Tyres degrade in two ways: through wear, and through age. Knowing both signs helps you replace them before they become a safety risk.
Tread depth
Once your tread reaches the legal minimum (1.5mm in New Zealand), your tyre is no longer roadworthy. Many safety experts recommend replacing earlier, around 3mm, particularly for wet-weather performance. See our guide on tyre tread legality for how to check.
Visible damage
- Cracks in the sidewall or between tread blocks (often from age or UV exposure)
- Bulges or blisters, which indicate internal structural damage
- Cuts or punctures in the sidewall, which usually can't be safely repaired
- Uneven or unusual wear patterns, which may point to alignment, pressure, or suspension issues
Age — how to read the DOT code
This example reads as week 23 of 2024.
Even tyres with plenty of tread left can degrade with age as the rubber compound hardens over time. Many manufacturers recommend replacing tyres after 5–10 years regardless of tread depth, especially for spare tyres that see little use.
Not sure?
If in doubt, bring your vehicle in and we'll check your tyres for wear, damage, and age.