Tue09022014

On The Road

When the rubber hits the road: Signs that it’s time to buy new tires

Q: I have been told that I need new tires, but it looks to me as if they still have plenty of tread on them. When I mentioned that, I was told the tires are old and are forming cracks in the rubber. When do tires become “old,” and do they really need to be replaced before the tread is worn down?

A: Yes. As auto tires (or any rubber products) age, the rubber deteriorates and eventually develops cracks. If a tire has severe cracks in the rubber compound, it must be replaced as soon as possible. Visible cracking in the tire increases the likelihood of tire failure, regardless of the condition of the tread, so you have been given good advice to purchase new tires.

Here are a few things to keep in mind:

• Know the correct tire size and rating that your vehicle manufacturer has designed your vehicle suspension to be compatible with.

• Note that the tire rating involves a speed rating. A high-performance vehicle will demand a higher-speed-rated tire. This rating is important.

• If you have an all-wheel-drive vehicle, the general rule is to install four new tires at the same time. Installing only one new tire could cause damage to the drivetrain and have a negative effect on the operation of the antilock brake system.

When do tires become ‘old’?

In general, the life of a tire is eight to 10 years. But this depends on the environment the tire operates in. For example, a climate such as an Arizona summer with 110 F heat is extremely hard on tires. So is not having the correct air-pressure level in your tires. Too little air pressure causes the tires to become much hotter when driven at freeway speeds. This extra heat leads to faster tire degradation, and can cause even a good tire to fail. Overinflation is also bad and can result in your tires not being able to stop within a safe distance or failing due to exceeding the tire design pressure.

A “new” tire can be six to 12 months old before it is installed. So, how do you know what you got or what you are getting? As of the year 2000, there is a four-number birthdate molded into the sidewall of the tire. This date represents the week of the year and the year the tire was made.

Barring the deciphering of the birthdate, where can you feel confident about buying new tires? Here are some tips:

• Do not buy tires from any business or person that has them sitting out in the sun. The sun’s ultraviolet light deteriorates the rubber.

• Do buy tires from a business that sells a lot of tires and stores them inside out of direct sunlight. This way, you can be more confident that the tires have not been sitting on the shelf for years, such as might be the case at a gas station or a discount store. An independent repair shop or an auto dealer that orders tires as needed from large, wholesale warehouses is a good choice.

• The quality of the tire matters. Purchase brand-name tires (Michelin, Bridgestone, Pirelli, etc.), making sure that they are the correct size and grading/rating.

At each vehicle service, your tire tread depth, tire pressures, evenness of tire tread wear and condition of the rubber should be checked.

The most important thing to remember is that it is extremely unsafe to drive with either underinflated, overinflated and/or cracked tires. Check them regularly and replace them as soon as possible when needed.

Warren McCord is an ASE Certified Master Technician and owner of Dean’s Automotive Inc., 2037 Old Middlefield Way, Mountain View. For more information on the shop, call 961-0302 or email McCord at This email address is being protected from spambots. You need JavaScript enabled to view it. .

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