No matter how well you take care of your car, how often you inspect it or how regularly you change the oil, there’s one part that’s going to need to be replaced regularly: The tires.

Hop from a car with old tires into a ride with new ones, and you’ll instantly feel the difference. It might be the most important safety feature on any automobile, so before you slap on that cheap replacement set, there’s a few things to consider. Putting the proper tires on your car will ensure that the speedometer is accurate and the transmission doesn’t take any loads it can’t handle — not to mention the peace of mind that comes with healthy, road-gripping wheels.

First and foremost, let’s answer the question: Do you need a new set of tires at all? Most buyers replace their tires on one of two occasions: When they get a flat or when a mechanic tells them they need it. While you’ll certainly be able to sense the change in handling as your tires lose their tread, there’s a number of easy visual cues that can alert you when your tires are on their way out.

Most modern tires come equipped with tread wear indicators. While the exact placement of the indicators can vary, they should be fairly obvious. Just look for tiny bars in the grooves of your tread, running perpendicular to the tread pattern. In a new or slightly used tire, they should be well beneath the top of the tread. Once they are flush with the outer surface of the tread, it’s definitely time to replace the tire.

Failing that, there’s an old fashioned trick to test the depth of your tread, and therefore the wear and tear on your tire. Take a penny or quarter and insert it into the deepest tread you can find on your tire, making sure to align it in such a way that you’re dipping Abe Lincoln (or George Washington) into the canyon headfirst. If you can still see the top of their head, it’s time to go tire shopping.

Newer cars can back all this up by alerting you to changes in tire pressure, but there’s still good reason to periodically check the tread up close and personal. The way your tread is worn can even be a red flag for alignment or inflation issues. Is the tread worn more on one side of the tire than the other? Get your alignment checked. Is there more wear on the shoulders (outer edges) of the tire versus the center? Your tire might be underinflated. Losing tread on the center but not the shoulders? It could be overinflated.

Once it’s time to buy a tire, you’ll find an intimidating amount of options out there. The first thing to do is take a look at your old tires. You may not want to stick with the exact type or brand as your old wheels, and that’s fine — especially if they didn’t serve you well. But you should at least get a tire with the same size and speed rating as your car’s original set. And that’s the original set, mind you — which might not necessarily be the last set of tires you had.

How do you find the size and speed rating? Look on the driver’s side doorjamb. There should be a sticker there with all the specs on your factory set of tires. Finding the numbers on a tire is a bit more complicated, but relatively easy if you know what you’re looking for. On the sidewall of any tire, you’ll find a set of numbers. To get the size, look for a prominent set of numbers and letters separated by a slash. (That’s a “/” symbol, mind you. If there’s an actual slash, maybe find another tire.) That set of characters is the size: The first letter represents the general tire type (“P” for passenger, perhaps), while the first set of numbers before the slash is the tire width in millimeters. After the slash, you’ll find another number representing the aspect ratio, then a letter that tells you what construction the tire is (“R” for radial, “B” for belted bias and “D” for diagonal bias). The number after that letter is the diameter of the wheel rim.

After all that, you should see another two or three-digit number followed by a letter. The number is your load index, a number that’s used to measure your tire’s maximum carrying capacity. The letter is your speed rating. It’s a code you can easily look up elsewhere, but in general: The higher the letter is in the alphabet, the more speed your tires can handle on a consistent basis. (Except for the “H” rating, which is somewhere in the high middle of typical tire ratings.)

If you’re feeling dizzy in the face of all that jargon, don’t feel like you need to translate it. Just remember these are the numbers you’ll need to match up from your original tires to your new ones.

Aside from the measurements, there are a vast array of tire styles to choose from. All-season tires like the Westlake RP18 are a popular, all-around choice. While not the pinnacle in terms of grip or handling, they’re more than capable for most commutes and they’ll keep that grip in rain or light snow. Performance tires are typically marketed to sports cars, with their higher handling and speed rating balanced out by a shorter tread life. Snow tires, as you might expect, are deeply grooved to handle heavy winter conditions, while summer or “three-season” tires are built for a speedier ride in either rain or sunny weather.