Tires really do have an expiration date

TOM: What’s the reasoning? Well, the Goodyear pension plan is seriously underfunded.

RAY: Actually, it’s about the deterioration of the rubber, Eric. If you take a rubber band and toss it in your kitchen drawer, when you go to stretch it a year later, what happens? It’s all dried out, and it breaks.

TOM: There’s a similar, though much slower, process happening with your tires. Over time, the ozone in the air degrades rubber. Just from being in Earth’s atmosphere, tires dry out, crack and, eventually, fail to hold air.

RAY: So how’d they come up with the six-year time frame? Well, it’s somewhat arbitrary. They looked at a number of factors: the rate at which rubber decays, how the average person cares for his or her tires, the real-life data on tire failure and the tire sales numbers for Q4. They put it all together, and they came up with a guess of six years.

TOM: So, it’s a guess. Your tires may last longer or may fail sooner. But it’s a reasonable guess that errs on the side of safety. And in reality, most tires have their tread used up in less than six years anyway. So it’s only an issue for people who don’t drive much, and for spare tires that don’t get rotated into the mix.

RAY: You may have a little more leeway with your spare, since you’re not actually driving on it every day. But in an emergency, if you were forced to use it, you’d have to drive slowly and carefully, and then replace it as soon as possible. If it were me, I’d replace a spare that’s 10 years old.

TOM: And speaking of replacement tires, you now have one more thing to think about at the tire store. Like bread and milk, you now have to make sure your tires are “fresh.”

RAY: Right. If tire manufacturers are telling us that tires have a six-year shelf life, regardless of use, then you don’t want to buy tires that have already wasted a year of their useful life stacked up in a retailer’s showroom or an overheated storage trailer.

TOM: How do you know when your tires were made? It’s on the tire. One of the numbers printed on the sidewall is a four-digit number, like 1711. That means the tire was made in the 17th week of 2011. Now, wouldn’t it be easier if they took a lesson from milk and printed an “expiration date”?

Dad shouldn’t pick this nit

Dear Tom and Ray: I need your opinion on whether something the driving instructor is teaching our daughter to do is hard on the car. When parallel parking, he has her turning the wheels in place while the car is stopped in order to position it for the next move. We were practicing today, and echoes of my dad were going through my head — that doing this is hard on the steering components, and that you should try to be moving slowly when you turn the wheel. Now, I’m not going to make her challenge her instructor on this, but I do want to know if this is bad for the car. If not, I’ll shut up and leave it be. But if it is as I remember, then I want to provide her with some balanced information on this. I know sometimes it’s unavoidable, but is my memory just crap, or is there something to this?— Jeff

TOM: Well, we don’t know about your memory, Jeff. Do you remember writing to us last week with this same exact question?

RAY: Actually, your dad was correct. It does place more strain on the steering components and tires when you steer the front wheels while the car is stopped.

TOM: But it’s hardly worth worrying about. Think about the amount of time you spend parallel parking versus the amount of time you spend actually driving. It’s minuscule. So, even though it’s a little harder on a few of the car’s parts, its overall effect on the life of the power-steering pump, or your tie-rod ends, or your front tires, is insignificant.

RAY: And the long-term cost is tiny compared with the increase in insurance rates you’ll pay when she creases the Mercedes in front of her while parallel parking because she’s worried about the wear and tear on Daddy’s power-steering pump.

TOM: Right. She’s got more than enough to think about now in learning to drive and learning to parallel park. The last thing you want to do is add another thing for her to think about, especially if it’s not important.

RAY: Once she’s been driving for a while and can parallel park the car in fewer than 24 attempts, then you can suggest that she start moving backward slowly as she turns the wheel. But it should be low on the priority list, Jeff.

Send your comments or questions for Tom and Ray to: Car Talk Plaza, P.O. Box 3500 Harvard Square, Cambridge, MA 02238. Listen to them Saturdays at 10 a.m. on 91.3 FM or 88.5 FM. Visit them on the Internet at www.cartalk.com.

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