If you're selling a registered car in Victoria, re-registering one, or bringing a vehicle in from interstate, you'll need a Certificate of Roadworthiness. Tyres and wheels are one of the easiest areas to get pulled up on — and one of the easiest to check yourself before you book the test.
Here's what a licensed vehicle tester is looking at, and how to spot the problems early.
Tread depth: 1.5mm in the principal grooves
Victoria's vehicle standards require a minimum tread depth of 1.5mm in all principal grooves — the wide grooves usually running through the centre of the tread. Secondary grooves, which are shallower by design, aren't measured the same way.
Most tyres have built-in tread wear indicators: small raised bars sitting in the bottom of the principal grooves. If the tread has worn flush with those bars, the tyre is at the limit and won't pass. You don't need a gauge to check — run your finger across and look for whether the bars are sitting level with the surrounding rubber.
Worth saying plainly: 1.5mm is the legal minimum, not a safe target. Wet-weather grip drops off well before a tyre reaches that point. If you're replacing tyres anyway, doing it at around 3mm is a far better decision than squeaking through a test at 1.6mm.
Uneven wear across the tread
A tyre must not have excessive uneven wear across its width. This catches a lot of otherwise-healthy cars. A tyre can have plenty of tread in the middle but be worn to the canvas on one shoulder — and that's a fail.
Uneven wear is usually a symptom rather than the problem itself. Wear on both outer edges often means chronic under-inflation. Wear down the centre strip suggests over-inflation. Wear concentrated on one edge, or a feathered edge you can feel when you run your hand across the tread, usually points to wheel alignment.
The catch is that fitting new tyres without fixing the cause just resets the clock. If your old tyres wore unevenly, get the alignment checked at the same time.
Damage: cuts, cracks and bulges
Testers will look over the sidewalls and tread for deep cuts, cracks, bulges or anything else likely to cause the tyre to fail. A bulge in the sidewall means the internal structure has been damaged — often from a solid kerb strike or pothole — and that tyre needs replacing, regardless of how much tread is left.
Fine surface cracking in the sidewall rubber is common on older tyres that have spent years in the sun. Light crazing isn't automatically a fail, but deep cracks are, and they're a good sign the tyre has aged out.
Repairs done the right way
A properly repaired puncture is fine. A plug jammed in from the outside at the roadside is not — that's considered an emergency measure to get you to a workshop, not a permanent fix.
For a repair to be acceptable, the tyre has to come off the rim so the inside can be inspected, and the patch or plug vulcanised from the inside. Repairs are only permitted in the crown area — the central tread band. Punctures in the shoulder or sidewall can't be repaired at all, and tyres marked "do not repair" are exactly that.
The things people forget
- Matching tyres on an axle. Mixing sizes, constructions or wildly different tread patterns across the same axle causes problems.
- Load and speed ratings. Tyres need to be rated appropriately for the vehicle. Fitting something cheaper with a lower load rating than the placard specifies can fail.
- Run-flat tyres. These have extra requirements — the right rim type, and a working tyre pressure monitoring system, since a deflated run-flat gives you almost no warning otherwise.
- Valve caps. A small thing, but they're meant to be fitted. They keep grit out of the valve.
- Wheels themselves. Cracked, buckled or badly damaged rims are a fail on their own.
A quick pre-test routine
Give yourself ten minutes in the driveway before you book. Check the tread wear indicators on all four tyres. Run your hand across each tread looking for feathering or a step in the wear. Look along both sidewalls of every tyre, inner face included — turn the steering to full lock to see the fronts properly. Check the pressures against the placard, usually on the driver's door jamb or inside the fuel flap.
A roadworthy certificate in Victoria is valid for a limited window from the date of issue, so it's worth sorting out any tyre issues before the inspection rather than paying for a re-test. If you'd like a second set of eyes on your tread, wear patterns or alignment before you book, the team at Global Tyres Geelong in North Geelong is happy to take a look.