California's minimum tread depth is 1/32 inch

What Vehicle Code §27465 says

The general rule for use on a highway is the statute's own sentence: “One thirty-second (1/32) of an inch tread depth in any two adjacent grooves at any location of the tire, except as provided in paragraphs (2) and (3).”

• 4/32 of an inch tread depth at all points in all major grooves on a tire on the steering axle of any motor vehicle specified in §34500, and 2/32 of an inch tread depth at all points in all major grooves on all other tires on the axles of these vehicles.
• 6/32 of an inch tread depth at all points in all major grooves on snow tires used in lieu of tire traction devices in posted tire traction device control areas.

A dealer or a person holding a retail seller’s permit shall not sell, offer for sale, expose for sale, or install on a vehicle axle for use on a highway a pneumatic tire below the depth in subdivision (b). That does not apply when someone, as part of an emergency service to a disabled vehicle on a highway, installs a spare the disabled vehicle was equipped with. Use on a highway below those depths is prohibited, with the same temporary exception.

Tread depth is not measured where tie bars, humps, or fillets are located. The section does not apply to implements of husbandry. Subdivision (e) says the department may adopt regulations with more stringent tread-depth requirements for the vehicles defined in §§322 and 545, and different tread-depth requirements for the vehicles listed in §34500. Those regulations were not surveyed for this page on 2026-10-16.

The 18/32 inch deep-tread exclusion and the 8/32 inch competition-tire condition later on this page come from the Replacement Tire Efficiency Program’s definition of a replacement tire. They are not the minimum for driving or selling a tire. The efficiency program does not set the depth in §27465.

Statute Vehicle Code §27465, California Legislative Information. Checked 2026-10-16. The live page returned a Cloudflare challenge that day. The quotation is from the Internet Archive capture of that official page, 2025-04-20. The same words are on california.public.law, which records an access of the official page on 2026-10-12. The section says it was last amended by Stats. 1990, Ch. 71, effective May 1, 1990. On the official page the fraction is a superscript numeral, a slash, and a subscript numeral. §34500 is the cross-reference in paragraph (b)(2); this page does not restate that section.

The industry asked for exactly this to be loosened, and was refused

This is not an oversight anyone missed. SEMA and the Off-Road Business Association filed a comment asking the Commission to widen the carve-out to tires 33 inches or larger with a speed rating of R or lower — the specific change that would have swept in most of the popular lifted-truck fits. They asked for the "34.5 inches" figure to become "33 inches" and "Q or lower" to become "R or lower."

The Commission declined, finding in its adopting resolution that none of the comments received justified changing the July 17 text.

So when someone tells you the aftermarket got taken care of: partly. SEMA did win real concessions in July — competition tires, large off-road tires, all-season winter performance tires, and the rim-diameter threshold moving from 12 to 13 inches were all added in that revision, and SEMA acknowledged as much on the record. The 33-inch ask is the one that did not land.

Comment SEMA and ORBA filing, TN 271777. Commission adopting resolution, TN 272046.

Before anything else: this is a 2029 problem

Everything below applies to tires manufactured on or after January 1, 2029. Nothing on your truck today is affected, nothing you buy between now and then is affected, and tires manufactured before the cutoff stay legal to sell with no end date. If you are running a build right now, this changes nothing about it.

Regulation §3301(a), §3306(a)(1).

Four ways a custom fitment can fall outside the standard

These are exclusions from the definition of "replacement tire" — if a tire meets one, the standards never reach it at all.

1. Load index 122 or greater. Or, where the load index is not marked, rated for a maximum load above 1,450 kg. This is the cleanest and most checkable exclusion for heavy-duty fitments, and it is printed right on the sidewall.
2. Deep tread — 18/32" or greater. Many aggressive mud-terrain tires land here. Worth measuring rather than assuming.
3. Large off-road — speed rating Q or lower AND diameter 34.5" or greater. Both, not either. See the callout above.
4. Not capable of sustained speeds above 50 mph. A narrow category, but it exists.

Also fully excluded and relevant to this crowd: tires for off-road motorized recreational vehicles — dune buggies, ATVs and recreational off-highway vehicles as defined in Vehicle Code §500 — plus motorcycle tires, retreads, used tires, spares, and rims 13 inches and under.

Regulation §3302(a)(46)(A)–(O).

Competition tires: all four conditions, not one

The competition exclusion is real but tightly drawn. A tire qualifies only if it meets every one of these:

• Tread depth of 8/32" or less
• Speed rating of W, Y or (Y)
• UTQG treadwear grade of 200 or less
• Not marketed as all-season

That is a genuine track tire or an extreme-performance summer tire. A 300-treadwear extreme-performance street tire does not qualify, and neither does anything wearing an all-season marketing claim.

Regulation §3302.

If your tire is regulated, it may still have room

Being covered is not the same as being squeezed. The regulation sets six different ceilings, and several of the categories that matter here get more headroom than a standard passenger tire:

Note the 2033 column: light truck tires get the more lenient Phase 2 number (7.8) compared with a standard passenger tire (7.1). And ultra-high-performance tires get the most headroom of any category in both phases — which is not the outcome most enthusiast commentary predicted.

Regulation §3306(a)–(f).

LT tires are squarely covered

There is no argument to be had here. Light truck and commercial tires — identified by an LT prefix or a C suffix on the sidewall — have their own standard at §3306(e). The Commission's Initial Statement of Reasons is direct about intent: the statute requires tires designed for light-duty trucks to be covered, and the definition is meant to be broad specifically to eliminate loopholes between light-duty trucks and passenger cars. The vehicle cutoff is 10,000 lb GVWR.

Commission Initial Statement of Reasons, TN 269619.

How to actually check your own tire

1. Read the sidewall first. Load index, speed rating and the LT or C marking are all printed there, and three of the four exclusions above turn on exactly those numbers.
2. Measure tread depth if you are near 18/32". Do not estimate it from a spec sheet.
3. Check overall diameter, not nominal size. A "35-inch" tire is frequently not 35 inches, and 34.5 is a threshold.
4. Do not compare a published rolling resistance number to the table above. These limits are EU correlated coefficients, and a raw ISO 28580 figure is a different number. The Commission's conversion is EU correlated RRC = (0.9605 × uncorrelated) − 0.3828.
5. In 2029, the real check is the database. Retailers may only sell models listed in the Commission's database of approved tires, which makes that list — not any calculation you do — the operative answer.

Sources

• CEC TN 271526 — adopted express terms (July 17, 2026)
• SEMA and Off-Road Business Association comment, TN 271777
• CEC TN 272046 — adopting resolution
• CEC TN 269619 — Initial Statement of Reasons
• Vehicle Code §27465 — minimum tread depth. Quotation checked 2026-10-16 against the 2025-04-20 archive of that page.

Quotations from the Replacement Tire Efficiency Program were read from the filings in docket 26-TIRE-01, not from press coverage of them. The tread-depth minimums were read from Vehicle Code §27465; the check is dated in the source line under that section. This is reporting, not legal advice. If your build turns on a borderline call, the sidewall and the eventual database are the authorities, not a website. Found an error? Tell us.