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Minimum Tread Depth in Australia: The 1.5mm Rule Explained

Hand-drawn tyre and tread gauge title card

The legal minimum tread depth in Australia is 1.5mm. For a car, 4WD or van under 4.5 tonnes, that depth must be there across the principal grooves, the wide grooves in the part of the tyre that touches the road. You’ll see 1.6mm quoted a lot, but that’s the UK and European figure. Here, 1.5mm is the number in the rules. It’s also a floor, not a target, and your tyres will be giving you less grip in the wet well before they get there.

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TL;DR

  • The legal minimum is 1.5mm in the principal grooves, in a continuous band around the whole tyre. Not 1.6mm, which is the UK figure.
  • Tread wear indicators (small raised bars in the grooves) show when you’ve hit the limit: once they’re flush with the tread, the tyre is at the legal minimum.
  • Grip in the wet drops off gradually, so industry advice is to start planning a replacement at 3mm, not 1.5mm.
  • Uneven wear, cuts, bulges and sidewall damage can make a tyre unroadworthy even when the tread depth looks fine.
  • Check monthly with a tread depth gauge or the indicators, and book a fitter while you still have a choice of day and time.

Table of Contents

What the law says in Australia

Tyre rules sit in each state and territory’s vehicle standards, but they have been aligned for years, so the number is the same everywhere. Transport Victoria’s vehicle standards sheet says that except at the tread wear indicators, tyres need at least 1.5mm in all principal grooves. The same sheet covers vehicles up to 4.5 tonnes gross vehicle mass.

Other states say the same thing in their own words:

If you drive across borders, or move from Perth to Melbourne, nothing changes in how you measure.

Why you see both 1.5mm and 1.6mm

The 1.6mm figure comes from 2/32 of an inch and from UK and European rules. A UK fire service tyre fact card, for example, states the UK legal minimum is 1.6mm across the central three quarters of the tread. Plenty of Australian sites repeat 1.6mm out of habit. For your own tyres the safe reading is simple: the law here says 1.5mm, and anything near 1.6mm is already too close to be comfortable.

What counts as the “principal grooves”

The principal grooves are the wide grooves in the central part of the tread, the section that normally contacts the road. The depth has to be there in a continuous band that runs around the entire circumference. A single deep spot doesn’t save a tyre that is bald across a stretch of its width. That’s why a tyre can fail the rule even when the part you happened to measure looks fine.

Heavy vehicles

Trucks and buses over 4.5 tonnes GVM fall under the heavy vehicle regime, not the light vehicle sheets above. The National Heavy Vehicle Regulator’s daily check guide lists a tyre without at least 1.5mm of tread in a continuous band around the whole circumference as a fault. For heavy vehicles the band must cover at least 75% of the width that normally contacts the road, according to the research we’ve checked. If you run a light truck or commercial vehicle, confirm which side of the 4.5 tonne line you fall on before you rely on a light-vehicle checklist.

How to measure your tread depth

There are three practical methods. Use at least two on any tyre you’re unsure about.

1. Read the tread wear indicators

Every road tyre has small raised rubber bars moulded into the base of the principal grooves. When these are flush with the surface of the tread, the tyre has reached the 1.5mm limit. Look for small triangles or the tyre maker’s logo on the shoulder: they mark where the bars sit.

The catch is that an indicator only tells you about the spot where it sits. Uneven wear elsewhere across the width can make a tyre unroadworthy even while the indicator still stands proud. Treat the bars as a final warning, not a clean bill of health.

2. Use a tread depth gauge

A tread depth gauge is the most accurate manual tool, and it costs very little at an auto parts shop. Push the probe into a principal groove until the base sits flat on the tread block, then read the figure. Measure at several points across the width and at several places around the tyre, then note the lowest reading. That lowest reading is the one that counts.

Tread depth gauge measuring a tyre groove

3. Be careful with the coin test

The coin trick is common in international guides, especially the UK 20p test. The problem is that coins differ from country to country, and the UK rim depth doesn’t line up with Australia’s 1.5mm limit. If you do use an Australian coin as a rough screen, treat it as a sign to get a proper reading, not as proof the tyre is legal. For a step-by-step with photos, see our guide on how to check tyre tread depth in Australia.

If you’d rather let your phone do the first pass, our AI Tread Check is built for exactly that. A gauge is still the final word.

Why 3mm is the number to act on

At 1.5mm your tyre is legal. It isn’t necessarily safe. RACV’s advice is that tyre performance, particularly grip and aquaplaning resistance in the wet, declines progressively rather than suddenly at the legal limit, and that checking when tread reaches 3mm is a sound habit. The tread grooves are what move water out from under the tyre. The shallower they get, the less water they clear, and the longer your stopping distance on a wet road.

Here is a practical way to think about it:

Tread depth Status What to do
5mm or more Healthy Check monthly, rotate on schedule
3mm to 5mm Legal, wearing Start comparing tyres and prices
1.5mm to 3mm Legal, but wet grip is reduced Book a replacement now
1.5mm or less Below the legal limit Don’t drive further than you have to; replace

The bands in the middle two rows are our working guide, built around the 3mm advice above. They aren’t a legal standard. If you do a lot of wet-weather driving, towing or highway runs, treat 3mm as the day you buy, not the day you start thinking about it.

Roadworthy is something you maintain, not something you pass

A common trap is assuming tyres are fine because no one has told you otherwise. RACV’s tyre guidance makes the point that a vehicle’s roadworthiness is the driver’s ongoing responsibility. A tyre doesn’t become dangerous on the day of an inspection. It wears a little every week. The cheapest and least stressful way to handle that is to check it yourself on a regular schedule.

A sensible routine looks like this:

  1. Monthly: check pressures when the tyres are cold, and look at each tyre’s tread and sidewalls.
  2. Every second month or before a long trip: measure depth with a gauge at three points across each tyre.
  3. Every 10,000 km or so: rotate the tyres. We’ve set out a rotation schedule for Australian drivers that fits around normal servicing.
  4. After any kerb strike or pothole hit: look for bulges and cuts, and check the steering still feels right.

When tread depth isn’t the whole story

A tyre can have plenty of tread and still be one you shouldn’t drive on. Advice from motoring bodies is that a tyre may show legal depth in the main grooves but still be dangerous because of uneven wear, deep cuts or structural damage to the sidewall. That fits the NSW wording, which says tyres must not have cracks or bumps or be worn unevenly.

Uneven wear

If the inside or outside edge is wearing faster than the middle, or you see feathering across the tread blocks, the tyre is telling you something about the vehicle. Often it’s alignment, sometimes pressures, sometimes worn suspension parts. Uneven wear is usually the first sign that something mechanical needs attention, long before the tread hits its limit. Our article on uneven tyre wear patterns shows what each pattern points to. A professional wheel alignment check is the usual next step when the wear is lopsided. To work out whether you need an alignment or a balance, these four checks will narrow it down.

Sidewall damage and bead leaks

Cuts, bulges and cracks on the sidewall don’t show up in a tread reading. Don’t try to judge them by depth. Read our guide to sidewall damage and when to replace, and if a tyre keeps losing air at the rim, our page on bead leaks explains the checks.

Tyre age

Tread depth also says nothing about how old the rubber is. Tyres that sit in the sun for years can harden even with plenty of tread. The date code on the sidewall tells you the build week and year. We explain the difference between the law and manufacturer advice on tyre age and how to read the code.

What fitting a new set looks like

You don’t need to wait for the indicators to show. Once you’re around 3mm, the sensible move is to choose your replacement and lock in a fitting time, so you’re not forced into whatever’s in stock the day a tyre fails an inspection or a puncture shows the damage.

Before you buy:

  • Find your tyre size. It’s printed on the sidewall, for example 265/60R18. Our guide to calculating tyre size for Australia helps if you’re thinking of changing size and want to stay within the limits.
  • Replace in pairs at least. Fit the new tyres on the rear axle if you’re only doing two, or follow your vehicle maker’s advice.
  • Think about the mix of driving you do. City commuting, highway runs, towing and dirt roads each suit different tyre types.
  • Consider an alignment. If your old tyres wore unevenly, fitting new ones without fixing the cause just repeats the problem.

Our perspective: check early, replace on your terms

We built Treadivo around a simple idea: replacing tyres shouldn’t be a scramble. The drivers who end up with the worst experience are the ones who find out at the last minute, when a fitter is booked out, the price is a guess, and the only tyre in stock is whatever’s on the shelf.

Our perspective: check early, replace on your terms — overview diagram

So our advice is to treat 1.5mm as the legal edge of the cliff and plan your purchase well back from it. Measure at the grooves, look at the whole tyre for uneven wear or damage, and set the replacement date while you still have choices. When you shop with us you can search by car model or tyre size, see itemised pricing with no hidden fees, and choose a local fitter. Our AI Tread Check gives you a quick read on your tyres from home, and the AR view lets you see how a new set looks on your car before you commit.

The point isn’t to sell you tyres early. It’s to make sure that when you do need them, buying and fitting takes minutes, not a week of phone calls.

— Areesh

Ready to replace? Book a fit in your city

If your tread is close to 3mm or the indicators are showing, you can browse tyres by size or car model, check out in about three minutes and get a same-day fitting confirmation from a local fitter. We also have city pages for tyre fitting in Melbourne and tyre fitting in Perth. Our range covers passenger, SUV and 4x4, light truck, commercial and motorcycle tyres, among others.

FAQ

It’s 1.5mm. The 1.6mm figure comes from UK and European rules and is repeated on many Australian sites. State rules, such as those published by Transport Victoria and the NSW Government, specify 1.5mm. In practice, a tyre near 1.6mm is so close to the limit that you should be replacing it anyway.

Does the minimum tread depth differ between states?

No. Victoria, NSW and Queensland all give 1.5mm for light vehicles, and WA and SA regulations deal with tyre tread on the same basis. Always check your own state’s transport authority for the current wording, particularly for modified vehicles or heavy vehicles.

Where on the tyre do I measure?

Measure in the principal grooves, the wide grooves across the part of the tread that normally touches the road. The depth must be present in a continuous band around the whole circumference. Take readings at several points across the width and around the tyre, and go by the lowest one.

We’d say yes, or at least start planning. RACV notes that wet grip and aquaplaning resistance fall away progressively, and that 3mm is a good point to check and act. Going earlier costs you a little tread. Going late can cost you stopping distance in the rain.

Is the 20 cent coin test accurate in Australia?

Not reliably. It’s borrowed from UK guidance based on a different coin and a different legal limit. A tread depth gauge or the wear indicators are better, and a fitter can check the whole tyre for uneven wear and damage at the same time.

Sources

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