Car Tires
Car tires should be replaced after 6 to 10 years — regardless of how much tread is left. Rubber ages and turns brittle; the age is stamped in the DOT code.
Why tires have an expiry
Tires are made of a rubber compound that ages over time — even on a car that barely gets driven. Oxygen, UV light, heat and ozone harden the rubber and make it brittle. The tire loses elasticity, fine cracks appear in the tread and sidewalls, and the grip that matters most on wet roads fades. That is why tread depth is not the only thing that counts — age matters too.
As a guideline, safety agencies and tire makers recommend replacing tires after no more than ten years from the manufacture date, regardless of tread. Many recommend a check-up every year from about six years on. The same goes for the spare that sits unused in the trunk for years: it ages just like the others.
Reading the age: the DOT date code
A tire's true age is printed right on the sidewall. Look for the four-digit number at the end of the DOT code — it tells you the week and year it was built:
On the sidewall you will see "DOT" followed by several characters. The last four digits are what matter.
3223 means the 32nd week of 2023. The first two digits are the week, the last two the year.
Current year minus the year built. Check yearly from about six years, and replace by ten.
Check it yourself: the penny test
Age aside, tread depth is the other half. The legal minimum in most US states is 2/32 of an inch, but for safety you should replace well before that. A penny makes it easy:
Insert a penny head-down — if the tread covers the top of his head, you have plenty left.
Grip on wet roads is dropping — start planning a replacement.
You are at or below 2/32 in — replace immediately.
When to replace — overview
Whether a tire is still safe comes down to age, tread and condition. This table sums it up:
| Situation | Recommendation |
|---|---|
| Over 10 years old | replace, whatever the tread |
| 6–10 years old | have it checked yearly |
| Tread at 2/32 in | legal limit — replace now |
| Below 4/32 in | replace recommended (wet grip) |
| Cracks, bulges, objects | have a pro inspect it |
Make them last: storage & care
Stored seasonal tires age faster when handled wrong. A few habits help:
Store cool, dark and dry — UV light and heat speed up rubber aging.
Check pressure regularly — wrong pressure causes uneven wear and worse fuel economy.
Tires without rims stand upright and get turned occasionally; on rims, stack flat or hang them.
Away from ozone sources — electric motors and solvents give off ozone, which attacks rubber.
Common myths
Risky half-truths surround tire age:
Not necessarily — even a tire with good tread can turn brittle and dangerous as it ages.
Not always — brand-new tires can have sat in storage for years. Always check the DOT date.
It does — the spare ages just like the rest. Check it regularly too.
Built into every tire are tread wear indicators — small raised bars across the grooves. When the tread wears flush with those bars, the tire is at 2/32 in and legally worn out. The little triangle marks on the sidewall show where to look.