BATMAN

Should tires be assigned a shelf life, like groceries, milk or eggs? A safety research group says aging tires develop cracks or weaken when they sit around unused.

TIRE MAKERS in Britain have just issued a warning to consumers. Replace tires that are more than ten years old, even if the tread’s not worn. And for a tire that hasn’t been used, like a spare, replace it after six years.
Reviewing U.S. lawsuits, the research group says that many accidents involved old tires. According to strategic safety expert Sean Kane, “we’ve been able to document in a very short period of time at least 20 cases involving serious injuries and fatalities in the United States, and we’ve only scratched the surface of this issue here.”
The tire that blew on Bill Cartus’ antique car wasn’t worn at all, but it was 11-years old. “Somehow we hit something and the last thing I remember is that we were spinning through the air two or three times. I think there were some other eyewitnesses that could tell how many, and the next thing I remember is waking up in the car and the top was gone,” Cartus said. “No one has ever told me, well, you shouldn’t drive on those because they are old. They look great.”
Width & aspect ratio
The "P" in front of the number stands for "passenger."* "215" represents the width of the tire in millimeters. "65" is the ratio of height to width. The "R" stands for "radial" and the "15" is the diameter of the wheel in inches. A "B" in place of the "R" means the tire is belted bias construction. A "D" in place of the "R" means diagonal bias construction.

*This tire example is based on the P-metric sizing system, a scale introduced in 1976 for compact cars. An older tire measuring system, the alpha-numeric, uses letters A through N to identify tire size and load carrying capacities.

Service Description:
"89H" in this example, consists of the load index (89) and speed symbol (H). This only appears on speed-rated tires.

DOT code:
The letters "DOT" certify compliance with all applicable safety standards established by the Department of Transportation (DOT). Adjacent to this is a tire identification or serial number. This serial number is a code with up to 11 digits that are a combination of numbers and letters.

Ply composition:
The sidewall also shows the type of cord and number of plies in the sidewall and under the tread. The DOT requires tire manufacturers to grade passenger car tires based on three performance factors: treadwear, traction and temperature resistance.

Load limit:
The maximum load is shown in lbs. (pounds) and in kg (kilograms), and maximum pressure in psi (pounds per square inch) and in kPa (kilopascals). Kilograms and kilopascals are metric units of measurement.

Treadwear, traction & temp.:
The treadwear grade is a comparative rating based on the wear rate of the tire when tested under controlled conditions on a specified government test track. A tire graded 200 would wear twice as long on the government test course under specified test conditions as one graded 100. Traction grades, from highest to lowest, are A, B and C. They represent the tire's ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete. The temperature grades, from highest to lowest, are A, B and C. These represent the tire's resistance to the generation of heat when tested under controlled conditions on a specified indoor laboratory test wheel.

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But the U.S. tire industry says a shelf life is not the answer. Donald Shea of the Rubber Manufacturers Association said: “What it is is a complex series of events that can make a tire deteriorate. One, is the amount of mileage; two is the abuse it takes on the road; third and perhaps most important is the maintenance that is given or not given to the tire. If the public gets the impression that they could continue to use a tire until that use by date that could send clearly the wrong message.”
When the NHTSA proposed an upgrade to new tire standards it also proposed an aging standard. That was deferred for two years because no one could agree on a reliable test that could artificially age a tire. The NHTSA is in the process of determining which test is best and hope to have research done by next summer.
For now, to find a tire’s age, check its DOT code — but that’s not easy. At the very end are three numbers, for instance “414,” meaning the tire was made the 41st week of the year 1994.
To find a tire’s age, check its long DOT code, found on the side of the tire. At the very end are three numbers which indicate the week and year the tire was made, for example a DOT number ending with 414 means the tire was made the 41st week of the year 1994. Complicated!
But Bill Cartus, for one, says he’ll be checking now: “I buy milk; I look for the latest date. When I go buy eggs, I look for the latest date. On my next set of tires, I am going to be looking for that date.”
But some believe that, like groceries, tire dates ought to be a lot easier to find.

Little Goat

That is why Michelin won't sell passenger tires that are over three years old, to the U.S. at least. BTW, the DOT week is only on one side of the tire