With Geelong's winter rain making roads slicker than usual, now is a good time to think about how much grip is actually left in your tyres. Tread depth is one of the simplest things to check, yet it's often overlooked until a tyre fails an inspection or, worse, lets go on a wet road.
What the law actually requires
Across Australia, the legal minimum tyre tread depth is 1.5mm, measured across the full width of the tyre, including the shoulders. Drive below this and your car is considered unroadworthy, which can mean a defect notice, a fine, or a fail at your next roadworthy inspection.
But "legal" and "safe" aren't the same thing. Most tyre manufacturers recommend replacing tyres once tread drops to around 3mm, well before you get anywhere near the legal cut-off.
Why wet roads change the equation
Tread isn't just there for grip on dry bitumen — its main job in the wet is channelling water out from under the tyre so rubber can actually touch the road. As tread wears down, that channelling ability drops off fast. Once you're down near the legal minimum, braking distances in wet conditions can be roughly double what they'd be on a tyre with healthy tread. On a wet Princes Highway on-ramp or a rain-soaked roundabout, that difference can be the gap between stopping in time and not.
Checking your tread depth
You don't need special tools for a quick check:
- The coin test: Insert a 20-cent coin into the tread groove with the platypus's bill facing down. If you can still see the top of the bill, tread is getting low and it's worth getting checked professionally.
- Tread wear indicators: Most modern tyres have small raised bars moulded into the tread grooves. When the tread surface wears level with these bars, the tyre is at its wear limit.
- Check all four, and check across the tyre: Uneven wear (more on the inside or outside edge) can point to alignment or pressure issues rather than just age.
Other habits that help in winter
Tread depth is only part of the picture. A few extra checks make a real difference through the colder, wetter months:
- Keep tyre pressures at the manufacturer's recommended setting — underinflated tyres wear unevenly and lose grip faster.
- Rotate tyres roughly every 10,000km so wear stays even across the set.
- Watch for feathering, cupping, or patchy wear, which often signal a wheel alignment issue rather than a tyre problem.
- Don't ignore vibration through the steering wheel; it's frequently an early sign of wear or balance issues.
A note for heavier vehicles
If you drive a ute, wagon, or anything that regularly carries a full boot or a trailer, tread wear can creep up faster than expected because of the extra load on the tyres. It's worth checking tread depth a little more often on these vehicles, especially heading into a wetter stretch of weather.
If you're not sure how your tyres are tracking, it's a quick job to have them checked properly. The team at Global Tyres Geelong, at 246 Thompson Rd in North Geelong, can measure your tread depth, check your pressures, and run a wheel alignment check while you wait — a handy bit of peace of mind before the wet weather really sets in.