The short answer
Replace tires when tread wears to 2/32 inch (the legal minimum) — but safety experts urge replacing at 4/32 inch, where wet and snow grip drops off. Also replace any tire at 6 years regardless of tread, and never use one past 10 years, because rubber degrades with age.
What tread depth means it's time for new tires?
The legal minimum is 2/32 inch, but waiting that long is risky. Safety organizations recommend replacing tires at 4/32 inch, where stopping distance in rain and snow grows sharply. New tires start around 10/32 inch, so 4/32 leaves a clear, safer margin before grip collapses on wet roads.
| Tread depth | Status | What to do |
|---|---|---|
| 10/32"–6/32" | Healthy | Keep monitoring |
| 4/32" | Wet/snow grip dropping | Replace soon (quarter test) |
| 2/32" | Legal minimum / bald | Replace now (penny test) |
The federal tire-safety guidance from the NHTSA sets 2/32 inch as the wear limit and explains how to read the markers.
How do you check tire tread with a coin?
Two coins give you a quick read. The penny test flags the 2/32-inch legal minimum: if Lincoln's full head shows, the tire is done. The quarter test catches the 4/32-inch safety threshold earlier — if Washington's full head shows, plan to replace soon. Built-in wear bars confirm both readings.
- Penny test: insert a penny, Lincoln's head down. Seeing the top of his head means 2/32 inch or less — replace immediately.
- Quarter test: insert a quarter, Washington's head down. Seeing the top of his head means 4/32 inch — replace soon.
- Wear bars: when the molded bars sit flush with the surrounding tread, the tire is at the limit.
Do tires need replacing based on age, not just wear?
Yes. Tires age out even with healthy tread. Most manufacturers and NHTSA advise replacing tires at 6 years and never running them past 10 years, because rubber hardens and cracks over time, losing grip and risking failure. Check the four-digit DOT date code on the sidewall to find each tire's age.
- The last four digits of the DOT code are the week and year of manufacture (e.g., "2419" = week 24 of 2019).
- Look for sidewall cracking, dry rot, or bulges — all signs to replace early regardless of date.
- A spare or low-mileage tire still ages; check older cars even with deep tread. See what to check before buying a used car.
What are the warning signs that tires are worn out?
Beyond tread depth, watch for vibration at speed, longer stopping distances, and visible damage. Uneven wear often points to an alignment or inflation problem rather than age. Keeping tires inflated to the door-jamb spec and rotated on schedule helps them wear evenly and last their full life.
- Vibration, thumping, or pulling to one side.
- Uneven wear across the tread — check alignment and pressure.
- Exposed wear bars, cords, or sidewall cracks.
- A persistent TPMS warning light from chronic low pressure. Rotating tires — see how often to rotate tires — evens out wear.
Frequently asked questions
What is the penny test for tire tread?
Insert a penny into the tread groove with Lincoln's head pointing down. If you can see the top of Lincoln's head, your tread is at or below 2/32 inch — the legal minimum — and the tire should be replaced. For an earlier warning, use a quarter, which flags 4/32 inch.
Do tires expire even if they look OK?
Yes. Rubber degrades with age regardless of tread. Most tire makers and NHTSA recommend replacing tires at 6 years and never using them past 10 years, even if they look fine. Check the DOT code on the sidewall — the last four digits are the week and year of manufacture.
How do I know if my tires are bald?
A bald tire has tread at or below the 2/32-inch legal minimum, exposed wear bars flush with the tread, and reduced grip in the rain. Use the penny test, look for the molded wear-bar strips across the grooves, and watch for vibration, longer stopping distances, or visible cords.
Is 4/32 tread depth enough for winter driving?
It is the practical minimum for winter. Safety experts recommend replacing tires at 4/32 inch because grip in snow and slush drops off sharply below that. For regular winter driving, replace at or before 4/32 inch, or fit dedicated winter tires, which use softer rubber and deeper tread for cold-weather traction.
Sources
CarsLens is editorial guidance, not individualized advice. This page draws on NHTSA and AAA.