How to read a trailer tire date code
The essential answer
A trailer tire date code is the final group of characters in the DOT serial printed on the tire sidewall. It usually appears as four digits inside an oval or a standalone box. The first two digits are the week of manufacture and the second two digits are the year. A tire marked 3221 was made in the 32nd week of 2021. Some older tires use a three-digit code, which indicates manufacture before 2000 and is now considered too old for service in most cases.
Why the date code matters
Trailer tires age out by time as well as wear. Rubber compounds lose flexibility and resistance to cracking even when the tread looks deep. Many tire industry and trailer manufacturer recommendations treat tires as candidates for replacement around five to seven years after the manufacture date, with a common practical service limit near ten years under favorable storage and load conditions. The date code, not the purchase date, starts that clock.
Where to find the date code
Look on the sidewall facing outward from the trailer. The full DOT code begins with the letters DOT followed by a series of letters and numbers. The date code is the last group. On many trailer tires it is placed on a single side only, so if it is not visible, check the inward-facing sidewall or the opposite side of the trailer. A flashlight helps when the tire is mounted and the wheel opening is small.
How to decode the four digits
Read the four digits as two pairs. For example, 2519 is week 25 of 2019. Week 01 is the first week of January; week 52 is the last full week of December. A code of 4320 means the tire was produced in late October 2020. If the code has only three digits, such as 258, treat it as a pre-2000 tire regardless of the third digit.
Trailer tire date code chart
Code | Week | Year; 0121 | 1st week | 2021; 1522 | 15th week | 2022; 4019 | 40th week | 2019; 0720 | 7th week | 2020; 5218 | 52nd week | 2018
Steps to inspect and record the date
Park the trailer on level ground and set the parking brake or chock the wheels. You do not need to raise or remove the wheel to read the sidewall. Locate the DOT string. It may continue around the curvature of the sidewall, so read the entire line rather than only the visible portion. Find the final four digits. On some tires they sit inside a small oval; on others they appear after the rest of the DOT code without a border. Record the week and year for each tire, including the spare. Do not assume all tires have the same date. Compare the recorded dates against the replacement interval recommended for your trailer tires. If the manufacturer or tire brand is unavailable, use the general five-to-seven-year inspection window as a decision point.
Completion check and safety limits
You have completed the task when you can state the calendar week and year each tire was made. If a tire shows a three-digit code, sign of weather cracking, sidewall damage, or a date beyond the service limit for your use, tire replacement or professional inspection is the appropriate next step. Do not continue using a trailer tire with visible structural aging or an unknown manufacture date when the trailer will carry significant loads at highway speed. When a tire has no readable DOT date code, a qualified tire service should inspect it before continued use.