What Is the Legal Tyre Tread Depth in Australia?

The legal minimum tyre tread depth in Australia is 1.5 mm across the face of the tread — the same in every state and territory. New tyres start with roughly 8 mm. Wear bars moulded into the grooves show when you've reached the limit, but wet-weather grip falls away well before that, which is why many tyre specialists recommend replacing at around 3 mm.

What does the law say?

Australian road rules require at least 1.5 mm of tread in the principal grooves — anywhere the tyre touches the road. A tyre below that is unroadworthy: penalties vary by state, a defect notice can take the car off the road, and driving on bald tyres can complicate an insurance claim after a crash. The rule applies to any tyre in service, including a spare once it's fitted.

How do you check tread depth?

• Tread wear indicators — small raised bars moulded across the grooves at the legal limit. Tread flush with the bars means the tyre is done, today.

• A tread depth gauge — accurate, and typically under $15 at any auto store. Measure the inner, centre and outer grooves of each tyre.

• The 20-cent test — place an Australian 20-cent coin in the groove. If the tread doesn't reach the platypus' bill (about 3 mm in), you're in the replacement-planning zone even if you're still legal.

Why 1.5 mm is a floor, not a target

Tread depth is what clears water from under the contact patch. Independent wet-braking tests have repeatedly shown stopping distances stretch sharply once tread drops below about 3 mm, and the aquaplaning threshold falls with it. Legal-but-low tread works acceptably in the dry — the first heavy downpour is where it bites.

What does uneven wear tell you?

• Worn shoulders, healthy centre — chronic under-inflation. The classic silent killer; live monitoring catches it early.

• Worn centre, healthy shoulders — over-inflation.

• One edge worn — wheel alignment is out.

• Flat spots or scalloping — suspension components or balance.

Tread tells you how a tyre has lived. So does its age — a tyre can be legal on tread and still dangerous on years. Our guide to tyre age and the DOT date code covers that half of the story.

Frequently asked questions

How often should I check tread depth?

Monthly is ideal, and always before a long trip — it takes one minute with the pressures you should already be checking. Passenger tyres typically last 40,000–60,000 km, but load, pressure discipline and driving style swing that widely.

Is the legal limit different for 4WDs or caravans?

No — 1.5 mm applies to light vehicles across the board in Australia, caravans included. Heavily loaded vans in wet conditions are exactly where extra margin above the minimum earns its keep.

Do I have to replace tyres in pairs?

Best practice is at least in pairs across an axle so grip stays balanced side-to-side, with the newer pair fitted to the rear on most vehicles. Your tyre shop can advise for your specific setup.

Keep every tyre honest between inspections — the Flatmate range watches pressure and temperature 24/7. Call 0448 626 964 with any questions.