# 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](https://appointauto.com/guides/tire-puncture-repair-rules/)).
- Cracking in the sidewall or between tread blocks, a sign of age ([how old is too old](https://appointauto.com/guides/how-old-tires-dot-date-code/)).
- Uneven wear that has reached the wear bars on one edge. Fix the cause with an [alignment](https://appointauto.com/guides/wheel-alignment-signs-cost/) so new tires last.

## Find a tire shop

- [Tire shops in Los Angeles](https://appointauto.com/tire-shops/los-angeles/) — 1 listing
- [Tire shops in Oakland](https://appointauto.com/tire-shops/oakland/) — 1 listing
- [Tire shops in San Francisco](https://appointauto.com/tire-shops/san-francisco/) — 1 listing
- [Tire shops in San Jose](https://appointauto.com/tire-shops/san-jose/) — 1 listing
- [Tire shops in Santa Clara](https://appointauto.com/tire-shops/santa-clara/) — 1 listing
- [Tire shops in Sunnyvale](https://appointauto.com/tire-shops/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](https://appointauto.com/guides/how-old-tires-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?](https://appointauto.com/guides/how-often-rotate-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](https://appointauto.com/guides/new-tire-installation-cost/) — What a tire installation includes, the extra line items to expect (valve stems, TPMS service, disposal, state tire fee), and how to compare quotes.

[Find a shop near you](https://appointauto.com/)

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Source: https://appointauto.com/guides/when-to-replace-tires-tread-depth/ · Last updated 2026-10-23. Station details are compiled from public listings and can change; call the shop to confirm hours and prices before you go.