How to Read Full DOT Sidewall Codes: Plant IDs, Mold Serials & Date Stamps

The Department of Transportation (DOT) serial number stamped into every highway tire is far more than an arbitrary string of numbers. Mandated by 49 CFR Part 574, this code serves as the universal passport of tire manufacturing—revealing plant location, size code, mold batch, and exact production date.

1. Anatomy of the DOT Serial Sequence

A full DOT serial number consists of 3 distinct sections:

DOT [1C3B] [M6X] (3822)

1. Plant Code (1C3B)First 2-3 characters indicate the country & factory plant location.

2. Size & Mold (M6X)Optional 2-4 character internal manufacturer mold code.

3. Date Stamp (3822)4-digit capsule showing week (38) and year (2022).

2. The 2015 NHTSA 3-Digit Plant Code Standardization

Prior to April 2015, plant codes were 2 characters long (e.g. 1C for Michelin France or 3Q for Continental Germany). As global tire manufacturing expanded, NHTSA exhausted 2-character alphanumeric combinations and introduced 3-digit plant codes prefixed with numbers (e.g. 1C3 or 101).

Older 2-digit plant codes remain valid for tires produced on existing tooling, while new factory lines receive 3-digit plant codes.

3. Pre-2000 3-Digit Date Codes vs Modern 4-Digit Codes

Tires manufactured before the year 2000 used a 3-digit date code where the first two digits indicated the week and the last digit indicated the year (e.g. "388" indicated the 38th week of 1988 or 1998). Since 2000, all tires use a strict 4-digit date code.

⚠️ CAUTION: Any tire with a 3-digit date code is over 26 years old and presents an extreme risk of catastrophic structural blowout. Do not mount or drive on 3-digit date tires.