Your tyres have one job: keeping your car connected to the road. And the part doing most of the work is the tread — those grooves cut into the rubber that channel water away and grip the surface beneath you. As tread wears down, your car takes longer to stop, is more likely to skid in the wet, and becomes far more prone to aquaplaning. The good news? Checking your tread takes less than five minutes, and you probably have the only tool you need in your pocket.
What the law says
In Australia, the legal minimum tread depth is 1.5 millimetres across the face of the tyre. Drive on anything less and your car is unroadworthy — you risk a fine, losing demerit points, and potentially having an insurance claim knocked back if worn tyres contributed to a crash.
But here's the thing: 1.5mm is a legal floor, not a safety target. Tyre performance in the wet drops off noticeably well before you reach the minimum. Most tyre manufacturers and safety bodies suggest replacing tyres at around 3mm, because braking distances on wet roads grow significantly between 3mm and 1.5mm. New tyres typically start life with about 8mm of tread, so by the time you're at 3mm, you've used most of the tyre's safe working life.
The 20-cent coin test
You don't need special equipment for a quick check. Grab an Australian 20-cent coin and slot it into one of the main tread grooves. If the tread doesn't reach the bill of the platypus, you have less than about 3mm remaining — time to start planning for new tyres.
For a more precise reading, a tread depth gauge costs only a few dollars from any auto parts store. Whichever method you use, check each tyre in at least three spots: the inside edge, the centre, and the outside edge.
Don't forget the wear indicators
Every tyre also has built-in tread wear indicators — small raised bars sitting inside the main grooves, usually marked on the sidewall with a little triangle or the letters TWI. When the surrounding tread wears down level with these bars, the tyre is at the legal limit and must be replaced. If the bars are flush with the tread, don't wait — the tyre is done.
Why checking multiple spots matters
Tyres rarely wear perfectly evenly, and where the wear shows up tells a story:
- Worn edges, healthy centre — often a sign of long-term underinflation.
- Worn centre, healthy edges — usually overinflation.
- One edge worn much more than the other — commonly points to a wheel alignment issue.
- Patchy or scalloped wear — can indicate a balance problem or worn suspension components.
So a tread check is really two checks in one: how much rubber is left, and whether something else is quietly eating your tyres. Catching an alignment or pressure problem early can add thousands of kilometres to a tyre's life.
Make it a habit
A monthly tread check — ideally at the same time you check tyre pressures — is one of the simplest safety habits any driver can build. Do it when the tyres are cold, give each tyre a quick visual once-over for cuts, cracks or embedded stones while you're there, and don't forget the spare.
If your 20-cent coin is telling you it's nearly time, or your tread is wearing unevenly and you're not sure why, the team at Global Tyres Geelong in North Geelong can measure your tread properly, check your alignment, and help you work out whether your tyres have another season in them or are due for replacement.