Read the DOT sidewall code: the last four digits show week and year of manufacture, telling you a tire’s age.
Buying or checking tires gets easier once you can read the sidewall. The DOT string—also called the Tire Identification Number—stores the production week and year in its last four digits. With a quick glance and a little practice, you can spot fresh stock, avoid aged spares, and log the right info for recalls.
How Tire Dating Works In Plain Terms
Tires sold in the U.S. carry a DOT block that ends with four digits. Those digits map to week and year. A code ending in 2321 means the 23rd week of 2021. That tiny stamp is the fastest way to judge how long the rubber has been around, no tread gauge required.
Quick Reference: Common Date Endings
Use these patterns to get up to speed before you crawl around the car.
| Code Ending | Week | Year |
|---|---|---|
| 0124 | 01 | 2024 |
| 2321 | 23 | 2021 |
| 4518 | 45 | 2018 |
| 3515 | 35 | 2015 |
| 5109 | 51 | 2009 |
| 229▵ | 22 | 1990s (triangle mark = 1990s) |
How To Check Tire Age, Step-By-Step
Grab a flashlight and take a slow lap around the vehicle. You only need one clean look at the full DOT string on each tire.
1) Find “DOT” On The Sidewall
Look for the block that starts with DOT. The full string may face inward on one wheel; if you don’t spot the date on the outer side, check the inner side. On trucks and SUVs, turn the steering to lock for better access up front.
2) Read The Final Four Digits
Split the last four numbers into two pairs. The first pair is the week (01–52). The second pair is the year. So 3520 means week 35 of 2020. If you see a space or small oval around those digits, that’s normal—makers often frame the date to help you find it.
3) Log The Full TIN
Snap a photo of the entire DOT string on each tire. Keep it with your service notes. If a recall ever pops up, that photo speeds up verification and replacement.
4) Watch For Pre-2000 Three-Digit Codes
Older tires can show just three digits. The first two are the week, and the last digit is the year within a decade. A small triangle after the digits points to the 1990s. If you find a three-digit date, that tire is far beyond a normal service window, even if tread looks deep.
Where Makers Put The Date And What Those Letters Mean
The DOT block holds more than a date. You’ll also see a plant code, size code, and type code ahead of the final four digits. That extra data helps with plant lookups and service bulletins. For aging checks, the week-and-year ending is the part that matters day-to-day.
Freshness Benchmarks You Can Use
Retailers move inventory at different speeds. A set produced in the past 12 months is common at busy shops. Specialty sizes and low-volume patterns can sit longer in warehouses. The date is still valid; weigh that against price, availability, and your driving needs. If you want the newest batch, ask to see the sidewall on the exact tires being mounted.
How Aging Shows Up On Real Tires
Rubber dries, hardens, and loses grip with time. Heat, sun, and low pressure speed the process. Visual checks help, but the date removes guesswork. Use both.
Common Signs To Watch
- Fine surface lines at the sidewall or between tread blocks.
- Stiff feel when you press a fingernail into the rubber.
- Weather-checking around raised letters and numbers.
- Noise and vibration that appeared after storage.
- Uneven wear from low pressure or long sits.
Safety Cutoffs And Replacement Windows
Vehicle makers publish their own limits for time in service. Many shops steer drivers toward new rubber around the six-year mark and set ten years from build date as a firm stop. That range assumes normal use and proper upkeep. High heat, heavy loads, and long storage shorten that window.
Legal Format For The Date Code
U.S. rules define the week-and-year pattern. The first two symbols are the week count and the last two are the year. Weeks run Sunday through Saturday. The year’s last week may include up to six days from January of the next calendar year. This is why a code near New Year’s can look off by a few days.
Why Sidewall Location Matters
Many tires show the full date on just one side. Mounting can hide that side. If a shop rotates or flips tires, the date can land inside. That’s normal. You can still read it by turning the wheel out, using a mirror and light, or asking a tech to bring the stamp into view on a lift.
How To Shop Smart With Date In Mind
Ask to see one tire from the exact SKU you’ll receive. Read the digits yourself. If the code points to a build more than a year or two back and that bugs you, request a fresher batch. For niche sizes, be flexible on the range or pick a different pattern with stronger turnover.
Spare Tires And Low-Mileage Cars
Spare wheels often hide in trunks or under SUVs for years. They stay out of sun and look fine, yet the date still counts. Many roadside failures trace back to aged spares fitted during a puncture. Read the date on the spare, air it up during service visits, and include it in your rotation plan if it’s a full-size match.
Seasonal Sets, Trailers, And RVs
Track-day sets, winter sets, and trailer tires can age while parked. Store them clean, bagged, and out of direct sun. Keep pressure up while in storage, and roll each tire a quarter turn each month to avoid flat spots. On heavy trailers and RVs, time limits arrive sooner because of load and heat cycles.
Reading Date Codes On Imported Tires
Many non-U.S. models still stamp the same four-digit week-and-year format at the end of the DOT string. If you also spot an E-mark, that’s a European approval mark; it doesn’t change how you read the U.S. date stamp.
Helpful Sidewall Math
Need to ballpark age at a glance? Subtract the two-digit year from the current year, then check the week against today’s week number. A 2119 tire is from 2019; if this week is later than 21, add a small fraction of a year. When buying, round up so you don’t underestimate age.
Care Tips That Slow Aging
Pressure: Set cold pressures to the door-jamb label. Low pressure builds heat and ages rubber faster.
Rotation: Follow your vehicle’s pattern and interval. Even wear keeps more rubber in touch with the road.
Storage: Clean with mild soap, dry fully, and bag sets you won’t use for a while. Shade and airflow help parked cars. Avoid long sits right next to hot equipment.
Checklist: What To Record During An Inspection
Bring your phone, a tire gauge, and a paint marker. Snap the TIN, mark any scuffs, and note pressures while the tires are cold. This quick record turns into a handy baseline for your next visit.
| What You Note | What It Means | Action |
|---|---|---|
| DOT ending 0124 | Week 01 of 2024 | Fresh stock |
| Sidewall micro-cracks | Weathering from age or UV | Plan replacement |
| Tread under 4/32 in | Low wet grip margin | Shop soon |
| Uneven shoulders | Alignment or pressure issue | Correct setup |
| Stored spare dated 3515 | Built mid-2015 | Replace before use |
| Mismatched ages | Different build weeks across axle | Pair rears or fronts |
Edge Cases And Special Situations
Retreads
Commercial retreads keep the original casing and add a new tread. The DOT date marks when the casing was born, not when the new tread was applied. If you run retreads, track both casing age and retread date from the supplier’s tag.
Motorcycles
Two-wheel tires still carry the same week-and-year ending. Because bikes rely on a small contact patch, riders often chase fresher batches, especially on high-performance compounds that harden with time.
Off-Road Toys
ATVs and side-by-sides see mud, sun, and storage swings. Even with chunky lugs, the sidewall compound ages the same way. A quick date check before trail season saves hassle far from home.
Practical Examples You Can Copy
Reading A Date On A Daily Driver
You check a sedan and see DOT … 2319. That set was built in the 23rd week of 2019. If it’s late 2025 where you live, you’re past six years. Budget for new rubber and book an alignment with the install.
Spotting An Aged Spare Before A Road Trip
The spare shows DOT … 5109. That’s late 2009. It might hold air, yet it’s out of time. Replace before any long drive and set the new spare to the same pressure as the other tires on that axle.
Choosing Between Two Batches At A Shop
The counter has 4522 and 0924 in the same model. Both are unused. Pick 0924 for the fresher compound unless the older batch carries a steep discount you want. If you drive hard in heat, newer stock is the better bet.
When To Ask A Pro
If the string is scuffed or half missing, a technician can unmount the tire to expose the inner side or read it with the wheel on a lift. They can also measure hardness with a durometer and advise based on your use. For RVs and heavy trailers, ask the shop to check load rating and date together.
Helpful Links From The Rulemakers
U.S. rules define the four-digit format in 49 CFR 574.5. For care and buying tips, see NHTSA’s TireWise. These pages back up the week-and-year method and give extra context on maintenance and safety.
Bottom Line For Safer Miles
Read the four digits, spot the week and year, and weigh that age against your driving. Keep records, check the spare, and choose fresh batches when you can. Small habits here make every trip steadier.