What To Know About Tires and Safety

Just give this a moment’s thought. The only thing between your car and the road at any given moment are four pieces of rubber, each no larger than the palm of your hand.

Even more, if anything goes wrong with any one of those pieces of rubber – you and your car aren’t going anywhere. That is if you’re lucky. If your luck runs out, a tire failure can mean an accident, an injury or even death.

If there are any two areas where a driver simply has no margin for error when operating a vehicle, it’s the brakes and the tires. Fool around with either one of these, put off regular maintenance and upkeep, and you can find yourself in a world of hurt.

Of these two, brakes and tires, at least the brakes usually give some warning before they fail. They’ll make noises, you’ll feel your auto’s stopping power diminish, or notice unusual bucking when coming to a stop.

With a tire goes, one moment you can be riding along without a care in the world, the next comes the catastrophic failure.

Let’s explore the major reasons for tire failures, and what you can do to mitigate or stop any damage before it happens.

Under-inflation

One common cause of tire failure is under inflation. Every tire has a recommended range of safe air-pressure that should be observed and maintained.

If a tire is under-inflated, the increased friction with the road builds up both stress and heat within the tire’s materials. Too much and too long, and you end up with a blow-out. If that blow-out happens when you’re travelling at highway speeds, you can easily lose control of the vehicle.

The solution is straightforward: Buy a tire pressure gauge and check those tires!

Please remember – your auto tires can lose anywhere from a quarter pound to a full pound of pressure every month. This is normal, and unavoidable. (Well, it can be somewhat avoided by inflating your tires with pure nitrogen. Since nitrogen molecules are larger than the typical normal-air mixture, they migrate out at a slower rate. But when was the last time you saw a nitrogen-air refilling station?)

Over-inflation

Too much air pressure is also dangerous. As your car moves down the highway, temperatures in the tire rise, which increases the air pressure inside the tire. Past a certain point, the pressure can reach a critical mass and blow a hole through the tire’s weakest point.

The result is the same as above, you lose control and can be involved in a serious accident.

Worn Treads

Here’s another cause of accidents which are almost always preventable – driving with tires that have lost their treads. Every time we drive, we leave some of the tire behind. In fact, Firestone Corporation once estimated that 600,000 metric tons of worn-off tire rubber are lost on our roads every single year.

Why are worn treads so dangerous? Two main reasons.

  • The first is that it’s an indication the total amount of rubber in the tire has decreased, making it far more likely a puncture will penetrate through the tire. Since there is less material between the compressed air and the outside world, failure is more probable.
  •  The second reason is because the treads themselves are important in their own right. Without them, our autos would hydroplane at the slightest provocation. The treads channel water, oils, dirt, grime and even air from the road and the rubber – keeping our vehicle going straight and not floating and twirling along the pavement like a ship at sea.

In perfect and dry conditions, a smooth tire may perform well. (Just look at those racing car tires!) But we almost never have perfect and dry conditions on our roads. Thus we need those treads.

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How much tread is considered safe?

Automobile tires have reached the end of their useful life when only 1/16″ (1.6mm) of the tread depth remains. When only this much remains, you need new tires. You can do a quick test by using the “penny method.” Take a United States penny, and place the cent with Lincoln’s head down between the center threads.

  • If the penny goes down to the forehead or beyond, you should be OK.
  • If you can see partial hair, it’s time to start tire shopping.
  • If you can see all the hair, stop whatever you are doing and buy new tires!

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Sidewall Damage

We’ve all done it – scraped the tires along a curb or hit a nasty pothole. We usually don’t give it a second thought. But do it often enough, or the bump or scrape is severe enough, the tire can lose its outer wall integrity, with a side blow-out being the unfortunate result.

If you ever notice any bulges in the side of your tire, replace the tire immediately.

Proper Wheel Alignment, Rotation and Tire Balancing

While not absolutely critical, these three issues – alignment, rotation and balancing – do effect the smoothness of your drive as well as how long your tires will last.

  • Alignment: Misaligned tires can wear out faster on one side than another. So for instance, while the right side may have viable treads, the left side may have little or none.
  • Balancing: Balancing your tires has a similar effect – making sure the wheels don’t wear out unevenly. Improperly balanced tires can also slowly strain the wheel bearings and suspension system. Considering that every time you hit a bump, the tires get a bit more out of balance, experts recommend re-balancing every four to six thousand miles. Of course, whenever you change tires, they should be balanced at the same time.
  • Rotation: Rotating the tires can extend their useful life, improve gas mileage and again give you a smoother, more even ride.

Tire Rotation Examples For maximum mileage, rotate your tires every 5,000 miles.

tire-rotation

Tires Past Their Prime

You may not have given this any thought, but tires – even ones never used – do have a shelf life.

How is this possible? Through the processes of oxidation and devulcanization.

While the materials in our tires are mostly inert, some of it still reacts with the atmosphere.

Molecular cross-linking makes the rubber more rigid and less pliable. It may take years, but non-the-less it happens. In fact, oxidation and devulcanization can account for 30% of the Styrene-butadiene rubber found in our modern day tires being lost over time.

As a rule of thumb, any tire over six years old should not be on your vehicle. Over ten years, and they should be considered definitely hazardous to drive on.

Tire Warranties: Most tire warranties extend for four years from the date of purchase or five years from the week the tires were manufactured. So if your tire is two years old when you purchased it, the warranty will extend past the five year manufacture date. This of course assumes you have kept the receipt!

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 A Crash Course in Tireology:

Reading & Understanding Your Tire’s TIN Code

Here’s a dirty little secret some auto dealers aren’t telling you – there’s no law against selling you older tires!

So how do you know how new your tire really is? It’s not like they come with a birthday… or do they?

The manufacture date of every tire is stamped in code on the sidewall in what’s called a Tire Identification Number (TIN) mandated by the DOT – Department of Transportation.

Know how to read the code, and you can tell precisely how old those “new” tires actually are.

Here’s how it works…

U.S. DOT Tire Identification Number – How Old Is That Tire? Right above the rim you’ll see a series of small numbers and letters, beginning with “DOT” – for Department of Transportation – indicating the tire meets all federal standards.

The numbers of most interest will be the last four telling you when the tire was made. The first two signify the week, the last two the year. For example, the numbers 2512 means the 25th week of 2012.

DOT U2RR LVLS 2512
25 Manufactured during the 25th week
12 Manufactured in 2012

NOTE: If you only see a three digit number like 258, then forget about buying the tire. It was manufactured before the year 2000.

There are other numbers which are marketing codes used to contact consumers if a tire defect requires a recall. We’ll discuss this further down on the article.

Tire Fundamentals

Federal law requires tire manufacturers to place standardized information on the sidewall of all tires. This information identifies and describes the fundamental characteristics of the tire and also provides a tire identification number for safety standard certification and in case of a recall.

Information on Passenger Vehicle Tires

tire-radial-image

— P —

The “P” indicates the tire is for passenger vehicles.

The three-digit number following it gives the width in millimeters of the tire from sidewall edge to sidewall edge.

The next two-digit number after the backslash is the aspect ratio, giving the tire’s ratio of height to width. Numbers of 70 or lower indicate a short sidewall for improved steering response and better overall handling on dry pavement.

— R —

The “R” stands for radial. Radial ply construction of tires has been the industry standard for the past 20 years. The two-digit number after it is the wheel or rim diameter in inches. If you change your wheel size, you will have to purchase new tires to match the new wheel diameter.

Tire Load Index

Moving past the “R” designation, we get to the next set of numbers, known as the Tire Load Index. These two or three-digit numbers measure how much weight each tire can support. Note: You may not find this information on all tires because it is not required by law. However, it IS important to know, as overloading your vehicle can put too much strain on the tires which can result in failure and blowouts.

If it isn’t on your tire, ask before you buy! If your dealer doesn’t know, go elsewhere. — M+S –The “M+S” or “M/S” indicates the tire has some mud and snow capability. Most radial tires have these markings.

Speed Rating You may also see a letter indicating a “speed rating” indicating the speed at which a tire is designed to be driven for extended periods of time. The ratings range from 99 miles per hour to 186 mph. Not all tires have this as this rating is not required by law.

Here are the Letter Ratings and their corresponding Speeds.

Letter Rating Speed Rating
Q 99 mph
R 106 mph
S 112 mph
T 118 mph
U 124 mph
H 130 mph
V 149 mph
W 168* mph
Y 186* mph

*For tires with a maximum speed capability over 149 mph, tire manufacturers sometimes use the letters ZR. For those with a maximum speed capability over 186 mph, tire manufacturers always use the letters ZR. (But in all frankness – where can you go in the USA at 186 mph? Even more – who can afford the type of performance vehicle capable of those speeds in the first place?)

Other DOT Numbers You Should Find Useful

We already discussed how to find out when your tire was manufactured. Here are some other facts you’ll learn from the DOT codes.

Tire Ply Composition and Materials Used: The number of plies indicates the number of layers of rubber-coated fabric in the tire. In general, the greater the number of plies, the more weight a tire can support. Tire manufacturers also must indicate the materials used in the tire, which can include steel, nylon, polyester and so on.

Maximum Load Rating: This number is the maximum load in kilograms and pounds that can be safely carried by the tire.

Maximum Permissible Inflation Pressure: This number is the greatest amount of air pressure that should ever be put in the tire under normal driving conditions.

UTQGS Information

The “Uniform Tire Quality Grading Standards” or UTQGS is yet another set of designations you’ll typically find on your tires.

Treadwear Number: This number indicates the tire’s wear rate. The higher the treadwear number, the longer it should take for the tread to wear down. For example, a tire graded 400 should last twice as long as a tire graded 200.

Traction Letter: This letter indicates a tire’s ability to stop on wet pavement. A higher graded tire should allow you to stop your car on wet roads in a shorter distance than a tire with a lower grade. Traction is graded from highest to lowest as: “AA”,”A”, “B”, and “C”.

Temperature Letter: This letter indicates a tire’s resistance to heat while properly inflated and not overloaded. Excessive speed, under-inflation or excessive loading, either separately or in combination, can cause heat build-up and possible tire failure.

From highest to lowest, a tire’s resistance to heat is graded as “A”, “B”, or “C”.

After reading all this, we’ll bet you’ll never look at your tires in the same mundane way again!

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Defective Tires & Recalls

You can do your tire-hunting homework. You can inspect your tires at regular intervals. You can make sure you avoid potholes and hitting curbs, that your tires are always properly inflated and the wheels are rotated and balanced.

But you can’t divine whether there is a hidden manufacturing defect just waiting to ruin your day, or even end your life.

Defects happen. No matter how stringent the manufacturing process, nothing is ever 100% accurate. But here’s the thing – you probably won’t learn of your tire’s defect until someone else has experienced a problem or an accident because of it.

Even then, you may not be notified until months (or even years) after the incidents have happened. Then again, you may never be notified at all if you or the dealer didn’t send in your tire registration information. Or you may have moved. Or the information may have simply been lost. You get the picture. When push comes to shove, you are ultimately responsible for making sure you stay alive and well.

Rely solely upon the government or the corporations, and you’ll be playing a dangerous game of Russian Roulette. Think this is an exaggeration?

According to the National Transportation Safety Board, only about one out of five recalled tires are actually returned to the manufacturer. In fact, it is entirely possible a “recalled” tire can still end up being sold at some retail stores.

This is exactly what happened on a February day in 2014 to a church van involved in a deadly Florida accident. NTSB investigator Don Karol stated: “The van suffered a left rear tire tread separation and then went off to the right, off the road and rolled over.”

Here’s the sad part. The mechanics at the New Port Richey Sam’s Club who installed the tires didn’t realize that particular tire model had been recalled a year earlier. The church officials who purchased the tires never suspected the tires they bought were unsafe.

The end result? Two lives lost and eight people injured due to a preventable accident.

Not convinced? Then look at this:

Two Texas youths were killed while driving back to Sul Ross State University in August 2011. Once again, the tread came off a tire, causing the pickup they were in to skid and overturn. And once again, problems with the particular tires involved were first identified 15 months before the accident that took these young men’s lives. 41,000 Wrangler Silent Armor tires produced in 2009 tires were then recalled as a result of this tragedy.

As you see, it can take months before a defect becomes severe enough to cause problems. The tires on the church van mentioned above were on the vehicle 18 months before the tread separated from the tire and wrapped around the axil – causing the van to overturn.

With the Goodyear tires, it took over a month between when the official recall announcement was made and all the notices were sent out to affected consumers.

However, the prize must go to Firestone – in 2000 they were forced to recall 6.5 million tires after a series of 46 deaths happened due to, once again, tread separation. This was a year after Firestone had already recalled 46,000 tires of the same type being used overseas.

However, the real tragedy was that Firestone at first downplayed any connection between the tires and the accidents – putting off a recall in the USA, and placing thousands of unwary drivers at risk.

Information Isn’t In a Single Government Database

You would think that the United States government would have a single database listing all the tire recalls, along with the appropriate production numbers to check them by. You would think wrong. You have to go to multiple sources to find out if your tire is one of those affected by a recall.

However, there is a private database put out by the Tire Safety Group (http://www.tiresafetygroup.com) where you can check to see if your tires are either expired or under recall.

It will be a few minutes of your time well worth the effort to check out.

Considering that tire failures are responsible for up to 600 deaths per year, and thousands of other road mishaps – making sure your tires are in tip-top shape is not only a good idea, it’s a “no-brainer” as well.

Don’t Be a Statistic!

While 600 deaths may not sound like much statistically speaking – if one of those deaths happen to you, your spouse or your child, they cease being a statistic and start being a very real living nightmare and human tragedy.

Drive safe!