Tire cracking and ageing guide

What cracking can and cannot tell you

Visible cracking is a condition warning, not a measurement that can prove whether the tire is structurally serviceable. Weather, heat, flexing, inflation history, impacts and storage can all matter, while internal damage may not be visible from the outside. Do not turn crack width or depth into a home-made safety grade.

• Stop normal use and arrange professional help if cords are visible, a bulge or separation appears, pressure repeatedly drops, or new vibration or noise begins.
• Have any cut, crack, impact or suspected damage inspected by a trained tire professional. An off-wheel inspection may be needed to see the inner liner and hidden structure.
• Use the vehicle placard pressure and the tire and vehicle makers’ limits. A calculator or visual check cannot approve continued use.

A safer inspection sequence

1. Park safely and inspect both sidewalls, the tread, shoulders and grooves in good light. Do not crawl under an unsupported vehicle.
2. Look for cracks, cuts, bulges, exposed cord, missing rubber, uneven wear and objects in the tread.
3. Check cold pressure against the vehicle placard. Repeated pressure loss needs diagnosis, not repeated topping-up.
4. Read the complete DOT Tire Identification Number and note the manufacturing week and year.
5. Ask a tire professional to inspect uncertain damage, especially after an impact or when the inner sidewall is hard to see.

Read the DOT TIN date field correctly

For tires made since 2000, the final four digits of the complete DOT Tire Identification Number are the date field: the first two digits are the manufacturing week and the last two are the year. For example, 3521 means week 35 of 2021. It does not identify the day and should not be converted into an exact calendar date.

NHTSA notes that the complete TIN may appear on only one sidewall, so check both sides. The preceding groups identify the plant and manufacturer-specific tire information, and the required format has changed over time. Do not use a generic pattern such as “XXXXXX YYYY” to infer an exact size or model; use the full marking and manufacturer or recall records.

Age is one input, not a verdict

NHTSA says some vehicle and tire makers recommend replacement at six to ten years regardless of treadwear. The exact maker guidance for the tire and vehicle controls. A younger tire can still be damaged, and an older tire needs closer attention even when tread remains. Include the spare in the same age and condition check.

What not to conclude

• Plenty of tread does not prove that an aged or damaged tire is serviceable.
• Holding pressure while parked does not rule out structural damage or failure under load.
• A shallow-looking surface crack does not reveal the condition below the rubber or on the inner sidewall.
• Age alone does not diagnose a tire, but it must not be ignored when condition or performance changes.

Continue with the right check

Use the tire age guide for date and maker-specific age boundaries, the sidewall damage guide for immediate damage triage, and the tire storage guide for storage practices. None replaces an in-person inspection.