Understanding DOT Code Structure and Components

The Department of Transportation (DOT) code functions as a tire’s manufacturing traceability identifier. It confirms plant origin, internal production coding, and — most importantly for consumers — the manufacturing date.

The DOT sequence typically contains 10–12 characters molded into the sidewall. Its structure follows a regulated format: the “DOT” prefix, a two-character plant code, a two-character size or construction code, optional internal manufacturer characters, and a four-digit date code.

For safety and age evaluation, the final four digits are the most relevant component.

Locating the DOT Code on the Tire

The full DOT code appears on only one sidewall. When the tire is mounted, that side may face inward toward the vehicle, meaning visual confirmation sometimes requires repositioning or partial rotation.

The lettering is molded — not printed — and typically sits between the bead area and shoulder. Because it is raised rubber, angled lighting improves readability. In practice, using a flashlight at a shallow angle makes the date digits significantly easier to identify.

If only a partial code appears, inspect the opposite sidewall to locate the full sequence.

Decoding the Manufacturing Date

The final four digits represent week and year of production.

• The first two digits indicate the production week (01–52).
• The last two digits indicate the year.

For example, “3219” means the tire was produced in the 32nd week of 2019.

Week numbering follows the standard calendar system. A tire produced in week 01 originates from early January production; week 52 corresponds to late December.

Tires manufactured before 2000 used a three-digit format, but those products are beyond modern service life and should not remain in operation.

Plant Code and Internal Identification

The two characters following the DOT prefix identify the manufacturing plant. Each approved facility worldwide receives a unique code registered with the U.S. Department of Transportation.

The next two characters typically reference size category or construction attributes. Additional optional characters may follow, used internally by manufacturers for quality tracking or batch identification.

These intermediate codes are primarily for traceability and recall management rather than consumer decision-making.

Tire Age, Storage, and Real-World Safety

Chronological age matters because rubber compounds degrade over time, even without use. Oxidation, ozone exposure, and thermal cycling gradually alter compound flexibility.

Most major manufacturers consider properly stored tires serviceable for 2–3 years as “new” inventory. In active service, evaluation is recommended after five years, with replacement commonly advised by six years regardless of tread depth.

Importantly, tread depth alone does not determine tire viability. Structural aging can occur while tread still appears adequate.

In real-world inspections, sidewall micro-cracking, tread separation, or stiffness under manual flexing often indicate advanced aging.

Common Reading Challenges

DOT codes may become less visible due to sidewall treatments, accumulated dirt, or protective coatings. Cleaning the area with mild detergent improves clarity.

On vehicles with tight wheel wells or dual rear wheels, accessing the full DOT code may require vehicle repositioning or professional inspection.

All tires legally sold in North America must display a complete DOT code. Missing or incomplete codes warrant immediate caution and further verification.

When This Approach Is Not the Right Choice

DOT code verification confirms manufacturing date but does not reveal storage conditions, alignment history, load abuse, or environmental exposure. A five-year-old properly maintained tire may outperform a three-year-old tire subjected to chronic underinflation or overloading.

Professional inspection remains necessary for full structural assessment. Age is one variable in safety evaluation, not a standalone verdict.

In emergency replacement situations, immediate safety takes priority over date-code analysis, though DOT verification should remain part of routine maintenance checks.

Final Perspective

The DOT code does not determine whether a tire is safe — it establishes a starting point for evaluating risk over time.

Long-term tire safety depends on the interaction between manufacturing date, storage conditions, inflation discipline, load compliance, and driving environment. The date code provides the timeline; maintenance determines the outcome.