When to Get New Tires

By Matt Keegan
Last Updated 06/15/2015

Purchase a car and you should get several years out of the tires. Generally, you can maximize the life of your tires by rotating them twice a year and getting the occasional front end alignment. But tread wear, age and road damage will also take its toll on your tires, necessitating the purchase of replacements. Here's what you need to know about tires and when to get new ones.

The Basics

Your tires are the only thing that separates your car from the road. It is important that your tires be properly inflated and in good condition.

Car manufacturers work conjointly with tire makers to ensure that the right tires are made for each new model. That doesn't mean different tires cannot be used, but all four tires should match. Matched tires provide more even wear and optimum handling.

Warning Signs

Most tire problems are apparent through careful observation. If you notice cracks or cuts on the sidewalls, or bulges and blisters, you need to replace your tires. The latter problem is particularly dangerous as it points to weak spots that could lead to sudden tire failure.

Another warning sign has to do with tread wear. Today's tires come with tread wear indicator bars that run across the tread. When the bars are exposed, that means you only have one-sixteenth of an inch of tread left, which is the absolute minimum for safe driving.

Even if the tread bars are not showing (or are not present because the manufacturer didn't install them) uneven tread wear might also be found. This problem occurs if the tires are damaged, the wheels are misaligned or certain suspension parts are worn. Improperly inflated tires — those that are overinflated or underinflated — are subject to wear too.

Physical Inspection

A visual inspection of the tire may not always reveal a problem. If you feel a vibration or experience thumping while driving, and it feels like it is coming from underneath the car, then your tires may be out of balance. Vibration in the steering wheel while driving indicates that your suspension system has problems. Take your car in for a mechanic's inspection.

You can also confirm tread wear by conducting the Lincoln penny test. Here, you would stick Abe's head into the tread. If any part of his head is visible, then your tires should be replaced.

Shopping for Tires

You have a number of places to shop when it comes time to buy new tires. Your car dealer, a favorite garage, tire retailers, major chain stores and some warehouse clubs sell new tires. Pricing information can usually be found online, making it easy for you to comparison shop.

When buying new, you have multiple tire choices available to you. But if you are happy with the tires that came with your vehicle when it was new, then stay with them. Those are the same tires ordered by the car manufacturer from the tire company.

For some consumers, the original equipment manufacturer tires will cost them more money than they planned on spending. Fortunately, there are other tires that are sufficient for your car. But keep this point in mind: different tread patterns can affect handling — you don't want to buy tires that you don't like and will be stuck with for the next several years.

Reading Your Tires

Retail shops typically have access to computer databases that can provide the right size tire for your car. At the same time, it is a good idea to acquaint yourself with the information printed on your tire's sidewalls.

For example, your tire may say: P225/55R17 95H. The "P" represents passenger tire, the first three numbers are the width of the tire, which is measured from sidewall to sidewall in millimeters.

After the backslash the next two numbers represent the ratio of height to width or what is also known as the aspect ratio. This is represented by the "55" in the tire size above, and indicates that the sidewall's height is equivalent to 55 percent of the tire's width. The "R" stands for radial and the two numbers following represent the diameter of your wheel. Following that is the load index and the speed symbol for the highest safe speed at which these tires can operate.

Tires may also have additional information such as M+S, representing mud, and snow and the name of the manufacturer.

Additional information may also be present, usually a reference symbol such as DOT, which explains that the tire is compliant with the U.S. Department of Transportation tire safety standards. That information typically precedes the main codes for the tire. Following the compliance code is a two-letter code identifying the plant that manufactured the tire. The tire size code number and tire type code will also be listed.

Of notable importance is a four-digit code that completes the sequence. It represents the date of manufacture or what some call the "born on" date for the tires. For instance, tires listed as 4814 were manufactured during the 48th week of 2014 or early December. Keep this number in mind when buying new tires — a newer date is better as tires age even when not fitted to a car.

Buy Two or Four

Buy tires in groups of two or four when you replace them. Replacing one or three tires will result in uneven wear. If you choose two tires always place those on the rear of the vehicle.