When to replace tires: tread, age and damage
Replace tires when tread reaches 2/32 inch, when age or dry rot makes them unsafe, or when you see sidewall damage. How to measure tread, read the DOT date code, and why miles are not the rule.
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Short answer
Replace a tire when its tread is worn to 2/32 inch (the wear bars), when it shows damage such as exposed cords, a bulge or a separation, or when it is old. There is no mileage at which every tire must go. Tire makers’ age guidance varies, and the U.S. Tire Manufacturers Association says age alone cannot predict a tire’s life, so follow your tire maker and have a tire professional inspect older tires.
Choose this if
Use a tread gauge or a penny every month, check the DOT date code once, and look at the sidewalls.
Choose the other option if
Carumi helps if you want each tire change logged with its date, mileage and receipt, so you know when the set was fitted.
At a glance
| Feature | Remembering or a note in the glovebox | Carumi |
|---|---|---|
| Records the date of the tire change | Partlyif you write it down | Yes |
| Records the mileage at the change | Partly | Yesfrom the odometer |
| Keeps the receipt and photos | No | Yeswith the service |
| Reminds you by date or mileage | No | Yeswhichever comes first |
| Measures tread depth | Noyou need a gauge or a penny | No |
| Works for several vehicles | No | Yes |
Tread depth: 2/32 inch is the limit
New tires have tread about 11/32 to 14/32 inch deep, according to Purdue Extension. When the tread reaches 2/32 inch, the tire needs to be replaced. Each tire has wear bars molded across the grooves at the 2/32 mark, and when the tread is lower than them you should replace the tire right away.
The 2/32 figure is also a legal limit in some places. Alabama’s traffic code, for example, treats a tire with less than 2/32 inch in two adjacent grooves as unsafe, and other states have their own rules, so check yours. A tire can be legal and still not be a good tire in rain.
How to measure tread at home
A tread gauge is the best tool and costs little. Push the pin into a groove at several points across the tire and around it, because wear is often uneven. If you have no gauge, use a penny.
Insert a penny into the grooves that look shallowest. If the tread covers any part of Lincoln’s head, you have at least 2/32 inch. If you can see all of his head, replace the tire. Purdue adds that a quarter works the same way for 4/32 inch, where tread covering part of Washington’s head means 4/32 or more.
- Check every tire, and several grooves on each.
- Look at the inside and outside edges, which can wear faster than the center.
- University of Alabama fleet guidance says that if only two tires are replaced, they should go on the rear axle.
Age and the DOT date code
Rubber ages even when the car sits. Sunlight, heat and ozone dry out the sidewalls, and Purdue notes the steel inside can then be exposed to moisture and salt. There is no firm rule for how old is too old. Purdue gives a rule of thumb of replacing a tire made more than eight years ago and says to check with the manufacturer, while a University of Alabama fleet guideline says most manufacturers recommend replacement at 5 or 6 years.
The U.S. Tire Manufacturers Association says that most people drive enough that tread wear replaces tires before age matters. Age is more of a factor on a spare that matches the other tires and on cars driven rarely. It also says no calendar age can predict a tire’s life, so ask a tire professional to inspect older tires.
- Find the DOT code on the sidewall: a string starting with “DOT.”
- The last four digits are the week and year made, so 3521 means the 35th week of 2021.
Damage that means replacement
Tread is not the only reason. Alabama’s traffic code calls a tire unsafe if any ply or cord is exposed, if it has a bump, bulge or separation, or if it has cracks or cuts longer than 1/4 inch and deep enough to expose the cords. Purdue says sidewall damage cannot be repaired because the tire’s strength has been compromised.
A puncture in the tread can often be repaired if the hole is under 1/4 inch, with a plug and a patch from inside the tire. Purdue advises replacing instead if the tread is at or near 2/32 inch. Have a tire shop look at any puncture.
Notice changes while driving, too. USTMA says increased air loss, noise or vibration can point to an internal problem, and asks drivers to see a tire professional right away.
Mileage is not the rule
Miles do not tell you the tread left on a particular tire. USTMA says a tire’s condition depends on time, storage and use, including inflation pressure, load, speed, temperature, impacts and road hazards, and that how the tire is maintained is probably the most important factor. On a car that is driven rarely, USTMA says age matters more than tread wear.
The reliable way is a monthly look. USTMA recommends inspecting all tires monthly, including the spare, for inflation, tread wear and damage, even if your car has a tire pressure monitor.
Log every tire change
Write down the date, the odometer reading, the tire brand and size, and the DOT code of the new tires, and keep the receipt. A record tells you how long the last set lasted and when to start checking the next, and proves the maintenance when you sell.
Rotation, alignment and balancing belong in the same record, since USTMA lists them as part of regular professional tire care.
Frequently asked questions
How many miles do tires last?
There is no single number. USTMA says wear depends on how the tire is used and maintained, so measure the tread instead of counting miles.
What tread depth means I need new tires?
2/32 inch, which is where the wear bars sit. A penny that shows all of Lincoln’s head means you are at or below it.
How old is too old for tires?
No firm rule exists. Purdue Extension suggests 8 years as a rule of thumb, a University of Alabama fleet guideline cites 5 or 6, and USTMA says to follow your tire maker and have older tires inspected.
Where is the tire’s date on the sidewall?
In the DOT code. The last four digits are the week and year of manufacture, such as 3521 for the 35th week of 2021.
Is Carumi available?
See the official app page for current availability and pricing.
Our pick
Carumi, so the tire date is never a guess
Carumi logs each tire change with its date, the odometer and the receipt, and keeps it next to oil changes and other services. Schedule a reminder by date, mileage or whichever comes first, and the record is ready if you sell the car. It does not measure tread, so keep the gauge or penny in the glovebox.
- Each service with its receipt and photos
- Reminders by date, mileage or both
- Cars and motorcycles, each with its own history
