How long before you need to replace tires?

Before you start shopping, it’s good to know some 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 cross section width, the widest distance from one sidewall to the other when mounted on the wheel; 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, too, including manufacturer rebates and sales.

Last, note that price varies by size as much as by brand and model. Expect to pay more for larger tires.

Little compares to the exhilaration of taking to the open road, ready to embark on a road trip or new adventure. But before you put the pedal to the metal, it’s important to make sure your car’s maintenance is up to date. At the top of the list: ensuring that your tires are road ready. Here are five telltale signs it’s time to replace your tires.

Why tire quality matters

Worn-out tires can decrease your vehicle’s fuel economy, prevent good handling, reduce traction and make driving uncomfortable. Even worse, they can increase your stopping distance.

Research from AAA reveals that driving on relatively worn tires at highway speeds in wet conditions can increase average stopping distances by a staggering 43%, or an additional 87 feet—more than the length of a semitrailer—when compared with new tires.

So how do you know when to replace tires? A visual inspection of your tires—done once a month and before you take a long road trip—can identify potential problems before they get worse.

1. Reduced tread

Worn-out tread mean your tires can’t adequately grip the road in rain or snow, and the result can be a slippery ride. Use the “quarter test” to determine your tire tread depth, which should never fall below 1/16th of an inch.

AAA maintains that tires should be replaced once the tread depth reaches 4/32nds of an inch, which is when stopping distances have already begun to deteriorate significantly.

Conduct a simple test: