Why Tread Depth Matters

Tyre tread channels water away from the contact patch between your tyre and road. When tread wears down, tyres cannot clear water effectively and aquaplaning (sliding on water) becomes a serious risk. Worn tyres significantly increase stopping distances.

Method 1: The Coin Test (Australia)

  1. 1

    Get a 20 cent coin

    The platypus bill on a 20 cent coin sits at approximately 3mm from the edge — a useful benchmark.

  2. 2

    Insert into the tread groove

    Push the coin into the tread groove with the platypus bill going in first. Check the main grooves across the tyre width.

  3. 3

    Read the result

    If you can see all of the platypus bill above the tread, your depth is below 3mm. Still legal but consider replacing soon. If you can see the number "20" clearly, the tread is very low. For the US, use a quarter coin — if you can see all of Washington's head, tread is below 4/32 inch.

Method 2: Tread Wear Indicators

  1. 4

    Find the wear indicator

    Look for a small raised bump or bar in the base of the tyre's main tread grooves. This is moulded into the tyre at the legal minimum tread depth (1.5mm in Australia, 1.6mm in UK and US).

  2. 5

    Compare indicator to tread

    If the wear indicator is flush with the tread surface, your tyres are at or near the legal minimum and must be replaced immediately.

Replace before the legal minimumMost tyre experts recommend replacing tyres at 3mm — not waiting until the legal minimum of 1.5mm. Braking distances increase significantly below 3mm, particularly in wet weather.

Check All Four Tyres

Check tread depth in three places across the tyre width (inside edge, centre, outside edge) and check all four tyres. Uneven wear can indicate alignment or suspension issues that a mechanic should look at.

Frequently Asked Questions

Check monthly when you check tyre pressure. Also check after any impact (hitting a kerb or pothole) and before long road trips.
Wear on outer edges only suggests under-inflation. Wear in the centre suggests over-inflation. One-sided wear suggests alignment problems. Patchy or cupping wear suggests suspension issues. Any unusual wear pattern warrants a mechanic's inspection.
Typically 40,000–80,000km depending on driving style, vehicle weight, road conditions and the tyre quality. Even if tread appears adequate, tyres should be replaced after 5–7 years as rubber degrades regardless of mileage.