Last updated: Reading time: 19 minInspections documented: 1,700+
Complete guide + photo gallery

Tyre Tread Depth — how to check it, and what every depth looks like

What tread depth means, how to check it in five minutes (gauge or a coin from your pocket), the 1.5 mm legal minimum vs the 3 mm we recommend, a braking-distance calculator, and real photos of tyres at every stage of wear from our own workshop archive.

1.5 mmNZ legal minimum
3 mmWhere we say replace
1,644Tyres measured by hand
43,500+Photos & videos in the archive
Check your tread now → See your stopping distance
The short answer

Tread depth is the height of rubber above the bottom of the main grooves. New car tyres have about 8 mm; New Zealand's legal minimum is 1.5 mm across the full tread width, and a tyre below it fails a WOF. Wet grip falls away fast under 4 mm, so replace at 3 mm — and check all four tyres at several points, because most wear is uneven.

  • Quick check: a 20c coin in the main groove — if the carving's chin shows, you are at 3 mm or less. A gauge is better; the tread-wear bars in the grooves are the 1.5 mm limit.
  • What it costs you: from 100 km/h in the wet, 1.5 mm of tread stops metres later than 3 mm — use the calculator for your speed and tyre type.
  • What we see: of the first 1,600 tyres we measured, the median had 3.0 mm left, 63% had a point under 3 mm and 18% had a point under the legal limit.
  • Age counts too: cracked or 6-year-old tyres are done whatever the depth reads.
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In this guide
In this guide 10 sections
Basics

What is tyre tread depth?

Tread depth is the measurement from the top of the tyre's rubber to the bottom of its deepest grooves. Those grooves are not decoration — they channel water, mud and grit out from under the contact patch so the rubber can grip the road.

New passenger tyres start at about 8–9 mm. 4WD and off-road tyres can start at 10–15 mm or more, with aggressive patterns for loose surfaces. As you drive the rubber wears and the grooves get shallower; once tread reaches 1.5 mm in New Zealand the tyre is legally worn out and must be replaced.

8 mmNew passenger tyre
4 mmMid-life — wet grip starts to fall
3 mmReplace
1.5 mmLegal minimum — WOF fail below
💡 The bars in the grooves Every tyre has small raised bars (tread wear indicators, TWI) moulded across the main grooves at about 1.6 mm. When the tread is level with them, the tyre is at the limit. Find them by the small triangle or "TWI" on the shoulder — photos in How to check.
Basics

Why does tread depth matter?

Because it decides how far you take to stop in the wet. Dry grip barely changes as tread wears; wet grip does, and it does not fall in a straight line — it holds up, then collapses.

🌧️Wet braking distance: up to +38%

From 80 km/h on a wet road, a tyre at 1.6 mm can take up to 38% further to stop than the same tyre at 3 mm.

💨Aquaplaning: about 3× the risk

Tyres at the legal minimum are roughly three times more likely to aquaplane than tyres with 3 mm or more.

⚙️Water dispersal: 15 L/s vs 2–3 L/s

A new tyre can move up to 15 litres of water a second out of the contact patch at 80 km/h. A worn one manages 2–3 litres.

✅

Will my tyres pass a WOF?Tread is one of several checks — cracking, damage, matching patterns and load/speed ratings all count. Our WOF tyre guide walks through the lot.

Read the WOF tyre guide →
Tool

How much further will your tyres take to stop?

Pick your speed and tyre type, then slide to your tread depth. Distances are for a modern car with ABS on standard asphalt; the wet figure is the one that matters.

Your current tread depth4.0mm
0 mm (bald)1.5 mm (legal)4 mm8 mm (new)
Replace soon
🌧️ Wet road52.3metresvs new: +9.2 m longer
☀️ Dry road38.1metresvs new: +1.7 m longer

Where will you stop? (wet road)

🟢 New
57.5 m
🔵 Yours
72.1 m
🔴 Legal min
94.2 m
0 m25 m50 m75 m100 m
🟢 New (8 mm)🔵 Your tyre (4.0 mm)🔴 Legal minimum (1.5 mm)

The physics & the "cliff effect" chart

Grip holds steady until about 4 mm, then collapses. That is why we say replace at 3 mm, not 1.5 mm.

0–1.5 mm: illegal1.5–3 mm: danger3–4 mm: replace soon4 mm+: safe

The physics: derived from our UBPS v3.7 braking simulator (19 physics factors, 218 benchmarks, 0.71% mean error). Tread depth uses the power law η(d) = (d/8)0.25, validated against Discount Tire, ADAC and Continental data. Each tyre category carries a compound/pattern grip modifier from ÖAMTC 2025 testing — mud-terrains use harder rubber and bigger voids, so at the same depth their wet contact patch is smaller than a highway terrain's. At 100 km/h wet with 15 mm new tread: HT stops in about 44 m, AT 47 m, MT 52 m. The tread cliff below 4 mm applies to all of them.

Want the full model with vehicle weight, ABS, road surface and reaction time? Open the Tyre Braking Simulator →

Do it

How do I check my tread depth?

Five steps, under five minutes, no tools needed beyond a coin — though a $10 digital gauge is what we use for every tyre in the archive.

  1. Find the tread wear indicators (TWI)Every tyre has small raised bars moulded into the main grooves at about 1.6 mm. Look for a small triangle or the letters "TWI" on the shoulder and sight across from there. If the tread is level with the bars, replace the tyre now.
  2. Grab a coinAny NZ coin works as a rough gauge and each measures a different depth. A 20c coin is the handy one — it sits at the 3 mm mark we recommend. See the coin table below.
  3. Put it in a main grooveUse the deep channels that run right around the tyre, not the thin sipes in the tread blocks. Push the coin down until it touches the bottom.
  4. Read the reference pointHow much of the design shows above the tread tells you the depth — each coin has its own mark (for 20c: if the carving's chin shows, you are at 3 mm or less).
  5. Check several pointsAt least three across the width (inside edge, centre, outside edge) and at two or three places round the tyre. Uneven wear is normal — different readings across the tread mean pressure, alignment or suspension issues. Then do the other three tyres.

The accurate way: a gauge in the groove

Digital tread depth gauge planted in the centre groove of a tyre
The gauge in the groove. A digital gauge planted in the centre groove — this is how every tyre in our archive is measured.
Tread depth gauge measured against the moulded wear indicator bump
Against the wear bar. The gauge measured directly against the moulded wear indicator: when tread and bump are level, the tyre is at the limit.

Finding the wear indicators from the sidewall

Moulded triangle wear indicator marker on a tyre shoulder
The triangle. A small moulded triangle on the shoulder points across the tread to the row of wear-indicator bars.
Moulded TWI letters on a tyre shoulder marking the wear indicator row
The letters. Other tyres mould TWI — Tread Wear Indicator — at the same positions. Both marks mean the same thing: sight along them to find the bars in the grooves.
📷

Not sure what you are looking at?Compare your tyre with the gallery below — 17 real tyres photographed at every depth from new to worn through.

Open the gallery →
Do it

The NZ coin test — which coin measures what?

Each New Zealand coin has a feature that sits at a useful depth. Push the coin into a main groove and see whether that feature is hidden (deeper than the mark) or showing (shallower).

New Zealand coins used for tread depth testing
Any coin from your pocket. 10c for the legal minimum, 20c for our 3 mm replace-now line, 50c / $1 / $2 for healthier tread.
Coin Depth What to look for
10c ≈ 1.5 mm Outer band visible = at the legal minimum
20c ≈ 3 mm Carving's chin visible = replace now
50c ≈ 4 mm Ship's hull visible
$1 ≈ 5 mm Kiwi's back visible
$2 ≈ 6 mm Kōtuku's wing visible

The same $1 coin at six depths

Six real tyres from the archive, one coin, six answers. Match your own tyre to the closest photo.

$1 coin in the groove: Predator Comptrax PR1, new, 7.0 mm
7.0 mmPredator Comptrax PR1, new
$1 coin in the groove: Maxxis Premitra 5, 4.4 mm
4.4 mmMaxxis Premitra 5
$1 coin in the groove: BFGoodrich Radial T/A, 3.4 mm
3.4 mmBFGoodrich Radial T/A
$1 coin in the groove: Dunlop Le Mans V, 2.0 mm
2.0 mmDunlop Le Mans V
$1 coin in the groove: Hankook Ventus Prime 3, 1.4 mm
1.4 mmHankook Ventus Prime 3
$1 coin in the groove: Goodyear Optilife — bald, 0.6 mm
0.6 mmGoodyear Optilife — bald

Top view and side view — the two you should take

NZ one dollar coin in the groove of a worn Bridgestone Turanza, top view
$1 coin, worn Bridgestone at about 3 mm. The kiwi's feet stay hidden — but only just.
Side view of the coin test on the same worn Bridgestone
The same tyre side-on. The coin barely sits in the groove.
NZ one dollar coin in the groove of a severely worn Triangle, top view
Below the legal limit. On this Triangle the coin will not seat and the kiwi is fully exposed.
Side view of the coin test on the severely worn Triangle
Side-on there is almost no groove left to hold it. This tyre is finished.
Photos

The full wear scale — one pattern, four stages of its life

Three tread patterns, each photographed at four stages: a passenger tyre, an SUV highway tyre and an all-terrain. Same pattern, same camera position, different tyres. Find your own gauge reading in a row and see what that depth actually looks like. Every photo is one real tyre measured by hand in our workshop.

Hifly HF201 — Passenger touring

A budget passenger pattern followed from factory-fresh to below the legal limit.

Hifly HF201 205/70R14 tread at 7.6 mm, new, unused
7.6 mmNew, unused205/70R14
Hifly HF201 195/65R15 tread at 4.6 mm, half worn
4.6 mmHalf worn195/65R15
Hifly HF201 195/60R16 tread at 3.7 mm, replace soon
3.7 mmReplace soon195/60R16
Hifly HF201 195/65R15 tread at 1.3 mm, illegal — wof fail
1.3 mmIllegal — WOF fail195/65R15

Bridgestone Dueler H/T 684 II — SUV highway terrain

A premium SUV highway pattern in even steps from full depth down to the legal limit.

Bridgestone Dueler H/T 684 II 265/60R18 tread at 7.6 mm, new or near new
7.6 mmNew or near new265/60R18
Bridgestone Dueler H/T 684 II 265/60R18 tread at 5.2 mm, healthy
5.2 mmHealthy265/60R18
Bridgestone Dueler H/T 684 II 265/60R18 tread at 3.3 mm, replace soon
3.3 mmReplace soon265/60R18 · Centre worn ahead of the shoulders: this one ran over-inflated.
Bridgestone Dueler H/T 684 II 265/65R17 tread at 1.7 mm, at the legal limit
1.7 mmAt the legal limit265/65R17

Dunlop Grandtrek AT22 — All-terrain

A common 4WD all-terrain. It starts deeper than a car tyre and still has usable tread at depths where a passenger tyre would be finished.

Dunlop Grandtrek AT22 265/65R17 tread at 8.1 mm, new or near new
8.1 mmNew or near new265/65R17
Dunlop Grandtrek AT22 265/65R17 tread at 6.1 mm, healthy
6.1 mmHealthy265/65R17
Dunlop Grandtrek AT22 285/60R18 tread at 4.7 mm, half worn
4.7 mmHalf worn285/60R18
Dunlop Grandtrek AT22 265/65R17 tread at 3.2 mm, finished
3.2 mmFinished265/65R17 · Worn into the shoulder with wire showing: an instant fail whatever the depth reads elsewhere.
⚠️ Depth is not the only thing that fails a tyre The Dunlop above still reads 3.2 mm in the centre and is finished, because the shoulder is worn to the wire. Cracking, cuts, bulges and exposed cord fail a WOF at any depth — check the whole tyre, not just one groove.
Buying

Below 3 mm? Here is what replacing them looks like

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📐

Not sure of your size?It is on the sidewall — 205/55R16 and so on. Put it in the size calculator and it shows what fits, plus alternatives.

Open the size calculator →
Questions

Common questions about tread depth

Will uneven tyre wear fail WOF even if tread is above 1.5mm?

⚠️ Yes — if the worn area falls below 1.5mm, even if the rest is fine.

The 1.5mm rule applies in every principal groove that normally carries a moulded wear indicator, around the entire circumference (three-quarters of the tread width is only the fallback the manual uses for a tyre with no moulded indicators). So if one edge is worn to 1mm while the centre is 5mm, the tyre fails.

Common uneven wear patterns:

  • Inner edge wear: Usually alignment — too much negative camber or toe-out
  • Outer edge wear: Hard cornering, positive camber, or toe-in
  • Centre wear: Over-inflation
  • Both-edge wear: Under-inflation

Inspector may also note: Severe uneven wear indicates an underlying mechanical issue (alignment, suspension). They may advise getting it checked even if tread is still legal.

What tread depth do you recommend for NZ wet roads?

We recommend replacing tyres at 3mm — well above the legal 1.5mm minimum. Here's why the difference matters enormously on NZ's wet roads:

Tread Depth Wet Braking at 80 km/h Aquaplaning Risk Status
8mm (new) ~25m stopping distance Low ✅ Full performance
3mm ~34m (+36%) Moderate ⚠️ Replace soon
1.5mm (legal min) ~43m (+72%) High ❌ Dangerous in rain

At 1.5mm, a tyre at 80 km/h needs 18 metres more to stop than at 8mm — that's roughly 4 car lengths. In Bay of Plenty and Waikato where rain is frequent and roads are often chipseal, grip deteriorates rapidly below 3mm.

🛑 Braking Distance Calculator — see how tread depth affects YOUR stopping distance | ✅ WOF Tyre Guide

How do I measure tread depth with a coin in NZ?

The NZ 20-cent coin test is the quickest way to check tread depth without a gauge:

1. Take a New Zealand 20-cent coin

2. Insert it into the main tread groove with the number "20" facing down into the groove

3. If you can see the entire "20", your tread is at or below approximately 2mm — time to replace

4. If the "20" is partially hidden by the tread, you still have usable depth

Important: Check at least 3 points across the tread width (inner edge, centre, outer edge) and at multiple points around the tyre. Uneven wear can mean one spot is at 2mm while another is at 5mm.

For more accuracy: A proper tread depth gauge costs $5–15 from any auto parts store and reads to 0.5mm precision. Worth having in the glovebox alongside your tyre pressure gauge.

✅ WOF Tyre Guide — see exactly what inspectors measure and where

What is the legal minimum tread depth in New Zealand?

1.5 mm across the full width of the tread that normally contacts the road, on every tyre. Below that a tyre fails a Warrant of Fitness and is illegal on public roads. We recommend replacing at 3 mm, because wet-weather grip drops steeply below that point — see the calculator above.

When should I actually replace my tyres?

At 3 mm for safety, not the 1.5 mm legal minimum. At 3 mm wet braking distances are already clearly longer than new. For winter driving or lots of motorway use consider 4 mm. Replace tyres regardless of tread if they are more than 5–6 years old (check the DOT date code), or show cracking, bulging or uneven wear.

What causes uneven tyre wear?

Centre wear (middle wearing faster) = over-inflation. Both edges wearing = under-inflation. One-sided wear = wheel alignment (camber or toe). Cupping or scalloping = worn suspension. Diagonal wear can mean a bent wheel or suspension damage. Rotating every 10,000 km evens wear out. In our first 1,600 inspections about 1 in 4 tyres with a wear pattern recorded were wearing unevenly — 195 on one edge (alignment), 120 on both edges (under-inflation), 31 in the centre (over-inflation).

How do I find the tread wear indicators on my tyre?

Look for small raised bars about 1.6 mm high moulded into the main grooves. To find them, look on the sidewall for a small triangle, the letters TWI, or a brand mark (Michelin uses its Bibendum mascot) — sight straight across the tread from that mark. When the tread surface is level with the bars, the tyre is at the legal minimum.

How long do tyres typically last in New Zealand?

40,000–80,000 km is typical for quality passenger tyres with normal driving. Driving style, roads, vehicle weight, tyre quality and inflation all move that. High-performance tyres wear faster (20,000–40,000 km); touring tyres last longer. Whatever the tread, replace tyres over 5–6 years old — rubber degrades even when the car is parked.

Can I mix different tread depths on my car?

Keep differences small, especially on the same axle. For a WOF, tyres on the same axle should have matching tread patterns and similar wear. A new tyre paired with a worn one unbalances handling and braking. On 4WD and AWD vehicles keep all four within 2–3 mm of each other to protect the differentials. Replace in pairs (same axle) or sets of four.

Does tread depth affect fuel economy?

Slightly. New, deep tread has a little more rolling resistance, so economy improves marginally as a tyre wears — but the extra stopping distance and aquaplaning risk of worn tread are not worth the few percent. Correct inflation matters far more for fuel economy than tread depth.

How does tread depth differ between passenger and 4WD tyres?

Passenger tyres start at 7–9 mm with a shallower, smoother pattern for comfort and economy. SUV highway tyres 8–10 mm. All-terrains 10–12 mm with more aggressive blocks. Mud-terrains 12–18 mm with deep, chunky lugs. Deeper off-road tread clears mud and grips loose surfaces, but wears faster on sealed roads.
Behind it

Where do these photos and numbers come from?

Our own tread depth database — every tyre that comes through the Te Puke workshop, measured by hand with a digital gauge and photographed from the same positions. It is the foundation for this guide, the braking calculator and our research reports.

1,644Tyres documented
43,500+Photos & videos
133Brands
255Distinct sizes
527Pattern names

Counts as at 19 August 2026. Of the first 1,600 tyres measured, the median had 3.0 mm of tread left, 63% had at least one point under 3 mm and 18% had a point under the 1.5 mm legal minimum — these are tyres that came off cars, so they skew worn.

Built on this database: The Workshop Tyre Report: First 1,500 Inspections · Tyre Pressures and Inflation Wear · Load Ratings and Load Capacity · Tread Pattern Direction · Tyre Research Hub · Dataset licensing

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The research behind this guide
  • Legal minimum tread depth and WOF tyre requirements: NZTA Vehicle Inspection Requirements Manual, tyres and wheels section — vehicleinspection.nzta.govt.nz
  • Wet braking, aquaplaning and water-dispersal figures: published tyre-industry test data (Continental, ADAC, ÖAMTC 2025) as compiled in our UBPS v3.7 braking model; the calculator's tread-depth law is validated against Discount Tire, ADAC and Continental datasets.
  • First-party: all photographs, gauge readings, wear-pattern counts and database figures on this page are from our own workshop inspections (1,644 tyres, 43,500+ photos and videos as at 19 August 2026). Photographs © Taylor Houghton.

Page © 2026 Tyre Dispatch NZ · Te Puke, New Zealand.

About the author
TH

Taylor Houghton

Manager, Tyre Dispatch · Warehouse Manager, Traction Tyres

Petitioner to Parliament · tyre labelling Tyrewise launch video Te Puke, Bay of Plenty workshop

Taylor Houghton has spent his working life in the tyre trade, beginning in his father's tyre business at the age of five and handling import containers through his school years. He developed Tyre Dispatch, the retail arm of Traction Tyres, and now manages it alongside the Traction Tyres warehouse in Te Puke, with responsibility for buying and brand selection. He holds no ownership interest in either business.

Both brands the company distributes exclusively in New Zealand, Anchee and Predator, were his selections, each assessed on factory accreditation, compound composition and independent test data rather than name recognition. More than 100,000 Anchee tyres have since been sold here, and both brands hold five star review averages.

The guides, calculators and tools on this site are his own work, as is the workshop dataset behind them, which covers 1,700+ documented tyre inspections and 45,000+ photographs and represents more than a thousand hours, the majority outside business hours. He is the petitioner to Parliament for mandatory tyre performance labelling and minimum wet-grip standards in New Zealand, and appeared in the launch video for Tyrewise, the national tyre stewardship scheme.

Photography, measurements and advice on this site are first-hand; where a figure comes from elsewhere, it is attributed.

1,700+Documented inspections
45,000+Workshop photos
130+Brands catalogued
25+Free tools & guides
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Looking for tyre training data? The imagery and structured inspection dataset are available to licence. Contact email@tyredispatch.co.nz.

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General guidance based on published standards and our own workshop data — reliable but hand-compiled and not guaranteed error-free. Spot something wrong? Email email@tyredispatch.co.nz and we'll fix it.

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