When to Replace Your Tires: Tread, Age, and Warning Signs
Tires wear out in two different ways, and most drivers only watch one of them. Tread depth is the obvious one. Age is the one that catches people by surprise, because a tire can look nearly new and still be past its safe life.
Here's how to check both, plus the warning signs that mean a tire is done regardless of what the numbers say.
Tread depth: the part everyone knows
New tires typically start with 10/32 to 12/32 of an inch of tread. The legal minimum in most US states is 2/32. Between those numbers, your tire is losing capability the whole way down, and the loss isn't linear.
The number that matters most is wet performance. As tread shrinks, the grooves that channel water away shrink with it. By 4/32, wet braking distances have grown substantially and the risk of hydroplaning rises fast. That's why many tire experts recommend replacing at 4/32 rather than riding down to the legal limit, especially if you drive in rain regularly. Snow needs even more: if winter traction matters where you live, 5/32 to 6/32 is where a tire stops being a winter performer.
The penny test, done right
Take a penny and insert it into a tread groove with Lincoln's head pointing down. If you can see the top of Lincoln's head, that groove is at or below 2/32 and the tire is legally worn out.
For the smarter early-warning version, use a quarter instead. Washington's head sits at about 4/32: if you can see the top of his head, you're at the point where wet performance is seriously degraded and it's time to start shopping.
Check multiple grooves across the tire, inner, center, and outer, and check all four tires. Uneven readings are their own warning sign, which we'll get to.
Most modern tires also have built-in wear bars, small raised bridges inside the grooves that sit at 2/32. When the tread wears flush with the bars, the tire is at the limit.
Age: the wear you can't see
Rubber degrades over time whether you drive on it or not. Oxygen, heat, and UV exposure slowly break down the compounds, and the internal structure weakens. An old tire with deep tread can be more dangerous than a worn newer one, because age-related failures tend to be sudden, like tread separation, rather than gradual.
The general guidance from vehicle and tire manufacturers: have tires inspected annually once they pass six years old, and replace them at ten years from the manufacture date no matter how they look. Many experts and automakers lean closer to six as a practical replacement point, especially in hot climates where degradation runs faster. A garage-kept car in a mild climate buys you time; a car parked outside in southern sun does not.
This matters most for low-mileage drivers, spare tires, and anything that sits: trailers, classic cars, the third vehicle that only gets driven on weekends. Those tires die of age long before they die of tread.
How to read the date code
Every tire carries its birth date on the sidewall inside the DOT code. Find the string starting with DOT and look at the last four digits. The first two are the week, the last two are the year. A tire stamped 3522 was made in the 35th week of 2022.
If you only see a partial DOT code with no date, check the other sidewall; the full code is often stamped on one side only. And if the date code has three digits, the tire was made before the year 2000, which means it belongs in a museum, not on your car.
Check the date code when buying, too. Tires are sold as new for a while after manufacture, and a reputable seller ships recent production. If a "new" tire arrives already several years old, you're entitled to ask questions.
Warning signs that override everything
Some conditions mean replacement now, regardless of tread or age. Cracks in the sidewall or between tread blocks mean the rubber is degrading. A bulge or bubble in the sidewall means the internal structure has failed and the tire can let go without warning. Vibration that appears suddenly, cords or fabric showing anywhere, or a tire that repeatedly loses pressure with no puncture found all belong in the same category: stop driving on it.
Uneven wear across a tire is a softer warning. Wear concentrated on the edges suggests underinflation, wear down the center suggests overinflation, and wear on one shoulder usually means an alignment problem. The tire may still have life, but whatever caused the pattern will eat the replacement too if you don't fix it first.
Replace in pairs or fours, and plan ahead
Tires should generally be replaced at least in pairs on the same axle, and if your vehicle is all-wheel drive, check your manual: many AWD systems require all four tires to match closely in wear, and mismatches can damage the drivetrain.
The best time to shop is before you're forced to. A tire that fails on the highway turns you into the least price-sensitive customer alive, buying whatever the nearest shop has in stock. Checking your tread and date codes twice a year keeps the decision on your schedule, where you can take a week and compare. When you're ready, enter your size on Treddur and we'll show you current prices from major online retailers, cheapest first.