When to replace your tyres: tread depth and age
1.6mm legal vs 3mm safe, the 6-year rule, and how to read a tyre date code.
The legal minimum tread depth in Ireland is 1.6mm across the central three-quarters of the tyre. The safe minimum is more like 3mm. Here’s how to tell where you are.
Tread depth — the 20p coin test
Insert a 20p coin into the tread groove. If you can see the rim of the coin, your tread is below 3mm — replace soon. If the rim is hidden, you have at least 3mm.
For the legal 1.6mm check, look for the tread wear indicators — small raised bumps inside the grooves. If the tread is level with the bumps, the tyre is at the legal limit and must be replaced.
Inner-edge wear
Most drivers check the centre of the tread. Inspectors check the inner edge. Wheel alignment problems wear the inner edge first — visible from inside the wheel arch but not from the outside. If your inner edge is bald and the outer edge is fine, you have a wheel alignment problem, not just a tread problem.
Tyre age
Tyres degrade chemically over time, even when not used. The DOT date code on the sidewall tells you the manufacture date — four digits, week-and-year. “2719” means week 27 of 2019.
- Tyres older than 6 years: inspect closely, replace if any sign of cracking
- Tyres older than 10 years: replace regardless of tread depth (some manufacturers say 7)
- NCT will fail tyres older than 10 years
Sidewall damage
Cuts, bulges, exposed cords — replace immediately. A bulge means the inner sidewall has been damaged (curb hit) and the tyre may blow out at speed.
Mismatched tyres
Different brands, sizes, or types on the same axle is an NCT fail. Two new tyres on the rear and old on the front of a FWD car can be safer than the reverse — but it’s better to replace in pairs.
Book a tyre check — phone 01 847 5146.