1991 Acura NSX Long Term Road Test

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1991 Acura NSX: Ancient Tires

November 22, 2011

NSX DOT Code.jpg

I recently wrote an article on aging tires that opened my eyes to an often-overlooked aspect of car maintenance. For years, many of us (myself included) have looked at tread wear as an indicator of when to replace a tire. But the age of the tire itself is just as important. Old tires develop cracks over time, which can potentially lead to tread wear separation.

When you buy any used car, especially a low-mileage vehicle like our 1991 Acura NSX, you should make it a habit to check the Department of Transportation (DOT) identification number on the tire. I was curious about the tire vintage on long-term cars we bought used, so I went to check them out.

Our NSX illustrates one of the difficulties you may encounter when you're trying to determine the age of a tire. The lettering on two of the four tires was facing the inside of the vehicle. This car sits very low to the ground, so the only way for me to see the DOT code would be to jack up the car and peek underneath. Thankfully, the code was visible on the other two tires.

The code on the front right tire reads "1502." This means it was manufactured in the 15th week of 2002. The code on the right rear tire says "0302," or the third week of 2002. The tires on the left side of the car face inward, but I'm going to assume they are of a similar vintage. This means that they are very close to 10 years old.

Consumers get mixed messages on when they should replace their tires. Many automakers recommend six years, regardless of tread. Most tire manufacturers say you should get annual inspections after the six-year mark, but that 10 years is the maximum service life.

We have Bridgestone tires on the NSX. If you look at the tires, the tread looks like it's in good condition, but the company says its tires have a maximum service life of 10 years. Our NSX is right on the edge. There are a couple other factors that could tire roadworthiness over the edge.

Tires wear out faster in warm-weather states. And it certainly doesn't help matters much when anyone who drives the car really steps on it to see what it can do.

So we're going to have to get a new set of tires as soon as possible. Similarly, our other used car, the 1985 Porsche 911, is going to need new rubber. In addition to the shallow tread, the tires are pretty old too. Here are the DOT codes for the 911: front right 4002, rear right 0105, left rear, 5204. The front left tire was mounted inwards, but if three out of four tires need replacing, we may as well get a full set.

For those of you who haven’t bought a new set of tires in a while, take a look at the DOT code and let us know how old your tires are.

Ron Montoya, Consumer Advice Associate

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