28 psi. That's too low.

I've been told that most tire-pressure monitoring systems warn you when your tire pressure drops by about 10 percent. For you, 10 percent would be a little less than 30 psi.

Low tire pressure always is more dangerous than high tire pressure. When tires are deflated, more rubber touches the ground, the tires heat up and you're in danger of a blowout. If you remember the Firestone/Ford Explorer fiasco, the aggravating factors that led to many of those flawed tires exploding were heat (high road temperatures) and low tire pressure.

Higher pressure generally is not dangerous, as long as you stay well below the "maximum inflation pressure." That number is listed on each sidewall, and is much higher than your "recommended tire pressure" of 33 psi, Gary.

So, in your case, I'd recommend that you put 35 or 36 psi in the tires and just leave it there. You won't notice any difference in tire wear, handling or braking.

And even if the temperature drops 50 degrees, you'll still have 30 psi or more, which should keep your "low pressure" warning light turned off.

And if the temperature goes in the other direction, no harm will be done. As you say, at worst you'll end up with better fuel economy and a slightly firmer butt massage while you drive around, Gary.
 

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Discussion Starter #5
With respect to the Toyota RAV4 TPMS and the same air pressure problems I with my 2019 RAV4 consistent with Gary and hic 2017 Tacoma, my TPMS never gave a warning. I asked Toyota representatives when I should see a warning if the system is calibrated to 33 psi in all 4 tires? I was told by the dealer technician that I should have got a warning 29.5 psi, I had low of 28 psi with no light and even took it down to 25 psi for a test and no warning lamp. I contacted corporate more than once and received 10% from one person, 20% from another, and 25% from another. So I did temporary tests lowering the psi, until I got a warning lamp at 25 psi, that is 25% of the calibrated 33 psi set point and in agreement with the "All Car Tires Lose Air Over Time: Find Out Why" article as below


Tire Pressure Monitoring System (TPMS)

Tire Pressure Monitoring System helps determine at what rate your car tires lose air over time. It’s preinstalled in every vehicle manufactured after 2007. The system will tell you whether one of the tires loses air more than the others, and when to check and inflate them. You will see the warning light every time one or all of the tires lose 25% of pressure.
 

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Discussion Starter #6
under 4.5 General

Check " 2019 RAV4 VEHICLE SAFETY SETTINGS - TPMS - RADAR - CAMERAS - METERS " thread, I believe I discussed how to recalibrate your TPMS after you adjust your tire pressure in all 4 wheels.

If you set tire pressure to 33 psi, you will not see a warning until psi is 24.75, might be 24 or 25 psi on your hand gage dependent on its +/- 0.5 psi accuracy range. The maximum psi specification on the Yokohama AVID GT 235/55R19 tires is 51 psi.

One article mentioned if you lose 1 or 2 psi per week, readjust your tires specified for 33 psi to 35 psi, it will improve mpg and lower road noise and not impact comfort all that much and remember to recalibrate your TPMS for 35 psi, this will reset the TPMS warning lamp to 26.25 psi for low pressure and 43.75 psi for high pressure warning, well under the 51 psi maximum. The psi increases on highway the most caused by heat, the lower your psi, the more the tires heat up as will the psi increase. Lastly, for every +/- 10 degree of temperature change outside your psi changes +/- 1.0 psi respectfully as a rule of thumb. So if you are driving on the highway in the South this time of year on a long trip leaving in the early morning hours to evening hours you can expect possible changes of 10 to 30 degrees or vice versa PM to AM.
 

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My experience with tires after more six decades of driving and especially since tubeless tires became the norm is that new tires tend to lose some pressure until they have been "broken in," generally for a few months after installation, probably from increased flexing and a resulting slight increase in size and hence inflation air volume. I check the pressure on our vehicles once each month. After the initial period of use the difference from month to month with the same temperature conditions the pressures generally are only i/2 psi lower than the previous month's reading - insignificant.

One can possibly 'overthink" the issue of tire pressure and then overreact.
 

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Discussion Starter #8
My experience with tires after more six decades of driving and especially since tubeless tires became the norm is that new tires tend to lose some pressure until they have been "broken in," generally for a few months after installation, probably from increased flexing and a resulting slight increase in size and hence inflation air volume. I check the pressure on our vehicles once each month. After the initial period of use the difference from month to month with the same temperature conditions the pressures generally are only i/2 psi lower than the previous month's reading - insignificant.

One can possibly 'overthink" the issue of tire pressure and then overreact.
Jim

It all depends on how much time and money you want to spend and waste. More than 50% of consumers complain they get much less tread life on their tires than the manufacturer rates them for. Most folks are ignorant to the reasons why and what they can do about it besides shift to another tire manufacturer and blame that one for over rating their tires. There are a large percentage that get the full life value and a real small group that exceed the rating for some reason.

I follow consumer reports on the tires they test and rate in the upper echelon and I buy those tires. If they say it is good for the manufacturer rating, then I blame myself for the reasons why and look at some of the causes to correct. The above threads point out those flaws.

You must be in your 80s having been buying tires for m ore than 6 decades, as I am a youngster at 65 years old. However I am an engineer for the past 40 years and been working for the US Navy. I purchase off the shelf materials, equipment, and systems and apply it all to a US Naval Ship environment. Installation and Preventive Maintenance are very important in the military which I follow up on with better operating, installation, and maintenance procedures than the manufacturers provide. I provided training to thousands of operators, technicians, and engineers in my lifetime yo perform their functions to extend system life to its fullest. As a result, the systems I am expert in are replaced every 10-15 years at which time the internal parts are out of production and/or annual maintenance costs have exceeded 40% to purchase new with new warranties. For this effort, I feel I am protecting the taxpayer's investment, like you and me. Retiring next year, so I can spend more time with my own household.

Bill
 

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I must have super tires. Over 3K miles, some temp changes (90s to 30s) and two months of owner ship my tires have lost a GASP pound of air. So instead of 37 they were 36. I better hurry and replace that 1 pound because its the end of the world otherwise. Oh and I have that "nasty" normal world air in my tires.

I am not an engineer but I did, however, stay at a Holiday Inn Express.
 

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Getting ready for another long trek so I checked my tires today. They were down to 35 from 40 (about 4 weeks ago). The current temp was 65, down from 90 (about 4 weeks ago). I raised them to 42.
 

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Discussion Starter #11
Numbers

I am raising mine from 33 to 35 for same reason, shame we don't have the Colonel's great tires huh
 

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Yeah, I have not had issues with super leaky tires without a mechanical problem. I usually pay attention to them after the first real cold snap where there is consistent temperature change. Then I just check them here and there and don't have issues with big pressure loss.

Mine sit in a garage and I use my compressor to fill and the vehicle has not been driven. I usually do it in the morning when the vehicle has been idle all night. Ambient temp of my garage is between 60-85.
 
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