Liz grew up as a "grease monkey" to her father, who taught her to fix and work with many things. She also enjoys watching auto races.
Your Tires Talk
Surprising Things to Know About Tires
Did you know that:
- tires have a code that will tell you how old they are?
- the tire pressure stated on the tire is not the number you should use when inflating?
- there is just one time/situation in which you should check tire pressure?
- tire pressure is the number one most neglected maintenance item on the car?
All of the above statements are true, and we’ll examine them one by one. In the photo above, I've scraped white chalk over all this data, to make reading easier.
How to Read Your Tires
Among all the various numbers and letters stamped into the sides of tires, there is a set that is a code giving not only the date of manufacture but also the exact location of production. I was recently surprised to learn that the rear tires on my truck were made in Chile; the front tires were made in Canada!
Let’s get to reading that code, shall we? You need to look for the beginning of the code, which begins with the letters, “DOT.” That stands for Department of Transportation and is the certification stamp. Immediately following that will be a series of 11 to 13 numbers and letters. Within these letters is the code that tells the date of manufacture, by year and week of the year. It is the final set of numbers in the series.
For example, the series I found on one of my front tires (not the one in the photo) read as follows:
DOT B32K NM2X 2207
Ignore the first three letters reading ‘DOT.’ Look at the final four, 2207. That tells me that this tire was made in the 22nd week of 2007, or around the middle of May of that year. Hence, this tire is over ten years old.
To look up information on your own tires, you can go to the Tire Safety Group website, and enter your DOT data. It will even tell you, in bold red letters, if your tire is expired.
This Information Tells You the Age of Your Tires, and Other Things
Yes, indeed, they have actual expiration dates, though this is not part of any code you see on the tire, and it is not information the automakers or tire makers routinely tell you up front. The sad fact is that tires are only meant to have a lifespan of about six years!
This means the front tires on my truck are four years past their expected lifespan! Bummer! There is still at least 10,000 miles worth of tread left. However, it is the sidewalls that give way, and as many of us have sadly experienced, sidewall failures or punctures cannot be repaired; you have to buy a new tire! And that is exactly what happened with the tire I've pictured for this article. The photo below shows a very dangerous situation. Luckily, we caught it in time.
Newer cars will have the six-year figure buried somewhere in the owner’s manual, and in some cases, it will be on the driver’s side door sticker, but this is far from uniform.
A Dangerous Blowout Waiting for a Time and Place to Happen!
Whew! Got the Spare Installed in the Nick of Time!
Laws got Involved
Somewhere, in the well-intentioned effort to be “green,” and reduce landfill waste, and pollution from tire dumping, a law was made that tires need to be ‘biodegradable.’ Unfortunately, this law makes tire expire in those six-year periods, for they are supposed to start breaking down in 10 years.
Phooey! Guess what? That law seems to affect the sidewalls more than any other part of the tire. Whether they are made thinner, or of a different grade of rubber, I don’t know, but that is where they usually start giving out, and showing wear, many miles before the tread is worn. It seems such a waste, to throw out tires with so much tread left. I’m not sure these laws were well thought through.
Sometimes, you can find old, old cars, from the 1930s up through the 1960s or so, and the tires are still good. No sidewall cracking, and they still hold air. You’ll see this now and then, if you spend any time watching any of the numerous car-oriented TV shows, particularly the ones dealing with the restoration of antique cars, such as Chasing Classic Cars.
It used to be back then, that people would drive until the tread wore down, and the tires were ‘bald’ before they needed new ones.
So, unless you put very high mileage on your car with daily driving, you can expect to be buying new tires well before you think you should have to, judging just by the tread left. At today’s prices, this is not a pleasant prospect at all. Depending on your vehicle, you might have to take out a loan to pay for new tires. (Of course, I exaggerate, but it’s not far off the truth.)
Conveniently stamped on the tire is a number that tells you the pounds per square inch (psi) of air the tire will stand. Unfortunately, many people don’t also notice that it says, ‘maximum,’ or ‘max psi.’ This is the most the tire will safely hold and is not the number to use when adding air.
Inflated to the maximum pressure, the tire will actually be over-inflated, which leads to premature and uneven wear, and also causes handling problems—it is dangerous.
Under-inflation, on the other hand, leads as well to premature wear of the sidewalls, due to excessive flexing, and also causes drag and impairs gas mileage. The car will also be harder to steer, and feel sluggish. As I found out in my early driving years, a flat rear tire can make the car feel as if your engine is suddenly lacking power. The effect is that noticeable. .At least it was in the rear-engine car I had at the time. With under-inflation, the effect is similar but not as bad as with a flat. However, it still reduces your gas mileage. And with prices at the pump always creeping upwards, no one wants that!
Warning About Over-Inflation And Over-Loading
Maximum Load Statement
When Should You Check Your Tire Pressure?
There is just one time to check your tire pressure to obtain an accurate reading. That is when the vehicle is cold, having sat overnight, or parked for several hours. Driving, even with proper inflation, does have some friction with the road, (otherwise, you’d have no traction), and that friction produces heat. As we all learned in elementary school, heat causes expansion, and the air inside your tires is no exception. Ergo, a tire that has been driving for an hour or more, or even for as little as 15 minutes, will read an incorrectly higher psi.
One caveat here: if you live where summers are hot, you need to be up with the birds to check the pressure, for even a hot day will cause this same expansion, especially if the vehicle is parked in the sun. Figure approximately one pound of increase per hour of exposure.
According to experts in the automotive field, tire pressure is the most neglected thing on a car. Owners are aware of things like oil changes, and checking the level; they surely keep their windshield washer fluid topped off, and of supreme importance, the gas is kept filled up. But those poor lowly tires scarcely get a second glance, that is, until something goes wrong.
But My Car Has a TPM System!
Yes, cars made after September of 2007 do have a tire pressure monitoring (TPM) system installed.
However, these are no substitute for regular checking and maintenance on the part of the owner; they only kick in when the pressure drops very significantly, and there is already a problem, such as a foreign object embedded, causing loss of air.
Also, these systems are not standardized, and there are different types, and different levels of reliability. Don't let the presence of a TPM system lull you into thinking you don't need to worry about checking your tires!
Tires are the most important part of the car, after the engine, transmission, and brakes. They are your connection to the road; your ability to stop quickly. No matter how good your brakes are, tires that are worn won’t bring you to a stop in time to avoid an accident in an emergency.
Worn tires, especially those vulnerable and pesky sidewalls, are likely to cause a blowout. This can lead to loss of control of the vehicle with possibly deadly results. A front tire blowout at least leaves you steering control, but a rear blowout will throw you sideways, and maybe into a full spinout. In the worst-case scenario, traveling at freeway speeds, if you panic, oversteer, and hit the brakes, it will possibly be a rollover accident.
If you experience a blown out rear tire, do not touch the brakes! Just let the vehicle coast to a stop: turn on your signal to move to the side of the road (or use your emergency flashers), and steer very gingerly and carefully to make a safe exit to the shoulder.
Include your tires in your regular vehicle inspections and maintenance operations, along with checking the fluids. All of this should be done at minimum once a month. Your life depends upon those tires.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
© 2017 Liz Elias
Liz Elias (author) from Oakley, CA on June 23, 2018:
Hello again, C E! You got lucky! Those 'drive guard' tires, as you said, are only intended to get you to a repair shop. But, they do tout "up to 50 miles at 50 miles an hour." 50/50 gets a new meaning! ;-)
There are other names for this technology; one of them is "run flat tires."
I'm not sure of the science behind it, but be aware, it only applies to the treads.
Sidewall damage is another matter, and all bets are off!
May you enjoy many more miles of happy and safe motoring on your new tires!
C E Clark from North Texas on June 22, 2018:
What a great article! And very informative and usefu, which is of course the reason it's great. I learned a lot.
Just a couple of years ago I was driving on tires I'd had on my vehicle for 8 years. There were times when the tires looked low and one of them would sometimes look flat! One time the tire would look flat and the next time I looked at it, it seemed fine. I drove on it that way for the better part of a year I'd wager.
I bought those tires for my Christmas present, on sale, in 2007, and it was 2016 when I decided to stop by Kwik Kar and have one of the guys there check my tires out. They were Bridgestone tires purchased at Firestone and had something called Drive Guard built in (I still don't understand it very well because I haven't bothered to research it.)
Anyway, one of my rear tires had a slice or cut completely through the tire from one side to the other. It was almost like somebody had slit it, but the mechanics said it probably happened "naturally" because the tires were so old. Impossible to patch something like that. The Drive Guard had kicked in and enabled me to continue driving without issue.
Drive Guard is only meant to get you to the next repair shop, not through the next 10 months or longer and a few thousand miles. :0 That Drive Guard feature got some serious testing on my car.
I replaced all 4 tires after that inspection and the new ones have since been recalled and so I'm currently running tires that are only a year old. I had them checked just about a week ago because they were looking on the suspicious side, like my old tires had when I was driving on a flat for months. I recently drove on a city street full of rough railroad tracks and with sharp-edged holes big enough to swallow even an Escalade! Drove on it twice, and I'm amazed there's anything left of my 24-year old car let alone the tires!
Larry Rankin from Oklahoma on September 21, 2017:
Liz Elias (author) from Oakley, CA on September 19, 2017:
Yes, there is plenty of writing besides the big, bold proud brand-name imprinted. ;) The think is, it's semi-raised lettering, black-on-black, so hard to see in the first place, and even harder as the tires age and wear.
I don't think it applies only in the US; tires are made worldwide, and many of the same cars are sold worldwide, so I don't think it would be cost-efficient for the various manufacturers to make separate molds for different countries. But, that's just my opinion and guess; there's no telling what kind of idiotic wasteful practices today's corporations use! :-D
Mary Wickison from Brazil on September 18, 2017:
This is very valuable advice. I travel with my friend once a week and she has her tire pressure checked weekly. I didn't realize the pressure should be taken when cold.
I don't recall seeing writing on my tires but will look at them tomorrow. I wonder if that is only in the US.
Great information Liz.
Liz Elias (author) from Oakley, CA on September 18, 2017:
Goof for you, Eric; not many people think of that. Rotating those tires might be a good idea!
Liz Elias (author) from Oakley, CA on September 18, 2017:
Thank you very much.
Liz Elias (author) from Oakley, CA on September 18, 2017:
Right Bill, same with my dad. I had to know how to change tires and the oil before I could get my license! I learned a lot more than that, as well though, including how to disable a car if I didn't like the looks of the area where I parked. LOL! That I never used, as I wasn't likely to be in such places!
Eric Dierker from Spring Valley, CA. U.S.A. on September 18, 2017:
Quite informative. It makes me feel good knowing both our cars are topnotch in the tire department. I think I will rotate mine more often due to sun exposure on one side.
Bill Holland from Olympia, WA on September 18, 2017:
Amazing how many people in today's generation can't even change a tire. My dad wouldn't let me get my driver's license until I learned. :)
WheelScene from U.S.A. on September 18, 2017:
Great comprehensive article, thanks for sharing!