When to Replace Tires: Tread Depth, the Penny Test and California Law
Replace a tire when its tread is worn to 2/32 inch, where the built-in wear bars become flush with the tread, and consider replacing at 4/32 inch if you often drive in rain. California Vehicle Code 27465 makes 1/32 inch in any two adjacent grooves the legal minimum for most vehicles, but stopping distances on wet roads grow sharply well before that point. Replace any tire with a bulge, sidewall cut or exposed cords right away.
Tread depth guide
| Tread depth | What it means |
|---|---|
| 10/32 to 11/32 inch | New tire |
| 6/32 inch | Minimum for snow tires at California chain control level R-1 |
| 4/32 inch | Wet grip noticeably reduced; plan to replace (quarter test) |
| 2/32 inch | Worn out; wear bars flush (penny test) |
| 1/32 inch | California legal minimum in any two adjacent grooves |
Other reasons to replace a tire
- A bulge or bubble on the sidewall: the internal structure is damaged.
- A puncture in the shoulder or sidewall, or larger than 1/4 inch (repair rules).
- Cracking in the sidewall or between tread blocks, a sign of age (how old is too old).
- Uneven wear that has reached the wear bars on one edge. Fix the cause with an alignment so new tires last.
Find a tire shop
- Tire shops in Los Angeles — 1 listing
- Tire shops in Oakland — 1 listing
- Tire shops in San Francisco — 1 listing
- Tire shops in San Jose — 1 listing
- Tire shops in Santa Clara — 1 listing
- Tire shops in Sunnyvale — 1 listing
Frequently asked questions
How does the penny test work?
Put a penny upside down in a tread groove with Lincoln's head facing you. If you can see the top of his head, the tread is at or below 2/32 inch and the tire should be replaced.
How does the quarter test work?
Put a quarter upside down in the groove. If you can see the top of Washington's head, the tread is below about 4/32 inch, which is a good time to start shopping for tires.
Do I have to replace all four tires at once?
Not always. On two-wheel-drive cars you can replace a pair, with the new tires usually going on the rear axle. Many all-wheel-drive vehicles need all four tires within a small tread-depth difference to protect the drivetrain; check the owner's manual.
What tread depth do new tires have?
Most new passenger tires start with about 10/32 to 11/32 inch of tread. Some truck and winter tires start deeper.
Related guides
- How Old Are My Tires? Reading the DOT Date Code — The last four digits of the DOT code show the week and year a tire was made. How old is too old, why rubber ages, and what to check on spare tires.
- How Often Should You Rotate Your Tires? — Most cars need a tire rotation every 5,000 to 7,500 miles. Rotation patterns for front, rear and all-wheel drive, and why rotating saves money.
- How Much Does It Cost to Install New Tires? Mounting, Balancing and Extras — What a tire installation includes, the extra line items to expect (valve stems, TPMS service, disposal, state tire fee), and how to compare quotes.