Be mindful of tire class and size — your car’s performance depends on it

Too many drivers don’t think about their tires until they have to swerve or brake suddenly, or they have a flat — often with serious consequences. About 9 percent of vehicle crashes are tire-related, according to estimates from a National Highway Traffic Safety Administration study.

But many could be prevented just with proper tire maintenance, so it’s important to inspect your tires every month for wear.

To gauge tread depth, all you need is a quarter. Put George Washington’s head into one of the big grooves. If the top of his head is flush with the tread, you have about one-eighth-inch of tread left, meaning you have some grip remaining for rainy or snowy conditions.

That’s the time when you should start shopping for new tires. If you can see space above Washington’s head, you may need to replace your tires immediately.

Be an informed buyer

Before you start shopping, it’s worth knowing these tire basics:

• Tires carry a speed rating, usually from S (112 mph) to Y (186 mph), with some winter tires having a lower speed rating. That indicates the tire’s maximum speed when carrying a load. Higher speed-rated tires tend to have better grip and handling but wear out sooner, generally making them more expensive.

• Tires come in a variety of sizes, so it’s important that you get the right one for your car. On the side of each tire are numbers like this: 215/ 60R16. The 215 refers to the width of the tread in millimeters; 60 is the ratio of sidewall height to tire width; and 16 is the size of the wheel in inches. Most cars also list this on the driver’s doorjamb.

• Online retailers usually offer some of the lowest prices, but you may have to pay for shipping the tires to you, plus installation and balancing costs.

Local car dealers and tire retailers may match those prices or give you a deal on installation. Keep an eye out for promotions, including manufacturer rebates and sales.

• Prices vary by size as much as by brand and model.

Tire value: type matters

Each tire type has strengths and limitations.

• All-season tires are made to perform well in a wide range of conditions and achieve a long tread life.

• Performance all-season tires tend to grip better and provide better handling — but sometimes at the expense of longevity.

•UHPall-seasonandUHP summertiresdelivertheultimate an even shorter tread life.

The general rule is that higher-performance tires cost more and wear faster, leading to a greater cost per mile.

It’s usually best to stick with the type of tire that came on your car when you bought it. Downgrading to another tire type to save money could hurt your car’s braking and performance.