Tyre safety · New Zealand
Wet roads & tyre tread depth in New Zealand
NZ's legal minimum tread is 1.5 mm across most of the tread pattern for a Warrant of Fitness. Wet-weather grip typically starts falling well before that — many NZ drivers replace at around 3 mm as a safety margin. Here's what to check and when.
Legal minimum: 1.5 mm across most of the tread pattern for most passenger tyres, under the Land Transport Rule: Tyres and Wheels 2001 (enforced via WOF). Source: NZTA Waka Kotahi.
Why wet roads matter
On wet roads, the tread grooves have to clear water out from under the tyre so the rubber can stay in contact with the tarmac. When tread depth drops, the tyre can't clear as much water — grip falls and braking distances get longer. This effect starts gradually well before you hit the 1.5 mm legal minimum.
Simple tread-depth guide
| Remaining tread | What it means in NZ |
|---|---|
| ~8 mm (new) | Full grip. Best water clearing. |
| ~3 mm | Common replace-soon threshold. Wet grip starts to drop noticeably. Plan a replacement. |
| 1.5 mm | NZ legal minimum for most passenger tyres. Any lower fails WOF. |
| Below 1.5 mm | Illegal to drive. Replace immediately. |
3 mm is common industry safety guidance — not a second legal limit.
How to check your tread
- Tread wear indicators (TWIs): small raised bars inside the grooves. When the tread wears down flush with the TWIs, you're at 1.5 mm — replace now.
- NZ 20c coin test: insert a 20c coin into the tread groove. If the outer band of the number "20" is visible, you're getting close to the wear indicators — time to plan a replacement.
- Even wear: check across the width of the tyre, not just the centre. Uneven wear can point to an alignment issue.
Coming up for a WOF? Get the tread checked before your booking — replacing before a WOF is usually cheaper than a re-check fee. If you're replacing, TyreMatch can help you get private quotes from local NZ shops.
Time to replace? Get private quotes.
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