Tuesday, February 7, 2012

The danger of older car tires

For the past couple of days we've discussed various issues surrounding car tires, first here and then here. Today something else came to my attention - a danger of which I'd not previously been aware.

It seems that tires can be safely stored and used for several years after their date of manufacture. However, after that 'safe period', the rubber and other materials used in their construction can deteriorate, leading to unsafe conditions such as tread separation, etc. In 2008, ABC News reported:

Despite years of study that point to a mounting toll of deaths and injuries attributed to aged tires, the National Highway Traffic Safety Administration (NHTSA) has refused to issue a warning to consumers on the issue.

"We are extraordinarily disappointed by the fact that they are saying, 'We know this is a safety problem,' but they won't tell consumers," said auto safety expert Sean Kane.

As tires age, they can dry out and become brittle, leading to potential catastrophic tire tread separations. Kane's private research firm Safety Research & Strategies has so far tracked 167 vehicle crashes it attributes to aged tires, with 192 injuries and 139 fatalities. "An old tire is like a ticking time bomb in many ways," said Kane. "You don't know what's going on inside it. That's what makes it so dangerous."

NHTSA has known about the risks of aged tires for years, and in a 2007 report to Congress the agency acknowledged that "tire aging is a serious safety issue." NHTSA's report noted that insurance statistics from a number of states showed 84 percent of tire-related claims were for "tires over 6 years old." NHTSA refused a request, however, from Ford Motor Co. to impose a six-year shelf life on tires, based on the company's independent research.

"We have rejected that notion," said NHTSA spokesperson Ray Tyson, pointing to the fact that some tire and auto manufacturers have issued their own shelf life recommendations for tires, which he said is "sufficient." Bridgestone/Firestone, Michelin and other tire manufacturers have issued bulletins recommending a 10-year shelf life for tires. Auto companies, such as Ford, Chrysler and Toyota, have issued 6-year recommendations.

There's more at the link.

Intrigued, I asked my contact at a local dealer about this. To my surprise, he was hesitant to answer, at least in the hearing of other managers. Eventually we managed to get a moment of privacy, and he informed me that age does, indeed, appear to be a factor in tire safety: but tire wholesalers and retailers typically don't want to acknowledge it, because they have older tires in stock, and they wouldn't be able to sell them if the problem were more widely known. As it is, they can and do sell them, and if some of them exhibit problems they'll replace them under warranty. That's cheaper than trashing all of them, because some older tires (particularly those fitted to vehicles that don't drive very often, or very far, or very fast) might not give any trouble.

I was pretty upset to hear that tire suppliers may be risking the lives of their customers in this way, and asked him how one could identify the age of a tire. He pointed me to a very useful British Web site, Carbibles.com, which includes a section labeled 'Wheel & Tyre Bible' (yes, Britain spells 'tire' with a 'y' instead of an 'i'). This is packed with information about any and all aspects of tires and their use. Here's what it says about tire dates.

DOT Codes and the 6-year shelf life

As part of the DOT code (G in the tyre marking above), there is a tyre manufacture date stamped on the sidewall. Oddly this code is sometimes only one one sidewall so you might need to get under your car and look at the inward-facing side of the tyre. Take a look at yours - there will be a three- or four-digit code. This code denotes when the tyre was manufactured, and as a rule-of-thumb, you should never use tyres more than 6 years old. The rubber in tyres degrades over time, irrespective of whether the tyre is being used or not. When you get a tyre change, if you can, see if the tyre place will allow you to inspect the new tyres first. It's not uncommon for these shops to have stuff in stock which is more than 6 years old. The tyre might look brand new, but it will delaminate or have some other failure within weeks of being put on a vehicle.

Reading the code. The code is pretty simple. The three-digit code was used for tyres manufactured before 2000. So for example 1 7 6 means it was manufactured in the 17th week of 6th year of the decade. In this case it means 1986. For tyres manufactured in the 90's, the same code holds true but there is a little triangle after the DOT code. So for this example, a tyre manufactured in the 17th week of 1996 would have the code 176∆ .

After 2000, the code was switched to a 4-digit code. Same rules apply, so for example 3 0 0 3 means the tyre was manufactured in the 30th week of 2003.

If the tyre has a 3-digit code, do not buy it. It will be too old.

There's much more at the link. I really think that entire Web page is essential reading, for safety reasons; so please take the time to click over there and learn more about the subject. Some of its information may not apply to the USA or the country in which you're reading it, but you can use that information as a starting point to find out where your national markings and/or regulations differ. (For US readers, see this page at the Tire Rack Web site for further information about US age codes.)

Anyway, there's something else to think about when checking your existing tires, or planning to purchase new ones - and it's certainly a strong argument against buying older used tires!



Erik said...

This is an even bigger problem if you use tires made for cold weather and icy conditions. An old tire wont adapt as well to the temperature, and wont get the same grip, making it useless for driving in winter conditions.

It's a fairly wellknown issue in Scandinavia, I've known about it for years and I've seen it in different shows and read it in articles. I think most tire dealers wont sell older tires, they get new ones every year. I imagine this is a price issue, since people that want it can find cheaper tires at small shops, so I guess the small shops sell older tires. (Never bothered to look myself)

Some people will do anything to get a bargain, before it became law that you were required to have appropriate tires in winter conditions there were lots of people using the "summer" tires all year around. They figured they were safe since they had never had an accident before...

The way I heard it as a reason that the old tires are still sold is that most people only drive short distances, to and from work and the store on well maintained roads in moderate speeds. If so they really dont benefit much from better tires, the old stuff will still hold up well enough for them.
As long as there's no situation where they need the tires to brake or steer away from an accident...

Anonymous said...

From 15th to 17th C. the word was spelt tire and tyre indifferently. Before 1700 tyre became generally obsolete, and tire remained the regular form as it still does in America. In Great Britain tyre was revived to describe the rubber rim of bycycles and cars etc. Just to be awkward it is also sometimes used for the steel tires/tyres of locomotive wheels

The British evidently resurrected the archaic spelling - tyre - to distinguish between the modern pneumatic tire, made of rubber, and its iron predecessor used on wagon wheels.


Carteach said...

Some of the tire aging process involves 'Off Gassing' of the petroleum products used in tire manufacture. One method of slowing that aging process is to 'Bag' the tires. Typically a well sealed trash bag is sufficient. This is the reason many high end sport tires come heavily wrapped in plastic when new.

Avoid 'tire dressing' and Armourall like the plague, if you want tires to last a long time without checking. They are counter productive if long life is the goal. On the other hand, a good coat of old fashioned paste wax doesn't hurt, and may help.

Were I to store a set of rims and tires for future use (and I do), they would be aired up, clean, and bagged.

Old NFO said...

Good point Peter, I treat my tires like I do all the hoses in the engine compartment; 4 years and new ones go in (or on)...

Anonymous said...

Had one tire on my old truck for 26 years. Wheel was dented & a new tire would not have seated & sealed, but the old one was well-adapted. Didn't drive fast or far generally. Glad I got lucky.

Anonymous said...

Heck, When I first started driving tires had inner tubes and 2-inch white walls.


Anonymous said...

My tire dealer went to great lengths to inform me of this. I had a 20 year old spare on my jeep. Never needed to use it. I am a high milage driver and seldom put less than 18K miles/year on my car. So at most they get replaced every 3 years.

The Raving Prophet said...

I tend to be VERY picky about my tires. It's kind of a rare thing for me to buy a model of tire that's been on the market for that long, let alone risking getting a too-old tire.

Much of this is the problem of people who just go to the tire shop and ask for the cheapest stuff they have. If you're like me and you don't like buying anything but the top of the line (note: best in tires is rarely the most expensive), it's much less an issue. The nicer tires tend to not be made in China but in the US or Europe, and when the tire model was introduced two years ago, they can't possibly be too old.

Anonymous said...

I ran into this problem up close and personal when my right rear tread separated in a turn. It did leave a nice donut on the side of the road. Taking the remains back to the tire shop I learned that Michelin tires went out of warranty when they were 5 years old. My tires were 7...

I did learn to read the age code on tires after that.