When consumers think of tires, if they think of them at all, they likely think about proper tire inflation. As important as proper inflation is--underinflated tires increase rolling resistance and decrease fuel economy, while both overinflated and underinflated tires cause uneven tire wear--it is not the only thing consumers need to think of when it comes to the rubber that's touching the road.
Tire Life
The average life of a set of tires varies based on driving conditions, driving style, brand, tire composition, and proper maintenance, but the average life span is probably 40,000-50,000 miles for most sets. A shorter life span may be the norm for tires on sports cars, because they may use a softer composition that allows for better handling but causes the rubber to wear faster.
Tire wear isn't the only thing that defines a tires life span. Even tires that haven't worn out yet may need to be replaced, due to a condition called "dry rot." Dry rot occurs as sunlight causes the rubber on the sidewalls to crack over time. If dry rot has gotten bad enough, the tire will need to be replaced.
Sidewalls can also experience "air bubbles," usually after the tire has hit something, such as a curb. When this occurs, the tire usually needs to be replaced.
Tire Types
There are a few basic tire types: All-season, snow, and summer tires are the main ones. All-season tires are designed to provide the best traction in various weather conditions, while snow tires are meant to be at their best in the fluffy white stuff. Summer tires are meant for ideal weather conditions, and those who own cars with summer tires and live in climates where snowfall is a common occurrence usually swap them for snow tires or all-seasons every six months.
When choosing a tire type, it's best to consider what tires were on the car originally, and what kind of climate you live in.
Tire Sizes
Tire sizes are listed in a format that looks like this: P225/60R15 92S. The "P" indicates that tire is intended for a passenger vehicle. The "225" is the width, in millimeters, of the tire. The "60" is the tire's aspect ratio, also known as profile. This is the percentage of the sidewall compared to the width of the tire. For example, the "60" means that the sidewall's height on this tire is 60 percent of the width of the tire.
The "R" means that the tire is a radial tire as opposed to bias-ply construction--almost all tires sold today are radial. The "15" is the wheel diameter, in inches. The "92S" is the service description--the "92" is a number representing the load index of the tires, or how much weight the tires can carry. The higher the number, the more weight the tires can support.
Finally, the "S" stands for the tire's speed rating. There are several speed ratings, each designated by a different letter. The speed rating signifies how fast the car can travel before the tire is in danger of failure.
Tire Maintenance
Other than keeping the tires properly inflated, the most important tire maintenance that can be performed is a tire rotation. Tire rotations allow the tires to wear evenly, so that instead of replacing tires piecemeal, owners can replace all four tires as a set. Tire rotations also allow the tires to last longer.
TIre wear is measured by tread depth, either in millimeters or 32nds of an inch. Most dealers and service shops would likely recommend replacement at 4/32nds of an inch--by comparison, new tires would have tread depths of 12/32nds of an inch.
Keeping Tires Rolling
The importance of tire maintenance cannot be overstated, since tires are what keep the car on the road. With proper care, owners should be able to get the maximum mileage out of their tires.
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